Program Nanomechanical Testing In Materials Research and Development October 9-14, 2011 Lanzarote, Canary Islands, Spain Conference Chair: Prof. Dr. Gerhard Dehm Department Materials Physics, University of Leoben and Erich Schmid Institute of Materials Science of the Austrian Academy of Science Engineering Conferences International 32 Broadway, Suite 314 - New York, NY 10004, USA Phone: 1 - 212 - 514 - 6760, Fax: 1 - 212 - 514 - 6030 www.engconfintl.org – [email protected]
Transcript
Program
Nanomechanical Testing In Materials Research and Development
October 9-14, 2011 Lanzarote, Canary Islands, Spain
Conference Chair:
Prof. Dr. Gerhard Dehm Department Materials Physics, University of Leoben
and Erich Schmid Institute of Materials Science of the Austrian Academy of Science
Engineering Conferences International 32 Broadway, Suite 314 - New York, NY 10004, USA Phone: 1 - 212 - 514 - 6760, Fax: 1 - 212 - 514 - 6030
Engineering Conferences International (ECI) is a not-for-profit global engineering conferences program, originally established in 1962, that provides opportunities for the exploration of problems and issues of concern to engineers and scientists from many disciplines.
ECI BOARD MEMBERS
Barry C. Buckland, President
Peter Gray
Michael King
Raymond McCabe
David Robinson
Jules Routbort
William Sachs
Eugene Schaefer
P. Somasundaran
Deborah Wiley
Chair of ECI Conferences Committee: William Sachs
ECI Technical Liaison for this conference: Herman Bieber
Sunday, October 9, 2011 15:00 – 18:00 Registration 18:00 – 19:00 Welcome Reception 19:00 – 20:30 Dinner Opening Session 20:30 – 20:40 Welcome Conference Chair: Gerhard Dehm, University of Leoben, Austria 20:40 – 21:20 Topological optimization, fabrication, and characterization of 3-dimensional micro/nanoscale materials (Plenary)
Kevin Hemker, Johns Hopkins University, MD, USA 21:20 - 22:00 Measuring nanoscale deformation in complex materials with synchrotron radiation
X-rays (Plenary) Oskar Paris, University of Leoben, Austria
Notes
• Breakfast will be served in the restaurant each day. • Lunch locations will be announced on site but will generally be outside. • Dinners will be in the restaurant except for the Fish BBQ banquet which will be outside. • Technical and poster sessions will be in the Tagororo meeting room. • Audiotaping, videotaping and photography of presentations are prohibited. • Speakers – Please have your presentation loaded onto the conference computer prior to the session start
(preferably the day before). • Speakers – Please leave at least 3-5 minutes for questions and discussion. • Please do not smoke at any conference functions. • Turn your mobile telephones to vibrate or off during technical sessions. • Be sure to make any corrections to your name/contact information on the Master Participant List or
confirm (by your initials) that the listing is correct. A corrected copy will be sent to all participants after the conference.
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Monday, October 10, 2011 07:30 – 09:00 Breakfast buffet Micromechanics, Fracture and Fatigue 09:00 – 09:30 Nanomechanical testing of materials and thin films with the bulge test (Invited)
Mathias Göken, University of Erlangen-Nürnberg, Germany 09:30 – 09:50 Initial plasticity of thin wires in torsion under forward and reversed loading (R)
Andy Bushby, Queen Mary University of London, UK 09:50 – 10:10 Small scale plasticity of silicon as a function of electronic doping (R)
Rudy Ghisleni, Laboratory for Mechanics of Materials and Nanostructures – EMPA, Switzerland
10:10 – 10:30 Effects of constraints in plasticity on cleavage fracture of tungsten single
crystalline samples (R) Stefan Wurster, Austrian Academy of Sciences, Austria
10:30 – 11:00 Coffee break 11:00 – 11:30 Yield and plastic flow in small volumes in soft metals in tension and flexure
(Invited) David Dunstan, Queen Mary University of London, UK
11:30 – 12:00 Ductibility in highly nanotwinned copper – myth or reality? (I)
Andrea Hodge, University of Southern California, CA, USA 12:00 – 12:20 Ultra-high strain hardening in nanocrystalline palladium thin films with nanotwins:
an experimental study coupled to a phenomenological analytical model (R) Marie-Stephane Colla, University Catholique de Louvain, Belgium
12:20 – 12:40 Fracture testing – From the microscale to the macroscale (R) David Armstrong, University of Oxford, UK 12:40 – 13:00 Hydrogen embrittlement characterization of Fe-26Al-xCr Intermetallics with the aid
of in-situ nanoindentation Technique (R) Afrooz Barnoush, Saarland University, Germany
13:00 – 14:00 Lunch 14:00 – 16:00 Free time /ad hoc sessions 16:00 – 16:30 Afternoon coffee and snacks In-situ Testing 16:30 – 17:10 Uniaxial tensile testing of nanowires (Plenary)
Reiner Mönig, Karlsruhe Institute of Technology, Germany 17:10 – 17:30 Mechanical properties of Cu nanowires by in situ bending experiments (R)
Gunther Richter, MPI for Intelligent Systems, Germany 17:30 – 18:00 Micro-objects in-situ deformation of as a tool to uncover the role of dislocation
nucleation in the brittle-to-ductile transition in InSb semi-conductor (Invited) Ludovic Thilly, University of Poitiers, France
Monday, October 10, 2011 (continued) 18:00 – 18:20 Modifying mechanical properties on a nanometer scale by controlled annealing of
crystal defects (R) Daniel Kiener, University of Leoben, Austria
18:20 – 18:50 Tensile properties of nano-twinned Cu nano-pillars through in-situ mechanical
testing, electron microscopy, and atomistic simulations (Invited) Julia Greer, California Institute of Technology, USA
18:50 – 19:30 Poster Preview I 19:30 – 21:00 Dinner 21:00 – 23:00 Poster Session I with social hour
Tuesday, October 11, 2011 07:30 – 09:00 Breakfast Indentation I 09:00 – 09:40 Multiscale modeling of indentation: From atom to continuum (Plenary)
Marc Fivel, SIMaP-GPM2, France 09:40 – 10:00 Single crystal plasticity of titanium quantified through orientation informed
nanoindentation and crystal plasticity finite element simulation (R) Claudio Zambaldi, MPI for Iron Research, Germany
10:00 – 10:20 Elastic anisotropy of materials studied by nanoindentation and atomic force
acoustic microscopy Techniques (R) Kong Boon Yeap, Fraunhofer Institute for Nondestructive Testing, Germany
10:20 – 10:40 New method based on second harmonic detection to extract mechanical properties
from dynamic nanoindentation Tests (R) Jean-Luc Loubet, Ecole Centrale de Lyon, France
10:40 – 10:10 Coffee break 10:10 – 11:40 Mechanical properties mapping using probe experiments: Fact and fiction (Invited)
Warren C. Oliver, Nanomechanics Inc., TN, USA 10:40 – 12:00 In situ, elevated temperature nanoindentation: Best practices and case studies (R)
J.M. Wheeler, Mechanics of Materials and Nanostructures Laboratory – EMPA, Switzerland
12:00 – 12:30 Hot microcompression in vacuum up to 700°C (Invited)
S. Korte, University of Cambridge, UK 12:35– 13:30 Lunch 13:30 – 16:00 Free time /ad hoc sessions 16:00 – 16:30 Afternoon coffee with snacks Indentation II 16:30 – 17:00 Extracting mechanical properties of copper coatings on stiff and compliant
substrates by nanoindentation (Invited) Steve Bull, Newcastle University, UK
17:00 – 17:20 Twin boundary motion in MAX phase materials activated by nanoindentation (R)
Christoph Tromas, University of Poitiers, France 17:20 – 17:50 Nanoindentation strain-rate jump and long-term creep tests on nanocrystalline materials (R)
Verena Maier, University of Erlangen-Nuernberg, Germany 17:50 – 18:10 The interpretation of spherical indentation through multiscale material modeling:
from polycrystalline to single-crystal micro and nano-indentations (R) J. Alcala, Universitat Politecnica de Catalunya, Spain
Tuesday, October 11, 2011 (continued) 18:10 – 18:30 Nanoindentation based assessment of effective composite properties (R)
J. Nemecek, Czech Technical University in Prague, Czech Republic 18:30 – 18:50 Obtaining crystal plasticity parameters by inverse analysis of nanoindentation
results (R) Benjamin Schmaling, ICAMS – Ruhr-University Bochum, Germany
18:50 – 19:30 Poster Preview II 19:30 – 21:00 Dinner 21:00 – 23:00 Poster Session II
Wednesday, October 12, 2011 07:30 – 09:00 Breakfast Deformation Mechanisms I 09:00 – 09:40 Observation of dislocation-movement in passivated AL film using in situ
transmission electron microscopy nanoindentation (Plenary) Marc Legros, CEMES-CNRS, France 09:40 – 10:10 Size dependence of strength of metallic micropillars and the prerequisites for the
formation of stable pinning points (Invited) Seok-Woo Lee, Stanford University, CA, USA
10:10 – 10:40 Initial dislocation structures and boundary conditions in 3D discrete dislocation
dynamics simulations and their influence on micro scale plasticity (Invited) Christian Motz, Austrian Academy of Sciences, Austria
10:40 – 11:10 Coffee break 11:10 – 11:30 A simple stochastic model for yielding in specimens with a limited number of
dislocations (R) George M. Pharr, University of Tennessee, TN, USA
11:30 – 11:50 Influence of bulk pre-straining on the size effect in nickel compression pillars (R)
Andreas Schneider, Leibniz Institut fuer neue Materialien, Germany 11:50 – 12:10 Emergence of strain rate sensitivity in Cu nano-pillars: Transition from dislocation
multiplication to dislocation nucleation (R) Andrew T. Jennings, California Institute of Technology, USA
12:10 – 12:40 Exploiting interactions between indentation size and structure size effects to
determine the characteristic dimension of nano-structured materials by indentation (Invited) Nigel M. Jennett, National Physical Laboratory, UK
13:00 – 19:00 Boxed lunch and excursion to Timanfaya National Park 20:00 – 23:00 Dinner
Thursday, October 13, 2011 07:30 – 09:00 Breakfast Deformation Mechanisms II 09:00 – 09:40 3DXRD - Results, limitations and outlook (Plenary)
Dorte Juul Jensen, Risoe DTU, Denmark 09:40 – 10:00 Expected and unexpected plastic behavior at the micron scale: An in situ Laue
study (R) Christoph Kirchlechner, University of Leoben, Austria
10:00 – 10:30 Probing strain hardening behavior in multilayer nanolaminate systems (Invited)
David Bahr, Washington State University, WA, USA 10:30 – 11:00 Coffee break 11:00 – 11:30 Testing of Ultra-sensitive materials for nano-electromechanical system - USENEMS
(Invited) Peter Schaaf, TU Ilmenau, Germany
11:30 – 11:50 Yield and buckling in nanowire arrays (R)
Matthias Schamel, ETH Zuriich, Switzerland 11:50 – 12:20 Fracture toughness of micron-sized NiAl single crystalline cantilevers (Invited)
Karsten Durst, University of Erlangen-Nürnberg, Germany 12:20 – 12:50 Effect of ion irradiation on the micropillar compression of LiF single crystals
(Invited) Jon M. Molina-Aldareguia, IMDEA Materials Institute, Spain
13:00 – 14:30 Lunch 14:30 – 16:00 Free time /ad hoc sessions 16:00 – 16:30 Afternoon coffee with snacks New Instrumentations and Developments 16:30 – 16:50 Measuring substrate-independent elastic modulus of stiff and compliant films by
nanoindentation Holger Pfaff, Agilent Technologies, Germany 16:50 – 17:10 Compact test platform for in-situ materials characterization in various fields of
microscopy Stephan Fahlbusch, Alemnis GmbH, Switzerland
17:10 – 17:30 Recent applications of nanoindentation measurements and evolutions of
instrumentation Philippe Kempe, CSM Instruments SA, Switzerland 17:30 – 17:50 Innovations for mechanical testing at nanoscale Ude Hangen, Hysitron, USA 17:50 – 18:10 A simple new method to measure force displacement curves Stephan Kleindiek, Kleindiek Nanotechnik GmbH, Germany
Thursday, October 13, 2011 (continued)
18:10 – 18:30 Thermal drift in high temperature indentation: A non-displacement based approach Vincent Jardret, Michalex, France 18:30 – 18:50 TIP Radii effects on the failure produced in ultra-thin films by scratch testing Bryan Crawford, Nanomechanics Inc., USA 18:50 – 19:10 Nanomechanical Testing at high temperatures: New solutions for more accuracy Wolfgang Stein, SURFACE, Germany 19:30 – 22:00 Conference Banquet
Friday, October 14, 2011 07:30 – 09:00 Breakfast “Novel” Materials 09:00 – 09:40 A combinatorial approach using nano scanning calorimetry and x-ray diffraction to
study the effect of composition and quench rate on the crystallization of Au-Si-Cu metallic glasses during rapid heating (Plenary) Joost J. Vlassak, Harvard University, USA
09:40 – 10:00 The effect of topography features on modulus mapping of nanoscale interfaces in
a deep sea sponge (R) Igor Zlotnikov, MPI of Colloids and Interfaces, Germany
10:00 – 10:20 Temperature dependence of visco-elastic properties of polymer thin films using
nanoindentation (R) Diana Courty, ETH Zurich, Switzerland
10:20 – 10:40 Multiscale approach to plastic deformation of silicate glasses at the micron scale
(R) Etienne Barthel, CNRS / Saint-Gobain, France
10:40 – 11:30 General Discussion 12:00 – 13:30 Lunch and Departure
Abstracts
Nanomechanical Testing in
Materials Research and Development
October 9-14, 2011
Lanzarote, Canary Islands, Spain
Sunday, October 9, 2011 Opening Session
TOPOLOGICAL OPTIMIZATION, FABRICATION, AND CHARACTERIZATION OF 3-DIMENSIONAL MICRO/NANOSCALE MATERIALS
Kevin Hemker, Johns Hopkins University Dept Mechancial Engineering, 3400 N Charles St., Baltimore, MD, 21218, USA
Recent advances in computational capabilities and topological optimization methodologies for design of internal material architecture, coupled with the emergence of micro- and nanoscale fabrication processes, 3D imaging, and nanoscale testing methodologies, now make it possible to design, fabricate, and characterize disparate material systems with unprecedented control. This talk will describe a collaborative research project that links computational optimization with scalable 3D braiding and weaving technologies to design and fabricate structural components with dramatically higher permeability and stiffness. The design, optimization, fabrication and characterization of these structural materials occurs at three length scales: (i) the component macrostructure or architecture spans centimeters to meters; (ii) the architectural unit cells span tens of microns to millimeters; and (iii) the material microstructures within unit cell struts span nanometers to tens of microns. The highest level (component level) encompasses gradients in unit cell architecture, porosity, and composition as well as the creation of sandwich structures. The second level (architectural unit cells) employs architectural optimization to design the geometry of the braided/woven structure. Available degrees of freedom include: volume fraction, wire type and placement, wire geometry, and wire orientation in each of three directions. The smallest hierarchical level (strut shape and microstructure), focuses on vapor phase alloying of the wires after textile manufacturing. Vapor phase processing provides an opportunity to tailor the wires and struts at the micro- and nanoscale. The transformation of pure Ni wires to Ni-base superalloys imparts superior elevated temperature properties; the formation of intermetallic or ceramic coatings with different elastic constants allows one to tailor the second moment of inertia; and colossal carburization dramatically improves corrosion resistance. Once optimized and fabricated, these disparate material architectures must be characterized on all levels. Specialized techniques for characterizing the resulting 3D structures and properties will also be discussed.
Sunday, October 9, 2011 Opening Session
MEASURING NANOSCALE DEFORMATION IN COMPLEX MATERIALS WITH SYNCHROTRON RADIATION X-RAYS
Oskar Paris, Institute of Physics, Montanuniversitaet Leoben Franz-Josef-Strasse 18, Leoben, 8700, Austria
High brilliance synchrotron radiation from third generation sources has become an excellent tool to study deformation behaviour in complex materials such as in nanostructured engineering composites or in hierarchically structured biological tissues. Two recent developments are particularly noteworthy: i) the availability of X-ray microbeams with beam sizes down to the sub-micrometer scale allows mapping of local strains with unprecedented spatial resolution, and ii) diffraction experiments with high time resolution permit the in-situ observation of strain development with high temporal resolution. This lecture provides a general overview of the current experimental possibilities, and will briefly review some recent applications to hierarchical deformation studies in biological tissues. Two examples from own work on complex engineering materials will be discussed in more detail. The first example deals with the investigation of single carbon fibres under bending load with scanning X-ray microbeam diffraction. A beam of 100 nm width allows mapping of the local strains across the bent fibres and thus, the direct observation of carbon crystallite buckling at the nanometre scale [1]. The second example deals with the deformation of nanoporous silica materials exhibiting a highly ordered honeycomb like nanostructure. Deformation of these materials is caused by the adsorption and condensation of fluids in the narrow pores of about 10 nm diameter. In-situ observation of the pore lattice strains as a function of fluid pressure provides deep insights into the complex interactions between solid pore walls and the fluid phase behaviour [2], and allows to extract nanomechanical properties of the materials [3]. [1] D. Loidl, O. Paris, M. Burghammer, C. Riekel and H. Peterlik, Phys. Rev. Lett. 95, 2005. 225501. [2] G. Günter, J. Prass, O. Paris, M. Schoen, Phys. Rev. Lett. 101 (2008) 086104. [3] J. Prass, D. Müter, P. Fratzl, O. Paris, Appl. Phys. Lett. 95 (2009) 083121
Monday, October 10, 2011 Micromechanics, Fracture and Fatigue
NANOMECHANICAL TESTING OF MATERIALS AND THIN FILMS WITH THE BULGE TEST
Mathias Göken, Department of Materials Science and Engineering, Institute I, University Erlangen-Nürnberg, Germany
Bulge testing is an attractive testing method to measure the mechanical properties of thin films and materials on the nanoscale. In a bulge-test a freestanding membrane is pressurized from one side by a gas or a liquid and the deflection of the membrane is measured. Such a test allows measuring the plastic deformation properties i.e. yield strength and residual stresses of thin films and to calculate stress-strain curves. Next to this a bulge-test can also be used to measure the fracture toughness of thin films and recently also the first fatigue tests have been performed with a bulge test. A specially designed bulge test setup has been developed in Erlangen [1] which is based on a gas-pressuring system which allows very flexible loading and unloading cycles of the membrane. The deflection is measured with a very simple and reliable autofocus system. This system can be integrated into an atomic force microscope, AFM to allow in-situ investigations of the deformation processes of pressurized membranes. The membranes typically are produced by lithographic techniques since good adhesion of the film to the supporting substrate is necessary. By testing thin copper films with a thickness down to only 500 nm very good agreement with the commonly accepted 1/h thickness dependence for the yield strength is obtained. The bulge-test also allows testing of the fracture behaviour by introducing slits in the membrane with a Focused Ion Beam (FIB) system [2]. The fracture toughness of LPCVD (Low Pressure Chemical Vapor Deposited) silicon nitride thin films was found to be independent of the film thickness at a level of 6.3 MPam1/2. First fatigue tests have been performed on freestanding Au films and on Au films deposited on a silicon nitride film up to 100.000 cycles which also will be discussed. The residual stresses of the films grew toward increasingly compressive stresses for both cases. However the failure mechanisms are clearly different. The AFM shows the formation of deformation structures and indicate grain growth on the surface. The paper will give an overview of different bulge test options. The different size effects as found by this tests will be discussed in detail. [1] E.W. Schweitzer, M. Göken, Journal of Materials Research 22, 2902-2911 (2007) [2] B. Merle, M. Göken, Acta Materialia 59, 1772-1779 (2011)
Monday, October 10, 2011 Micromechanics, Fracture and Fatigue
INITIAL PLASTICITY OF THIN WIRES IN TORSION UNDER FORWARD AND REVERSED LOADING
Andy Bushby, Queen Mary University of London Mile End Road, London, E1 4NS, UK
T: +44 20 7882 5276, F: +44 20 7882 3390, [email protected] Nicola Schmitt, Karlsruhe Institute of Technology David Dunstan, Queen Mary University of London
Oliver Kraft, Karlsruhe Institute of Technology
The plasticity of materials and structures in the micron and submicron range is of great interest at the present time. Methods of lithography and focus ion beam milling allow structures to be formed with structural dimensions of the order of a micron. Similarly, the same techniques can be used to construct testing systems small enough to fit in the electron microscope. However, few of these methods have the sensitivity to detect the elastic limit and very early stages of plasticity. Here we report experimental data on the torsional loading of long thin wires with micro-strain resolution. Copper and gold wires with diameters ranging from 10 microns to 150 microns were tested using a load-unload method, twisting the wire to a give angle and then untwisting and noting the angle at which the wire hangs freely. Reversal of the loading direction was possible through rotation of the wire in the opposite direction. The elastic limit of the wires was clearly identified. Below the elastic limit no creep was observed in the wire while held under load but was obvious once plasticity was initiated. The yield strain in both copper and gold wires appeared to be similar. However the gold wires displayed a much higher rate of work hardening. Increasing the grain size for copper wires decreased the yield strength, as expected from the Hall-Petch behaviour. Decreasing wire diameter increased the yield strength but reduced the rate of work hardening for both copper and gold wires. On reversing the loading the reduced yield strength was associated with a reduction in the Bauschinger effect for copper wires, while in gold wires the effects were less prominent. The sensitivity of these experiments allows plasticity to be explored at plastic strains more than two orders of magnitude lower than conventional tests.
Monday, October 10, 2011 Micromechanics, Fracture and Fatigue
SMALL SCALE PLASTICITY OF SILICON AS A FUNCTION OF ELECTRONIC DOPING
Rudy Ghisleni, Laboratory for Mechanics of Materials and Nanostructures - EMPA Feuerwerkerstrasse 39, Thun, 3602, Switzerland
T: +41332283703, F: +41332284490, [email protected] J. Rabier, Départment de Physique et Mécanique des Matériaux, Institut P', UPR 3346 - CNRS -
Université de Poitiers - ENSMA, F-86962 Chassenenuil-Futuroscope Cedex J.L. Demenet, Départment de Physique et Mécanique des Matériaux, Institut P', UPR 3346 - CNRS -
Université de Poitiers - ENSMA, F-86962 Chassenenuil-Futuroscope Cedex J. Michler, Laboratory for Mechanics of Materials and Nanostructures - EMPA
There are two ways to lower the brittle ductile transition temperature (BDTT) of brittle materials: by applying a hydrostatic pressure superimposed to the stress required for plastic deformation or by reducing drastically the sample dimensions. Rabier et al. have contributed to explore the original and somehow unexpected plasticity mechanisms of materials below the BDTT by using deformation under confining pressure. In particular, in silicon, a high stress regime has been evidenced which is controlled by movement of perfect shuffle dislocations [J. Rabier et al. (2010), DOI: 10.1016/S1572-4859(09)01602-7]. On the other hand, the study of silicon nanopillars plasticity under uniaxial compression at room temperature (and a strain rate of 1-5 x 10-3) has shown that pillars having a diameter larger than a critical one are brittle whereas those having a smaller diameter exhibit a ductility which compares to that of metallic materials. The critical diameter has been found to be between 310 and 400nm [F. Östlund et al. (2009), DOI: 10.1002/adfm.200900418].
At these temperature and stress levels, effects which have been neglected or considered as “academic” can become relevant such as the electronic effects on dislocation movements and plastic deformation. The aim of this work is: 1) to confirm that perfect shuffle dislocations control the plasticity of silicon nanopillars at high stress; 2) to determine the effect of doping on the yield stress and on the brittle to ductile transition diameter of silicon nanopillars (doping affects the Fermi level position and thus the staking fault energy).
The mechanical tests are conducted on <123> oriented silicon single crystal nanopillars with diameters ranging from 500 nm to 2 μm obtained by focused ion beam machining. Wafers with different electronic doping are tested: intrinsic (P doped, Nn <= 1014 cm-3); n type (P doped, Nn = 6*1018 cm-3), and p type (B doped, Np = 1*1018 cm-3). Lowering the strain rate at 6.7 x 10-4 s-1 and orienting the pillar for single slip deformation allowed increasing the critical diameter for the intrinsic Si wafer to 850 nm at room temperature, at a yield strength measured in 7 GPa. The doped pillar presented a 10% increase in the yield strength, more statistic* is needed before drawing any conclusion on the effect of the electronic doping on the plastic deformation.
*more experiments will be conducted before the conference will take place
Monday, October 10, 2011 Micromechanics, Fracture and Fatigue
EFFECTS OF CONSTRAINTS IN PLASTICITY ON CLEAVAGE FRACTURE OF TUNGSTEN SINGLE CRYSTALLINE SAMPLES
Stefan Wurster, Erich Schmid Institute of Materials Science of the Austrian Academy of Sciences Jahnstrasse 12, Leoben, Styria, 8700, Austria
T: +43(0)3842-804-325, F: +43 3842 804 116, [email protected] Christian Motz, Erich Schmid Institute of Materials Science of the Austrian Academy of Sciences
Reinhard Pippan, Erich Schmid Institute of Materials Science of the Austrian Academy of Sciences
Cleavage fracture of body centered cubic metals is not yet fully understood. Leaving aside perfectly brittle materials, where fracture is associated with the breakage of atomic bonds, this investigation focuses on single crystalline tungsten, a semi-brittle material. The answer on the question, whether a material has to be considered brittle or semi-brittle is given by the competition of crack tip plasticity and breaking of atomic bonds and this work shall present some hints on what is really taking place at the crack tip. Using µm-sized fracture experiments, it is possible to manipulate directly the “mobility“ of dislocations / activity of dislocation sources due to a change in backstress and thereupon, to determine the influence of plasticity on cleavage fracture. The work is performed by utilization of two different types of experiments, bending and tensile testing, and secondly by different sample dimensions. Both ways change the stress distribution within the samples. Shielding dislocations are piled up close to the neutral axis within a bending sample, resulting in a backstress acting on a dislocation (source) – whereas they can move more easily through tensile samples. This affects the fracture behaviour: For tungsten single crystalline samples, stable crack growth was observed when loading notched cantilevers, while fracture was more likely to be unstable for tensile samples. Therefore, we assume for single crystalline tungsten that anti-shielding dislocations let the crack propagate [1]. Previous work of various scientific groups using such small-scaled fracture experiments of brittle rely on linear elastic fracture mechanics. Hence, emphasis will also be put on the evaluations basing on elastic-plastic fracture mechanics.
[1] P.B. Hirsch, A.S. Booth, M. Ellis, S.G. Roberts, Dislocation-driven stable crack growth by microcleavage in semi-brittle crystals, Scripta Metallurgica et Materialia, 27 (1992) 1723-1728
Monday, October 10, 2011 Micromechanics, Fracture and Fatigue
YIELD AND PLASTIC FLOW IN SMALL VOLUMES IN SOFT METALS IN TENSION AND FLEXURE
D.J. Dunstan, Queen Mary University of London School of Physics, London, E1 4NS, UK
T: +44 207 882 3687, F: +44 208 981 9465, [email protected] J. Galle, Queen Mary University of London
X.D. Hou, National Physical Laboratory A.J. Bushby, Queen Mary University of London
A detailed study of nickel and copper foils in flexure and thin copper wires in tension is reported. Yield points and accurately linear strain-hardening are observed. The data shows, in agreement with the classic studies of Fleck et al. (1994) and Stölken and Evans (1998), that the strain-hardening increases with strain-gradient. It is close to zero in all diameter wires in tension, while increasing rapidly in foils in flexure as the thickness goes from 150μm to 10μm. Fleck et al. and St ölken and Evans interpreted this behaviour within the framework of strain-gradient plasticity theory, according to which it is the density of geometrically necessary dislocations (determined by the strain gradient) which is responsible for the increase in strain hardening. Copper and nickel gives results in quantitative agreement, which points towards a general phenomenon rather than a dependence on material parameters.
Our data also show that the yield strain increases in both the wires in tension and the foils in flexure as the size is decreased. The influence of grain size is particularly interesting. It contributes to both yield strain and strain-hardening in exactly the same way as the diameter or thickness. Since the grain size does not affect the strain gradient, this creates a difficulty for some formulations at least of the strain-gradient theory.
N. A. Fleck, G. M. Muller, M. F. Ashby and J. W. Hutchinson, Acta Metall. Mater. 42, 475 (1994).
J. S. Stölken and A. G. Evans, Acta Mater. 46, 5109 (1998).
Monday, October 10, 2011 Micromechanics, Fracture and Fatigue
DUCTILITY IN HIGHLY NANOTWINNED CU - MYTH OR REALITY?
Andrea M Hodge, University of Southern California 3650 McClintock Ave, OHE 430, Los Angeles, CA, 90089, USA
T: 2137404225, F: 2137408071, [email protected] Timothy Furnish, University of Southern California
Troy Barbee, Lawrence Livermore National Laboratory Julia Weertman, Northwestern University
In this talk ductility of highly nanotwinned Cu will be discussed. Tensile tests were performed at various strain rates at both room and liquid nitrogen temperatures on nanostructured high purity (99.999%) copper foils ~ 170 microns thick containing highly aligned nanotwins. Samples were produced using interrupted magnetron sputtering .Higher ductility and strength were observed for all samples tested at liquid nitrogen which was attributed to the increase number of observed shear bands and to changes in the material's heat capacity. An extensive microstructural analysis will be presented.
Monday, October 10, 2011 Micromechanics, Fracture and Fatigue
ULTRA-HIGH STRAIN HARDENING IN NANOCRYSTALLINE PALLADIUM THIN FILMS WITH NANOTWINS: AN EXPERIMENTAL STUDY COUPLED TO A PHENOMENOLOGICAL ANALYTICAL
MODEL
Marie-Stéphane Colla, Université catholique de Louvain Place Sainte-Barbe, 2, Louvain-la-Neuve, 1348, Belgium
T: 003210479250, F: 003210472402, [email protected] B. Wang, H. Idrissi, D. Schryvers, EMAT, University of Antwerp, Belgium
G. Guisbiers, Université catholique de Louvain, Belgium J.P. Raskin, Université catholique de Louvain, Belgium T. Pardoen, Université catholique de Louvain, Belgium
Nanocrystalline metallic films suffer from a lack of ductility due to poor strain hardening capacity. A very large strain hardening capacity in ~30 nm grain size Pd thin films has been recently measured owing to on-chip nanomechanical tensile testing. The high strain hardening capacity is preserved for film thickness down to 80 nm. In addition to tensile tests, relaxation experiments were performed and show large strain rate sensitivity.
The impact of a 5 nm-thick chromium confinement layer on the Pd properties was investigated. The ductility is enhanced from 5% to more than 10% by removing the Cr layer. The Cr confinement layer induces early fracture and influences the plastic behaviour of Pd films by preventing dislocations escape through free surface. The ductility variation of Pd film is related to the imperfection sensitivity and further rationalized using a statistical Weibull-type analysis.
Transmission electron microscopy revealed the presence of coherent growth twins in about 20% of the grains, offering additional barriers to dislocation motion as well as sources for dislocation storage and multiplication. The coherence of twin boundaries disappears when plastic deformation exceeds a few percents. The dislocation/twin boundary interactions, involving the creation of sessile dislocations, have been characterized by high resolution transmission electron microscopy. These interactions partially explain the observed high strain hardening capacity of Pd films. The second origin for the high strain hardening capacity results from microstructure heterogeneities with softer and harder grains, leading to a wide elastoplastic transition.
These two contributions constitute the main ingredients of an elementary multigrain homogenization model which provides a rational prediction for the evolution of the strain hardening capacity. The impact of confinement originated from the backside ultra-thin Cr layer is included in the model as well.
Monday, October 10, 2011 Micromechanics, Fracture and Fatigue
FRACTURE TESTING – FROM THE MICROSCALE TO MACROSCALE
David E.J. Armstrong, University of Oxford, Department of Materials Parks Road, Oxford, OX1 4PH, United Kingdom
T: 0441865273768, F: +44 (0)1865 273789, [email protected] J. Gibson, University of Oxford, Department of Materials
A.J. Wilkinson, University of Oxford, Department of Materials S.G. Roberts, University of Oxford, Department of Materials
Fracture, especially brittle fracture, is often controlled by grain boundary behaviour. Until now measuring the fracture properties of single grain boundaries has required macroscopic bi-crystals which are expensive and may only be available in special orientations (if at all) . We have developed a technique using micro-cantilevers, manufactured using focussed ion beam machining and mechanically tested using a nanoindenter. At the small length-scale the balance between fracture and plasticity is altered so that quantitative analysis is limited to very brittle materials. We have used the method to measure the fracture toughness of selected grain boundaries of a wide range of types in bismuth-embrittled copper, characterised using EBSD and TEM-EDX. The results show measured fracture toughness values between 1 and 7 MPam0.5. This is in good agreement with the literature values, however no systematic dependence on crystallography, either in fracture plane of the boundaries or mis-orientation, was seen. Previous work on Cu-Bi bi-crystals has focused on “special” low sigma boundaries and this is the first time a large number of non-special boundaries have been tested.
The technique has also been applied to tungsten and tungsten 5wt% tantalum alloys for use in nuclear fusion applications. Four point bend tests have been performed on millimetre-scale specimens of W 5wt%Ta alloy, at temperatures from 290K to 1273K. Tests at temperatures up to 600K were seen to fracture in a brittle manner at a maximum longitudinal stress of approximately 700MPa; however the fracture plane tends to follow a path along the long axis of the bar, rather than straight through as seen in pure W alloys. EBSD shows that the path follows specific grain boundaries, which are weaker than the majority of the grain boundaries and the grain interiors. At temperatures above 600K the fracture mode changes from purely brittle to a mixed mode, with a yield stress of 1GPa and failure stress of 1.1GPa. Failure occurs by delamination of the specimen along the same types of boundaries as those seen to fail in a brittle manner at lower temperatures. Micro-mechanical testing of FIB machined cantilevers has been used to study the difference in fracture toughness of single boundaries in this alloy. It is found the fracture toughness varies from 1-20 MPam0.5 depending on the type of boundary tested. It is found the boundaries with the lowest fracture toughness , are those which dominate the fracture properties in the macroscale tests.
Monday, October 10, 2011 Micromechanics, Fracture and Fatigue
HYDROGEN EMBRITTLEMENT CHARACTERIZATION OF FE-26AL-XCR INTERMETALLICS WITH THE AID OF IN-SITU NANOINDENTATION TECHNIQUE
Afrooz Barnoush, Saarland University Department of Materials Science, Saarbrücken, Saarland, 66123, Germany
T: (+49) (681) 302-5163, F: (+49) (681) 302-5015, [email protected] Mohammad Zamanzade, Saarland University
Martin Palm, Max Planck Institute-Eisenforsch GmbH Horst Vehoff, Saarland University
Recently, Fe-Al base intermetallics attract more interest because of their low density, low cost of production, good corrosion resistance and acceptable mechanical properties up to moderate temperatures. The main limitation of these materials is their poor room temperature ductility due to hydrogen embrittlement. To improve the ductility of the alloys, it is convenient to add some special ternary alloying element.
In this work, we studied the influence of various chromium concentrations on the hydrogen embrittlement of Fe-26Al-xCr (001) single crystals using the nanoindentation technique. The Homogeneous Dislocation Nucleation (HDN) free energies were measured at both anodic and cathodic potentials. Cathodically charged Fe-26Al binary alloy or samples with low chromium concentrations exhibit susceptibility to hydrogen because nucleation of dislocations happen at low energies. In contrast, with addition of 5.0 at.% chromium, the HDN free energiy for the sample charged with hydrogen was similar with the anodically charged sample as well as theoretical value for hydrogen- free sample.
Moreover, we evaluated the effects of chromium concentrations on mechanical behaviors of alloys. The results indicate that the addition of chromium could increase both elastic modulus and nano-hardness of samples.
Key words: Nanoindentation, intermetallic compounds, mechanical properties, homogeneous dislocation nucleation (HDN) free energy and Fe3Al
Monday, October 10, 2011 In-situ Testing
UNIAXIAL TENSILE TESTING OF NANOWIRES
Reiner Moenig, Karlsruhe Institute of Technology Postfach 3640, Karlsruhe, 76021, Germany
T: +49 721 608 22487, F: +49 721 608 222347, [email protected] Andreas Sedlmayr, Steven Boles, Oliver Kraft, Karlsruhe Institute of Technology, Karlsruhe, Germany
Gunther Richter, Max Planck Institute for Intelligent Systems, Stuttgart, Germany
Nanowires are important components for many future technologies due to their unique physical properties which are often a consequence of their high surface areas or aspect ratios. Of particular interest for the reliable application of these materials is an understanding of their mechanical behavior. In order to mechanically characterize such systems, we have developed an experimental platform to perform tensile tests on nanowires inside a dual beam SEM/FIB. With this setup, nanowires with diameters down to 30nm can be tested and reliable stress-strain curves are recorded while the samples are imaged. The system uses piezoelectric actuators and a three-plate capacitor based transducer for applying and measuring force. High resolution strain data is obtained by the digital correlation of SEM images. In this system nanowires of different materials were investigated and results will be presented with a main focus on Au whiskers. In the Au whiskers, significant amounts of plasticity at high stresses in excess of 1GPa were found. The recorded data does not show a clear size dependence and a large scatter in the strength values suggests a statistical nature of the deformation process. In the SEM observations, different modes of failure were observed which appeared to be either brittle fracture or rupture after the thinning within an elongated region. Using EBSD, twins were found in almost all of the Au whiskers after testing. This observation indicates a transition in the deformation mechanism from the conventional dislocation mediated plasticity to partial dislocation activity and twinning for Au nanowires.
Monday, October 10, 2011 In-situ Testing
MECHANICAL PROPERTIES OF CU NANOWIRES BY IN SITU BENDING EXPERIMENTS
Gunther Richter, Max Planck Instiute for Intelligent Systems Heisenberstr. 3, Stuttgart, 70569, Germany
T: + 49 711 689 3587, F: + 49 711 689 3412, [email protected] Carola Schopf, University of Stuttgart
Matthias Schamel, University of Stuttgart Horst P. Strunk, University of Stuttgart
One dimensional structures have the prospect to change the physical properties of materials used in contemporary devices. Physical properties change with dimension and size enabling a tailoring of performance in nanometer sized devices. Ceramics, semiconductor and carbon materials are easily synthesized as one dimensional structures with typical diameters of several nanometers and length-diameter ratios of 1000:1. Only the metals as one of the oldest are difficult to fabricate in similar geometries. Recently we developed a process to grow perfect defect and flaw free nanowires with diameters of several ten nanometers, attached on substrates based on a process published in 1574. An initiator mediated filamentary crystal growth process based on the physical vapour deposition technique was developed. Typical diameters of the whiskers are 100 nm and lengths of up to 200 µm are observed, giving aspect ratios of up to 2000:1. Microstructure characterization of the nanowires was carried out predominantly by electron microscopy, revealing. a perfect, flaw and defect free bulk and surface crystal structure. No dislocations, stacking faults, or grain boundaries were detected. The growth direction is generally along the <110> crystallographic direction of the face centered cubic lattice. The nanowire surface is formed by low indexed crystallographic planes, the {111} and {100}. The overall geometry is dominated by the minimization in terms of surface energy and resembles the Wulff shape. it was not possible to detect impurities from the growth process on the surface or in the bulk of the nanowires. In situ bending experiments utilizing a micromanipulator inside a SEM allows mechanical probing of small volumes. This reduces the stochastic effect of slight deviations, especially on the surface facets, on the measured mechanical properties. Nanowhiskers which are attached on a standard TEM Cu grid were deflected in a cyclic manner with increasing load. After each deflection the load was reduced to check for plastic deformation. From the last bending experiment with elastic deformation the bending stress was calculated as a lower limit for the yield strength from the curvature of the deformed nanowhisker. The resulting bending stress reached values between 4 to 6 GPa. Almost no dependence on the nanowhisker diameter is observed. Knowing the crystallographic orientation of the whisker axis, a dislocation model is proposed for the deformation mechanism.
Monday, October 10, 2011 In-situ Testing
MICRO-OBJECTS IN-SITU DEFORMATION OF AS A TOOL TO UNCOVER THE ROLE OF DISLOCATION NUCLEATION IN THE BRITTLE-TO-DUCTILE TRANSITION IN INSB SEMI-
CONDUCTOR
Ludovic THILLY, University of Poitiers Institut Pprime, SP2MI, Bd Curie, Futuroscope Chasseneuil, 86962, France
T: 33 5 49 49 68 31, F: 33 5 49 49 66 92, [email protected] Rudy GHISLENI, Laboratory for Mechanics of Materials and Nanostructures, EMPA, CH-3602 Thun
Christophe SWISTAK, Laboratory for Mechanics of Materials and Nanostructures, EMPA, CH-3602 Thun Johann MICHLER, Laboratory for Mechanics of Materials and Nanostructures, EMPA, CH-3602 Thun
At ambient temperature and pressure, most of the semiconductor (SC) materials are brittle: this is the case of the III-V compound SC indium antimonide, InSb. In general, the brittle-to-ductile-transition (BDT) temperature is situated around 0.6Tm where Tm is the absolute melting temperature: for InSb, TBDT is around 150°C. The evolution, with temperature, of the elementary plasticity mechanisms (dislocations) has been studied in InSb by compression of macroscopic samples under hydrostatic pressure and subsequent transmission electron microscopy (TEM) analysis: in the ductile regime (above TBDT), perfect dislocations are observed while at low temperature only partial dislocations are observed. This change of deformation mechanism may explain the occurrence of the BDT: after the emission of the leading partial dislocation, the sources are shut off and crystal plasticity is restricted [Acta Mat, 58, 2010, 1418-1440].
To study the role of dislocation nucleation, InSb micro-pillars have been fabricated by FIB and in-situ compressed at room temperature in a SEM, in order to correlate the observation of slip traces at the pillars surface and features of the stress-strain curve. TEM thin foils have been cut out of the pillars to study the deformation microstructure.
Surprisingly, InSb pillars can be plastically deformed up to strains of 20% for diameters up to ~20µm. At larger diameters, the pillars become brittle without plasticity. Moreover, the yield stress increases when reducing the pillar diameter.
The TEM study of dislocations and the observation of slip traces at free surfaces show that increasing the surface-to-volume ratio of the pillars modifies the dislocation nucleation conditions and favours plasticity even at room temperature. The role of dislocation nucleation from free surfaces is thus discussed within the larger context of the micro-pillar compression technique and extrinsic size effects.
Monday, October 10, 2011 In-situ Testing
MODIFYING MECHANICAL PROPERTIES ON A NANOMETER SCALE BY CONTROLLED ANNEALING OF CRYSTAL DEFECTS
D. Kiener, Department of Materials Physics, Montanuniversität Leoben Jahnstr. 12, Leoben, 8700, Austria
T: +433842804412, F: +433842804116, [email protected] Z. Zhang, Erich Schmid Institute of Material Science, Austrian Academy of Sciences, Austria
S. Šturm, Institut Jožef Stefan, Ljubljana, Slovenia G. Dehm, Department of Materials Physics, Montanuniversität Leoben
It is well known that crystal defects are the essential ingredients to tailor mechanical properties of materials. While geometric size effects are a well established feature in small scale plasticity, a thorough understanding of the interaction of different strengthening mechanisms with limited sample volumes is still lacking. Moreover, common small scale sample fabrication techniques such as focused ion beam (FIB) shaping introduce unwanted defects into the material on top of the internal defect structure. Recently, it was reported that thermal annealing is capable of restoring pristine volumes from FIB fabricated molybdenum nano-pillars (M.B. Lowry et al., Acta Mater. 2010, 58: 5160). The aim of this work was to generalize this finding to fcc materials and larger size scales.
Controlled annealing experiments to reduce the defect density in FIB fabricated single crystal samples were performed in a vacuum furnace on micro-scale copper tensile samples and in-situ in the TEM for nano-scale copper compression samples as well as for a 100 nm thick freestanding single crystal copper film. The resultant crystal defects were characterized by advanced transmission electron microscopy (TEM) techniques such as atomic imaging and electron energy loss spectroscopy. Subsequently, the annealed specimens were subjected to mechanical testing in-situ in the scanning electron microscope (SEM) or TEM, respectively.
From these experiments, the operating deformation mechanisms such as homogenous dislocation nucleation in a defect free sample, spiral dislocation source operation for intermediate dislocation densities, and dislocation - defect interaction for distributed defects in the confined volume were identified and will be discussed in a quantitative manner. Moreover, by comparing the results to FIB prepared and not annealed specimens, the contribution of the afore mentioned FIB damage to the considered mechanism and related mechanical properties is evaluated and experimental strategies to avoid this FIB influence are discussed.
Monday, October 10, 2011 In-situ Testing
TENSILE PROPERTIES OF NANO-TWINNED CU NANO-PILLARS THROUGH IN-SITU MECHANICAL TESTING, ELECTRON MICROSCOPY, AND ATOMISTIC SIMULATIONS
Julia R Greer, Caltech 1200 E. California Blvd., MC 309-81, Pasadena, CA, 91125, USA
Jianyu Huang, Sandia National Lab Xiaoyan Li, Brown University
Huajian Gao, Brown University
Nano-twinned materials have attracted a lot of scientific interests because of their simultaneous attainment of high strength and ductility. We developed a fabrication technique that does not rely on the use of focused ion beam (FIB) to create vertically aligned cylindrical Cu nano-pillars with 50nm-250nm diameters containing periodic nano-twins with <111> orientations at different inclinations with 1nm-4nm spacings. In-situ uniaxial tensile testing of these structures provides a deeper understanding of plastic deformation mechanisms in nano-twinned metals, mainly benefiting from the well defined stress and strain distributions compared with commonly used in-grain nano-twins. With precise control of the microstructure, i.e. lamella thickness and twin boundary orientation, as well as pillar diameter, we are able to define the parameter space for dominant deformation mechanism and ultimate tensile strength. These nano-pillars were fabricated via electrodeposition through templated nanometer-sized cylindrical holes, and uniaxial tension and compression tests at a range of strain rates (1e-2 ~ 1e-4 sec-1) were conducted via in-situ mechanical testing. Microstructural changes due to plastic deformation were investigated via in-situ transmission electron microscopy (TEM). Results indicate a discrete transition from brittle fracture to localized plasticity via necking and lower strength with size reduction for orthogonally oriented twins. Pillars with slanted twin boundaries always sheared along twin boundaries during deformation at lower strengths. These findings are discussed in the framework of dislocation nucleation at the surfaces and subsequent glide along twin boundaries. This work sheds further light on deformation of nano volumes, where dislocation nucleation governs plasticity – as corroborated by molecular dynamics simulations.
Tuesday, October 11, 2011 Indentation I
MULTISCALE MODELING OF INDENTATION: FROM ATOM TO CONTINUUM
Marc C. FIVEL, SIMaP-GPM2 101 Rue de la Physique, BP 46, St Martin d'Heres, F-38402, France
In crystalline materials, indentation induced plasticity is a rather complex phenomenon that needs to be analysed at different scales in order to fully understand the underlying physics.
At the atomic level, the contact with the indenter induces dislocation nucleations that can be simulated by molecular dynamics (MD). Although the simulated volumes are very limited in sizes (typically (20nm)3), MD simulations give all the details of the nucleation process in term of shape and position of the indentation induced dislocations.
Such geometry can then be introduced in dislocation dynamics (DD) codes that can simulate at an upper scale (typically (2µm)3) the evolution of the dislocation microstructure during the indentation process. These simulations require coupling DD with a finite elements method (FEM) in order to enforce the boundary conditions. Although limited in term of indentation depth (typically 100nm), DD can be used to understand the ‘Indentation Size Effect’ which denotes an increase of the hardness when the indenter depth is decreased. DD simulations also give access to the surface relief, i.e. the indentation imprint left after the indenter removal.
At a higher scale FEM simulations can also simulate indentation test provided physical constitutive equations are implemented. At this scale, FEM both gives access to the indentation loading curve and to the surface imprint that can be compared to experimental data.
In this presentation, indentation of FCC metals like Cu or Ni is studied using these three numerical tools: MD, DD and FEM.
Tuesday, October 11, 2011 Indentation I
SINGLE CRYSTAL PLASTICITY OF TITANIUM QUANTIFIED THROUGH ORIENTATION INFORMED NANOINDENTATION AND CRYSTAL PLASTICITY FINITE ELEMENT SIMULATION
Claudio Zambaldi, Max-Planck-Institut für Eisenforschung Max-Planck-Str. 1, Düsseldorf, 40237, Germany
T: +49-211-6792-329, F: +49-211-6792-333, [email protected] Yiyi Yang, Michigan State University T.R. Bieler, Michigan State University
D. Raabe, Max-Planck-Institut für Eisenforschung
We present results on the single crystal plasticity of commercial purity (CP) titanium. Through EBSD orientation mapping a region with a high variability of crystallographic orientations was determined in annealed poly-crystalline titanium. Then a series of nanoindentation experiments was carried out in this region. Additionally, representative indents for several orientations were characterized for their surface topography by tapping mode AFM.
The anisotropic response of titanium during nanoindentation was analyzed through the combined evaluation of the nanoindentation data and the crystallographic orientations from EBSD. Strong hardness anisotropy was observed and the highest hardness was measured for indentation along the c-axis.
The experimental data on the orientation dependent surface pile-up were then processed through the method described by Zambaldi & Raabe [1] to generate the inverse pole figure of indentation pile-up topographies of alpha-titanium. For indentation into crystallographic directions away from the c-axis, pile-up occurred on both sides of the projection of the c-axis into the indented plane. This is in good agreement with the known prevalence of prismatic slip in titanium. Almost no surface pile-up was found for indentation in the vicinity of the c-axis orientation which is also the hardest direction.
The collected experimental data served as a reference for subsequent crystal plasticity finite element (CPFE) simulation of the indentation process. The pile-up together with the load-displacement curves were used to calibrate the parameters of the crystal plasticity constitutive model. The simulated surface topographies were in good agreement with the experimental data. The potential of the combination of EBSD, nanoindentation, AFM and CPFE for rapid quantification of single-crystal plasticity in structural alloys is demonstrated.
References [1] C. Zambaldi, D. Raabe, 2010, Acta Materialia 58( 9) 3516-3530
Tuesday, October 11, 2011 Indentation I
ELASTIC ANISOTROPY OF MATERIALS STUDIED BY NANOINDENTATION AND ATOMIC FORCE ACOUSTIC MICROSCOPY TECHNIQUES
Kong Boon Yeap, Fraunhofer Institute for Nondestructive Testing Maria-Reiche-Str. 2, Dresden, Saxony, 01109, Germany
Ude Hangen, Hysitron Incoporation Ehrenfried Zschech, Fraunhofer Institute for Nondestructive Testing
The elastic anisotropy of single crystals, e.g. Cu, Si, CaF2, and MgF2, is shown by nanoindentation at several-10nm and at sub-10nm deformations, and by atomic force acoustic microscopy (AFAM) at single 1nm deformation. To determine the materials elastic properties by applying small deformations, the accurate determination of the tip geometry is necessary for both nanoindentation and AFAM techniques. In this study, a tip calibration procedure based on the Hertzian model is used for the nanoindentation method at sub-10nm deformation. Such calibrated tip radius is used to determine the reduced moduli values from sub-10nm deformations in nanoindentation experiments. The obtained values are close to the theoretical uni-directional values obtained from the materials stiffness matrix. However, with increasing deformation depth to several-10nm, the reduced moduli gradually change from the uni-directional values to the Hill’s averaged values. AFAM modulus mapping of the imprint that remained after a nanoindentation measurement at several-10 nm depth shows that modulus of the area within the indent imprint is close to average values of the same polycrystalline material, while the values of the elastic modulus determined for the area outside of the imprint remains close to those of the uni-directional modulus. The transition of the reduced moduli from uni-directional values to averaged values occurs at different nanoindentation depths for different crystalline materials, due to indentation-induced (or stresses-induced) changes of the atomic order, e.g. phase transformation in Si and crystal lattice rotation in Cu. The values of the reduced modulus measured for the elastically anisotropic materials at several-10nm depths are resulted from the elastic properties of the structure with changed atomic order and the original crystal structure.
Tuesday, October 11, 2011 Indentation I
NEW METHOD BASED ON SECOND HARMONIC DETECTION TO EXTRACT MECHANICAL PROPERTIES FROM DYNAMIC NANOINDENTATION TESTS
Jean-Luc Loubet, Ecole Centrale de Lyon, Laboratoire de Tribologie et Dynamique des Systèmes, UMR 5513 CNRS/ECL/ENISE
36 Avenue Guy de Collongue, Ecully, 69134, France T: +33(0)4 72 18 62 81, F: +33(0)4 78 43 33 83, [email protected]
Gaylord Guillonneau, Ecole Centrale de Lyon, Laboratoire de Tribologie et Dynamique des Systèmes, UMR 5513 CNRS/ECL/ENISE, 69134 Ecully, France
Sandrine Bec, Ecole Centrale de Lyon, Laboratoire de Tribologie et Dynamique des Systèmes, UMR 5513 CNRS/ECL/ENISE, 69134 Ecully, France
Guillaume Kermouche, Ecole Nationale d’Ingénieurs de Saint-Etienne, Laboratoire de Tribologie et Dynamique des Systèmes, UMR 5513 CNRS/ECL/ENISE, 42000 Saint-Etienne, France
Extraction of mechanical properties of materials from nanoindentation tests needs determination of the projected contact area. Different formulas and procedures can be used to calculate this indentation surface from the displacement measurement. However, material properties are more difficult to obtain for small penetration depths, below 100nm. A new method based on second harmonic detection for dynamic nanoindentation testing is proposed. This technique permits to determine the Young modulus and the hardness of materials at small depths. With this new method, the measurement of the normal displacement is indirectly used, avoiding needing precise contact detection. Moreover, the tip defect and thermal drift influence on the measurements are reduced. This method was applied on silica and an amorphous polymer (PMMA). Results show that the amplitude of second harmonic can be correctly measured at small depths. The Young modulus and the hardness of the tested materials can be obtained from this measurement with rather good accuracy. The mechanical properties determined with this new method are in good agreement with values obtained with classical nanoindentation tests and extend their domain. Influence of indentation size effect at small penetration depths and the limitation of the technique are discussed.
Tuesday, October 11, 2011 Indentation I
MECHANICAL PROPERTIES MAPPING USING PROBE EXPERIMENTS: FACT AND FICTION
Warren C. Oliver, Nanomechanics Inc. 105 Meco Lane, Suite 100, Oak Ridge, TN, 37830, USA
The application of the CSM technique to the generation of stiffness maps will be discussed. A number of applications of this technique will be shown. A few years ago a technique was proposed to allow stiffness maps to be converted to modulus maps. The stringent experimental requirements associated with this conversion technique render it inaccurate, insensitive and virtually useless. New techniques for the generation of true mechanical properties maps in reasonable periods of time will be introduced and demonstrated. The technique involves performing individual indentations at each point in the map, but the speed at which the indentations are performed is increase by a factor of 1000 compared to normal nano indentation experiments. The resulting time per data point in the image (<0.5 sec) allows maps with reasonable resolution to be performed. Some of the advantages of this approach including minimized tip wear and improved measurement statistics will be discussed.
Tuesday, October 11, 2011 Indentation I
IN SITU, ELEVATED TEMPERATURE NANOINDENTATION: BEST PRACTICES AND CASE STUDIES
J.M. Wheeler, Mechanics of Materials and Nanostructures Laboratory EMPA - Materials Science & Technology
J. Michler, Mechanics of Materials and Nanostructures Laboratory EMPA - Materials Science & Technology
Nanoindentation at elevated temperature is an increasingly popular area of research [1-2] with a several custom systems at various institutions and variety of manufacturers offering standard options for elevated temperature testing. These encompass a range of technical solutions for performing tests: indenter/sample heating, water cooling, heat shields, inert gas shrouding, vacuum chambers, etc. These all attempt to circumvent the challenges of thermal displacement drift and indenter/sample oxidation. A brief summary of these technical solutions and how they address these challenges will be made, specifically with regards to the modifications made to an in situ nanoindentation system for testing at elevated temperatures up to 500°C within an SEM. Procedures for the calibration of the tip temperature via Raman spectroscopy and precision thermocouple measurements will be discussed, and the mechanisms of thermal drift will be discussed as revealed via careful thermometry.
A survey of candidate indenter materials for high temperature testing up to 1000°C will be presented with specific regard to their high temperature hardness and wear behaviour and their chemical reactivity with oxygen and specific classes of materials.
A wide variety of materials display interesting mechanical behaviour at elevated temperatures. By using an in situ SEM elevated temperature indenter, a unique ability of coupling observation and measurement of mechanical deformation has been achieved. In addition to standard reference materials such as fused silica, pure aluminium, and tungsten, several classes of materials have been investigated: bulk metallic glasses and silicon/III-V semiconductors.
Bulk metallic glasses exhibit unique combinations of structural and functional properties. Ex situ studies [3] have investigated the deformation mechanics and mechanisms of BMGs at temperatures close to and below the glass transition temperature. In situ investigation was utilised to simultaneously explore the relationship between the measured load-displacement curves and observed surface shear offset displacements as a function of temperature and to determine the transitions between serrated and smooth flow with strain rate and temperature. Further ex situ investigation was used to statistically characterise the transition.
It has been observed that silicon and III-V semiconductor materials undergo a brittle-ductile transition at elevated temperature. A brittle-ductile transition has also been observed in situ in silicon micro-pillars at room temperature with pillar diameters of less than ~350nm yielding in a ductile fashion [4]. In this work, the ductile-brittle transition and yield strength of silicon and III-V semiconductor micro-pillars has been determined as a function of temperature and length-scale.
References [1] NM Everitt et al. Phil. Mag. 91, 1221-1244(2011). [2] ZC Duan and AM Hodge. JOM, 61,32-36 (2009). [3] CA Schuh, AC Lund and TG Nieh. Acta Mater. 52, (20) 5879-5891 (2004). [4] F Oestlund et al. Adv. Funct. Mater.19, 2439–2444 (2009).
Tuesday, October 11, 2011 Indentation I
HOT MICROCOMPRESSION IN VACUUM UP TO 700˚C
S. Korte, University of Cambridge Pembroke St, Cambridge, CB2 3QZ, UK
T: +44 1223 334339, F: +44 1223 334567, [email protected] R.J. Stearn, University of Cambridge
S. Goodes, Micro Materials Ltd W.J. Clegg, University of Cambridge
For instrumented indentation to be a quantitative test technique, the loads and displacements must be accurately measured. However, at elevated temperatures there are two major problems: thermal drift and oxidation of both the indenter tip and sample surface. These are ideally avoided by testing in vacuum, but it has been shown that the lack of atmosphere can lead to increasing problems with heating of the equipment and equilibration at the tip-sample contact [1]. This paper describes an existing high temperature nanoindenter that has been modified for high temperature testing in vacuum. Using indentation of gold and microcompression of superalloy micropillars, it is shown that the modifications enable testing up to at least 700 °C in vacuum at low levels of both thermal drift and oxidation.
The thickness of the copper coatings that are used for the manufacture of conducting tracks in microelecronic devices are being aggressively scaled and there is a need to monitor the mechanical response of metallisation at a scale comparable to the material microstructure. When using indentation tests to assess the properties of thin films the plastic zone dimensions may be comparable to the grain size. For the purposes of design based on continuum mechanics approaches it is usually required that the grain size is very much smaller than the deforming volume which is not always observed in practice. Considerable differences between predicted and observed performance can be seen depending on the material tested and its grain size; the extent of oxidation of the copper after deposition is critical. Whereas it is possible to make good measurements of metallisation properties on stiff substrates such as silicon there are serious issues with the reliability of data from coatings on compliant substrates such as the PET used for plastic electronics. This presentation will highlight the effect of grain size, shape and orientation on the mechanical response of metallic thin films used for semiconductor metallisation on silicon and PET. The conditions under which continuum mechanics may be used successfully will be discussed and the effect of crystallographic anisotropy and oxidation on the choice of appropriate design data will be highlighted for copper coatings.
Tuesday, October 11, 2011 Indentation II
TWIN BOUNDARY MOTION IN MAX PHASE MATERIALS ACTIVATED BY NANOINDENTATION
C. Tromas, Institut P’, UPR 3346 CNRS – Université de Poitiers – ENSMA Département de Physique et Mécanique des Matériaux
Bât. SP2MI, Bd. Pierre et Marie Curie, BP 30179, Futuroscope Chasseneuil Cedex, 86962, France T: 0033549496724, F: 0033549496692, [email protected]
J. J. Roa Rovira, P. Villechaise, A. Guitton, L. Thilly, A. Joulain, Institut P’, UPR 3346 CNRS – Université de Poitiers – ENSMA Département de Physique et Mécanique des Matériaux
Due to its local deformation, complex stress field and nanometre scale control, the nanoindentation test is a very interesting method to study the elementary plastic deformation mechanisms in terms of individual dislocations. This technique has been used in this study to investigate the plasticity of the MAX-phase material Ti3AlC2. Mn+1AXn-phases (n=1, 2 or 3) materials are a class of nanolaminated ternary carbides or nitrides, with a hexagonal structure, where M stands for an early transition metal, A for a group A-element and X for carbon or nitrogen. MAX-phase materials present a unique combination of metal and ceramic properties. Their high technological potential is largely due to their specific mechanical properties, associating damage tolerance and easy machinability. Plastic deformation has been locally introduced by nanoindentation in individual grains of a Ti3AlC2 polycrystalline sample. The surface deformation and the slip lines around the indents have been observed by Atomic Force Microscopy (AFM). The local crystallographic orientations have been determined by Electron BackScattered diffraction (EBSD). In particular, EBSD observations have revealed pre-existing twin boundaries, which are likely to be produced during the cooling stage of the synthesis process. It has been observed that these twin boundaries are mobile in the indentation stress field, leading to changes of slope on the surface, which are characteristic of twinning or de-twinning mechanisms. Furthermore, the hardness mapping, obtained by large regular indentation arrays, clearly shows that these mobile twin boundaries are associated to low hardness values. Deformation twinning can be thus operative in MAX phase materials at room temperature and can increase locally their ductility.
Tuesday, October 11, 2011 Indentation II
NANOINDENTATION STRAIN-RATE JUMP AND LONG-TERM CREEP TESTS ON NANOCRYSTALLINE MATERIALS
Verena Maier, General Materials Properties, Department Materials Science and Engineering, University of Erlangen-Nuernberg
Benoit Merle, General Materials Properties, Department Materials Science and Engineering, University of Erlangen-Nuernberg
Mathias Göken, General Materials Properties, Department Materials Science and Engineering, University of Erlangen-Nuernberg
Karsten Durst, General Materials Properties, Department Materials Science and Engineering, University of Erlangen-Nuernberg
The time-dependent mechanical behavior and thus the strain-rate sensitivity is an important indication for thermal activated deformation processes. With conventional uniaxial macroscopic testing, these processes can only be studied on a macroscopic scale, averaging over many microstructural length scales and features. However, nanoindentation testing is a useful tool for studying these effects on the local scale.
Nanoindentation strain-rate jump tests were used to determine the strain-rate sensitivity at strain-rates between 10-2 s-1 to 10-4 s-1. The implementation of abrupt strain-rate jumps during a single indent leads to a minimization of thermal drift influences and a good agreement with macroscopic compression tests is achieved. Using long-term nanoindentation creep tests, the local time-dependent mechanical behavior at a considerably lower creep-rate can be examined. However, conventional nanoindentation creep tests are also strongly influenced by thermal drift. Therefore, a dynamic indentation method was used for continuously measuring the contact stiffness. Using Sneddon’s equation, the contact area and thus the instantaneous contact depth is determined continuously from the measured stiffness. This method allows nanoindentation creep experiments up to 24 hours without thermal drift influences. Accordingly, a creep-rate exponent can be assessed directly by plotting the creep rate versus the respective hardness.
Experiments were carried out on face-centered cubic nickel and aluminum with nanocrystalline (NC) and coarsened-grained (CG) structure. Generally, an enhanced strain rate sensitivity was found for NC-materials compared to the CG-material. However, creep testing led to a higher rate sensitivity than nanoindentation strain-rate jump tests, which is caused by a change in the deformation mechanism. Finally, the local time-dependent mechanical behavior was compared to macroscopic compression as well as to macroscopic stress controlled creep tests.
Tuesday, October 11, 2011 Indentation II
THE INTERPRETATION OF SPHERICAL INDENTATION THROUGH MULTISCALE MATERIAL MODELING: FROM POLYCRYSTALLINE TO SINGLE-CRYSTAL MICRO AND NANO-INDENTATIONS
J. Alcala, Universitat Politecnica de Catalunya Avda. Diagonal 647, Barcelona, 08028, Spain
T: +34 93 4016287, F: +34 93 4016706, [email protected] D. Esque-de los Ojos, Universitat Politecnica de Catalunya, Spain
R. Dalmau, Universitat Politecnica de Catalunya, Spain L. Galceran, Universitat Politecnica de Catalunya, Spain
J. Ocenasek, New Technologies Research Center, Czech Republic
The purpose of this presentation is to provide a self-consistent framework to the understanding of spherical indentation experiments from macro- to micro-scopic scales in crystalline materials. In doing so, we seek to examine the size effects that arise as the diameter of the spherical tip varies from millimeters to hundreds of micrometers to tens of nanometers. Indentation induced plastic flow is investigated through comprehensive continuum (non-local) plasticity and crystal plasticity finite element simulations, as well as through molecular dynamics simulations. The computational modeling is also confronted against detailed experimental measurements.
The first part of the presentation revisits the use of self-similarity schemes in the investigation of the spherical hardness evolution with increasing penetration in polycrystalline metals (i.e., indentations performed at macroscopic scales). A detailed assessment is given to the mechanics underlying transition from elasto-plastic to the fully-plastic indentations by focusing in such issues as the plastic flow patterns, the role of strain hardening or its absence, the meaning of large strains from the perspective of both the indenter shape and the plasticity theory, and similarities between fully-plastic sharp and spherical indentations. The results enable construction of a contact deformation map and a novel general hardness relation that allows accurate mechanical property extractions irrespectively of the active contact regime.
The second part of the presentation concerns extension of the above contact regimes to single crystal spherical indentations performed in pure and alloyed metals with different values of critical resolved shear stress for dislocation gliding. The meaning of mechanical property extractions from single crystal indentation measurements is also covered, where a parallel is drawn between such extractions and those resulting from the above polycrystalline indentations at macroscopic scales. For the first time, attention is directed to find specific crystallographic orientations in fcc crystals whose uniaxial response is probed through microindentation tests. This extends, the pioneering work by Tabor to single crystal microindentations.
The above background is finally used in the evaluation of material-related size effects, where a detailed micromechanical discussion is given on the distinctions between the incipient plasticity behavior probed in low-load nanoindentation (as in the present molecular dynamics simulations), and the plasticity arising in microindentation experiments that employ spherical tips in the millimeter range (where it is shown that continuum crystal plasticity can still be used to assess size dependent indentations). It is also our purpose to analyze the latter material size effects in the context of their influence in the transition from elasto-plastic to fully-plastic indentation regimes.
Tuesday, October 11, 2011 Indentation II
NANOINDENTATION BASED ASSESSMENT OF EFFECTIVE COMPOSITE PROPERTIES
J. Nìmeèek, Czech Technical University in Prague Thákurova 7, Prague 6, 16629, Czech Repubic
T: +420224354309, F: +420224310775, [email protected] V. Králík, Czech Technical University in Prague
J. Vondøejc, Czech Technical University in Prague J. Nìmeèková, Czech Technical University in Prague
The contribution deals with the assessment of effective (homogenized) elastic properties of several structural composites based on mechanical data received in nanoindentation tests.
Several structural materials, namely cement paste, gypsum and an aluminum alloy, are studied in details. They are typically characterized by a high degree of heterogeneity given by the mix of phases that can hardly be separated or produced independently on the others. Therefore, it is necessary to assess mechanical properties of individual phases in the composite. The phases occur typically in the scale around 1 micron. Their properties are found with the aid of nanoindentation. Small indentation depth (~100-300 nm) is used to access individual components of these natural composites. Since the natural scatter of the results even on one phase and also due to possible interaction of phases is high, it is necessary to use statistical approach in the evaluation of results. It includes massive array indentation and subsequent deconvolution procedure. In this method, experimental data are analyzed from the frequency plots of the given mechanical characteristics. Mean elastic properties of individual mechanically different phases as well as phase volume fraction are estimated.
Subsequently, several micromechanical up-scaling methods are utilized to find effective elastic properties of these materials. Analytical homogenization schemes (Hashin-Sthrikman bounds, Mori-Tanaka scheme) are compared with more advanced FFT-based homogenization method. Simple analytical schemes assume isotropy of the materials within representative volume which is not the case of a numerical scheme. As a result, effective stiffness matrices for the given materials are produced.
Based on the comparison of analytical and numerical schemes, it was concluded that a very good estimate is provided by analytical schemes for the studied materials which is due to the close-to-isotropic nature of their composition.
Tuesday, October 11, 2011 Indentation II
OBTAINING CRYSTAL PLASTICITY PARAMETERS BY INVERSE ANALYSIS OF NANOINDENTATION RESULTS
Benjamin Schmaling, ICAMS - Ruhr-Universität Bochum Stiepeler Str. 129-131, Bochum, NRW, 44801, Germany
We present a method to identify crystal plasticity parameters from nanoindentation tests based on an inverse procedure consisting of a finite element model (FEM) of nanoindentation and an efficient optimization algorithm. Experimental results obtained from nanoindentations on various iron alloys are presented. These nanoindentation and AFM measurements provide the necessary information to identify macroscopic power-law hardening material parameters of elastoplastic materials. Additionally, the crystal orientation relative to the indentation axis is measured by means of EBSD analysis and used for identification of single crystalline constitutive behavior. The experimental results were used to answer two essential questions: Firstly, can one identify macroscopic material parameters by depth-sensingindentation and the proposed inverse method if microstructuralcomponents are small compared to the indentation profile and depth.Secondly, if the microstructural components are large compared toindentation profile, i.e. indentation is carried out into a single phase for example,can one identify essential crystal plasticity parameters for yielding and hardening behavior. The commercial software Abaqus is used for the finite element modeling (FEM) and a dislocation-based crystal plasticity modelis implemented via the user subroutine UMAT. An optimization algorithm based on an effective metamodelling approach minimizes the mean square error between simulation and experiment with the benefit of a small number ofcomputationally expensive function calls, especially for the crystal plasticity FEM runs. Key factors for identifying material hardening behavior are identified and quantitative material parameters are presented. Results are compared to material parameters obtained by uniaxial testing and are discussed with respect to uniqueness of the identified parameters along with chances and limitations of the proposed method.
Wednesday, October 12, 2011 Deformation Mechanisms I
OBSERVATION OF DISLOCATION-MOVEMENT IN PASSIVATED AL FILM USING IN SITU TRANSMISSION ELECTRON MICROSCOPY NANOINDENTATION
Ludvig de Knoop, CEMES-CNRS 29 rue Jeanne Marvig, Toulouse, 31055, France
Understanding the mechanical properties of nanomaterials is a subject of major interest in different fields of nanosciences and nanotechnologies. Particularly in microelectronics, metallic thin films used in interconnections are subjected to high current density and consequently high thermal loads. Thermal loads generate stresses. Hence, stress-strain relations and elastic to plastic transitions becomes a critical issue to warrant device integrity.
With the advent of in situ transmission electron microscopy (TEM) nanoindentation, the mechanical behavior of small-scale samples can be investigated at the nanoscale, as plastic behavior can be triggered locally and the associated physical processes followed dynamically in the microscope.
Here, we investigate the plastic behavior of passivated Al thin films. A dedicated TEM sample holder, equipped with an actuator and a diamond mounted on a force-sensing MEMS device, allows indenting cross-sectional specimens fib-milled in a H-bar configuration. Al films of 1 μm thickness are deposited on a Si substrate and covered by a 1 μm thick SiO2 layer. To study the dislocation behavior at the Al/SiO2 interfaces, the upper layer of silica, which is designed to distribute the stress imposed by the indenter and also to function as a protective layer during the fib-milling process, is pressed into the diamond indenter.
Load-unload curves acquired in situ have shown that dislocations tend to move towards the Al/SiO2 interface. The result is compared with in situ thermal cycling of similar samples, where the stress originates from difference in thermal expansion coefficients. To support the discussions, finite element models are built to calculate the transmitted stresses into the Al film by the indentation process, as well as to estimate the thermal stresses in the heating experiments.
Wednesday, October 12, 2011 Deformation Mechanisms I
SIZE DEPENDENCE OF STRENGTH OF METALLIC MICROPILLARS AND THE PREREQUISITES FOR THE FORMATION OF STABLE PINNING POINTS
Seok-Woo Lee, Stanford University Department of Materials Science and Engineering, Stanford University, Stanford, CA, 94305-4034, USA
T: +1-650-799-1566, F: +1-650-725-4034, [email protected] William D. Nix, Stanford University
Recent micro-mechanical tests have shown that ‘Smaller is Stronger’ even in the absence of significant strain gradients, an effect that is usually characterized by a power-law approximation. While this power-law relationship between size and strength has been extensively used, its physical origin is still not fully understood. Here using Parthasarathy’s statistical concept, we present a simple and quantitative analysis that can be used to interpret the power-law exponents for micropillars a few micrometers in diameter. The different scaling exponents for different metals are understood by incorporating material parameters such as the friction stress, the anisotropic shear modulus, and the magnitude of Burgers vector into the analysis. Furthermore, by analyzing the factors that affect the strength of micropillars, we show a new form of the scaling law that holds for both FCC and BCC metals. Also, recent experimental studies of the effect of increasing the dislocation density, which show hardening for large micropillars and softening for small micropillars, are interpreted by considering the statistical distribution of dislocation pinning points.
Parthasarathy’s pinning point model can capture the yield strength in terms of the initial dislocation density, but cannot deal with the dynamics of pinning points, which is important to understand the evolution of dislocation structures at a small scale. Based on a simple geometrical analysis, especially for FCC crystals, we show that the insertion of jogged dislocations or the implementation of cross-slip during relaxation and subsequent plastic flow are prerequisites for the formation of strong natural pinning points and single arm dislocation sources. Absent these conditions, we argue that mobile dislocation starvation will occur naturally in the course of plastic flow and lead to a state in which plastic flow is controlled by the nucleation of dislocations, most likely at the free surfaces of the micro-pillar. The recent experimental and computational results will be critically assessed based on our geometrical analysis.
Wednesday, October 12, 2011 Deformation Mechanisms I
INITIAL DISLOCATION STRUCTURES AND BOUNDARY CONDITIONS IN 3D DISCRETE DISLOCATION DYNAMICS SIMULATIONS AND THEIR INFLUENCE ON MICRO SCALE PLASTICITY
Christian Motz, Erich Schmid Institute, Austrian Academy of Sciences Jahnstrasse 12, Leoben, Styria, A-8700, Austria
T: +43 3842 804 101, F: +43 3842 804 116, [email protected] J. Senger, IZBS, Karlsruher Institute of Technology (KIT)
D. Weygand, IZBS, Karlsruher Institute of Technology (KIT) P. Gumbsch, IZBS, Karlsruher Institute of Technology (KIT)
Size effects in mechanical properties are gaining more attraction in recent years induced by the ongoing miniaturization in many fields. Besides experimental work, also simulation tools are used to elucidate the underlying deformation mechanisms causing the observed size effect. Especially 3D discrete dislocation dynamics simulations are utilized to investigate this phenomena. As discrete dislocation dynamics describes the evolution of an existing dislocation structure with time, the choose of the initial structure is of great importance. Usually, Frank Read sources are used as starting dislocation structure. One disadvantage of this initial structure are the persistent pinning points that are introduced into the dislocation network, which avoid the study of mechanisms like dislocation starvation. To overcome this problem, realistic dislocation network topologies were generated by relaxing an initially pinning point free dislocation loop structure using 3D discrete dislocation dynamics simulations. Traction free finite sized samples were used. Subsequently, these equilibrated structures were subjected to tensile loading and their mechanical behavior was investigated with respect to the initial configuration. A strong mechanical size-effect was found. The flow stress at 0.2% plastic deformation scales with specimen size with an exponent between -0.6 and -0.9, depending on the initial structure and size regime. During relaxation, a mechanism, also favoured by cross-slip, is identified which leads to rather stable pinning points. These pinning points are comparable to those of the isolated Frank Read sources (FRS) often used as a starting configurations in previous discrete dislocation dynamics simulations. These nodes act as quite stable dislocation sources, which can be activated multiple times. The influence of this source-mechanism on the mechanical properties of small scale specimens is discussed.
Wednesday, October 12, 2011 Deformation Mechanisms I
A SIMPLE STOCHASTIC MODEL FOR YIELDING IN SPECIMENS WITH A LIMITED NUMBER OF DISLOCATIONS
George M. Pharr, University of Tennessee and Oak Ridge National Laboratory Dept of Materials Science and Engineering, 434 Dougherty Engineering Building, Knoxville, TN, 37996-
P. Sudharshan Phani, University of Tennessee Kurt E. Johanns, University of Tennessee
Easo P. George, University of Tennessee and Oak Ridge National Laboratory
A simple stochastic model based on a random distribution and orientation of dislocations is developed to explain recent experimental observations of enhanced strength in small specimens containing a limited number of dislocations. Two different types of randomness are introduced, viz., randomness in the location of dislocations and randomness in the stress needed to activate them. For convenience, the randomness in the activation stress is modeled by assigning a random Schmid factor, while the randomness in location is treated by a simple probabilistic model and verified with Monte Carlo simulations. In contrast to the previous stochastic models, the current model predicts not only the yield strength in the presence of dislocations but also in their absence. Furthermore, the model has the capability to quantitatively predict the scatter in the yield strength and how it varies with specimen size. The model is tested by comparing its predictions to recent experimental observations of the yield strengths of sub-micron diameter Mo alloy fibers measured in tension and compression tests. The predictions are based on dislocation densities and arrangements measured independently by transmission electron microscopy. The model can be extended to explain the dependence of nanoindentation pop-in stresses on indenter radius.
This work was supported by the Center for Defect Physics, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.
Wednesday, October 12, 2011 Deformation Mechanisms I
INFLUENCE OF BULK PRE-STRAINING ON THE SIZE EFFECT IN NICKEL COMPRESSION PILLARS
Andreas Schneider, INM-Leibniz-Institut für Neue Materialien Campus D2 2, Saarbrücken, 66123, Germany
T: +496819300312, F: +496819300279, [email protected] Daniel Kiener, University of Leoben, Department of Materials Physics, Jahnstr. 12, 8700 Leoben, Austria Patric Gruber, Karlsruhe Institute of Technology, Institut für Zuverlässigkeit von Bauteilen und Systemen,
Kaiserstr. 12, 76131 Karlsruhe, Germany Hans Maier, Universität Paderborn, Lehrstuhl für Werkstoffkunde, 33098 Paderborn, Germany
Carl Frick, University of Wyoming, Mechanical Engineering Department, 1000 East University Avenue, Laramie, WY 82071, USA
Microcompression tests were performed on pre-strained nickel (Ni) single crystals in order to investigate the influence of the initial dislocation structure on the size dependence of small-scale metal structures. A bulk Ni sample was grown using the Czochralski method and sectioned into four compression samples which were pre-strained to nominal strains of 5, 10, 15 and 20%. Bulk samples were then characterized using transmission electron microscopy and electron backscatter diffraction. Results demonstrate that samples had a dislocation cell structure and that the crystallographic orientation had rotated significantly as a function of deformation magnitude. Pillars with diameters of 200 nm to 5 µm were focused ion beam microscope (FIB) machined from each of the four deformed samples and further compressed via a nanoindenter equipped with a flat punch. Results show that bulk pre-straining inhibits the size effect. Pillars in the micron range cut from heavily pre-strained bulk samples show elevated strength values; however, deformation history does not play a role in stress-strain behavior as diameter decreases below 1 μm.
Wednesday, October 12, 2011 Deformation Mechanisms I
EMERGENCE OF STRAIN RATE SENSITIVITY IN CU NANO-PILLARS: TRANSITION FROM DISLOCATION MULTIPLICATION TO DISLOCATION NUCLEATION
Andrew T. Jennings, California Institute of Technology 1200 E California Blvd. MC 309-81, Pasadena, CA, 91125, United States
T: 626-395-4416, F: 626-395-8868, [email protected] Christopher R. Weinberger, Sandia National Laboratory
Ju Li, University of Pennsylvania Julia R. Greer, California Institute of Technology
We demonstrate strain rate sensitivity emerging in single crystalline Cu nano-pillars with diameters ranging from 75nm up to 500nm through uniaxial deformation experiments performed at different constant strain rates. In the range of pillar diameters and strain rates tested, we find that the size dependence of the pillar strength deviates from the ubiquitously observed power-law, σ α D-n, to a relatively size independent flow strength, markedly below the predicted theoretical strength for strain rates slower than 10-1 s-1. We find this transition diameter, Dt, to be a function of strain rate, where faster strain rates shift the transition diameter to smaller pillar diameters. For instance at strain rates of 10-3 s-1 the Dt is ~150nm, while at faster strain rates, 10-1 s-1, the Dtis less smaller than 75nm. We compute the activation volumes, as a function of pillar diameter at each strain rate and find that for pillar diameters below Dt, the activation volumes are relatively small, less than 10b3 . This magnitude agrees favorably with atomistic simulations for dislocation nucleation from a free surface . We postulate a plasticity mechanism transition from dislocation multiplication via the operation of truncated dislocation sources, also referred to as single-arm sources, in pillars with diameters greater than Dt to dislocation nucleation from the surface in the smaller samples. Furthermore, we demonstrate an analytical framework to model surface sources and comment on factors that may influence their nucleation.
Wednesday, October 12, 2011 Deformation Mechanisms I
EXPLOITING INTERACTIONS BETWEEN INDENTATION SIZE AND STRUCTURE SIZE EFFECTS TO DETERMINE THE CHARACTERISTIC DIMENSION OF NANO-STRUCTURED
MATERIALS BY INDENTATION
Nigel M. Jennett, National Physical Laboratory Hampton Road, Teddington, Middlesex, TW11 0LW, UK
Enhanced yield (or flow) stress of materials has been linked to indentation size or structure size (e.g. some critical dimension such as grain size or pillar diameter) or both. Strength enhancement is generally proportional to an inverse square root of dimension, as in the Hall-Petch (H-P) effect.
Previously we showed that the uniaxial, compressive, yield strength (proportional limit) of tungsten single crystal monolithic structures exhibited a “thinness effect” (Jennett et al. 2009 Applied Phys. Lett. 95:123102). Wall-like structures (thin in a single lateral dimension) exhibit the same proportional limit as pillars of the same width, (but in both lateral dimensions). The material-independent scaling of the indentation size effect (ISE) when indenting metal single crystals (Spary et al. 2006 Phil. Mag. 86:5581-5593) suggests a geometric effect. We have also shown that, when indenting Cu poly-crystals, structure size effects and indentation size effects combine as a reciprocal sum of both critical dimensions; a further H-P like hardening is seen when grain size falls (from effectively infinite size) to less than six times the contact radius. (Hou et al. 2008 J. Phys. D: Applied Physics 41(7):074006).
In this paper we continue to evaluate evidence for a slip-distance based plasticity size effect mechanism in materials with multiple length scales. We study indentation flow stress as a function of indentation size in nano-structured materials. We indent 6 film thicknesses (100nm < t < 3000 nm) of nanocrystalline W (grain size < 10 nm) deposited on polished basal plane (0001) sapphire substrates. We show that indentation size and structure size have equivalent but separate effects on indentation flow stress and that the onset of ISE occurs at indentation sizes much greater than the grain size. This suggests that indentation may be used to determine the critical length scale of nanostructures. We test this idea by indenting two different metallic glasses (NiAl and ZrTiAlCuBe) and comparing results with careful TEM determinations of structure size. We find that the indentation depth at onset of ISE is proportional to the characteristic structure-size of these nano-structured materials.
Thursday, October 13, 2011 Deformation Mechanisms II
3DXRD allows non-destructive in-situ investgations of local microstructural changes in the bulk during mechnical and thermal loading. In the presantation the 3DXRD method is shortly described and the experimetal possiblities at varios instruments at ESRF and at APS are discussed. The potentials and the limitations of the 3DXRD method are illustrated by 4 types of experimental investigations: 1) lattice rotations within individual grains during tensile deformation. The results are compared to predictions by crystal plasticity models. As an overall result, the grain orientation is identified as the primary parameter controlling the slip sytems. 2) evolution of the dislocation structures within individual grains during tensile deformation. Almost dislocation free subgrains are identified and are observed to form already at about 0.1% strain. As the tests are in-situ uninterrupted tests, it is thus proven that such subgrains form during deformation and is not caused by any relaxation phenomenon. 3) development of grain resolved elastic strains during tensile deformation. The full strain tensors can be determined and the results show a clear grain orientation dependence with grains within 20deg of <100> carry the largest strain. 4) evolution of a recrystallized stucture upon thermal annealing. The formation and growth of nuclei in a deformed microstructure is followed in-situ. The results show very large local variations and that simple growth laws can not describe the local phenomena.
The experimental limitations discussed above for the 4 types of investigations have stimulated new plans for further development of the 3DXRD method and in the final part of the presentation these plans are shortly described.
Thursday, October 13, 2011 Deformation Mechanisms II
EXPECTED AND UNEXPECTED PLASTIC BEHAVIOR AT THE MICRON SCALE: AN IN SITU LAUE STUDY
Christoph Kirchlechner, University of Leoben Jahnstraße 12, Leoben, 8700, Austria
T: 03842 804 301, F: 03842 804 116, [email protected] Peter J. Imrich, Wolfgang Grosinger, Marlene W. Kapp, Erich Schmid Institut, Austrian Academy of
Sciences, Leoben Austria Jozef Keckes, University of Leoben, Leoben, Austria
Jean Sebastien Micha, Olivier Ulrich, CEA- Grenoble and CRG-IF BM32 at ESRF Gerhard Dehm, Erich Schmid Institut, Austrian Academy of Sciences, Leoben Austria
Plastic properties of single crystalline materials are size dependent, a circumstance which has been proofed by several studies during the last decade. Nevertheless, a thorough understanding is still lacking. This is partly caused by the limited number of appropriate in situ tools, which allow for interlinking the mechanical response with the corresponding dislocation structure. µLaue diffraction is able to provide the type and density of excess dislocations in micron sized samples and is well suited for the in situ characterization of the excess dislocation structure at the micron scale.
We have performed in situ tensile and compression experiments while collecting µLaue diffraction patterns at the European Synchrotron Radiation Facility (ESRF). The micron sized, focused ion beam (FIB) milled copper samples are single crystalline and oriented for single slip. By tracking the diffraction peak position and analyzing the diffraction peak shape, the rotation of the sample center as well as the type and density of excess dislocation has been investigated and interlinked to the simultaneously recorded force-displacement data.
The tensile experiments show two characteristic behaviors: (i) Slip without any storage of excess dislocations and (ii) a pile up of excess dislocations at low strains, which dissolves continuously during further straining or within a load drop. The post mortem investigations of the entire sample reveal an excess dislocation free sample center and huge peak streaking (strain gradients) near to the sample ends. The results of the tensile experiments will be discussed and compared to compression tests.
Thursday, October 13, 2011 Deformation Mechanisms II
PROBING STRAIN HARDENING BEHAVIOR IN MULTILAYER NANOLAMINATE SYSTEMS
David Bahr, Washington State University PO Box 642920, Pullman, WA, 99164-2920, USA
T: 509-335-8523, F: 509-335-4662, [email protected] Rachel Schoeppner, Washington State University Ioannis Mastorakos, Washington State University
Hussein Zbib, Washington State University
Nanolaminates, particularly metallic composites such as Cu/Nb, Cu/Ni, and Cu/Ni/Nb combinations, have been shown to have yield strengths that substantially surpass their monolithic components. This is due to the complex interactions of dislocations with the interfaces in the systems. However, the systems have traditionally exhibited limited ductility. Recent experimental tests of tri-layer systems have suggested these materials have greater strain hardening exponents than bi-layer systems, and complementary modeling efforts have suggested that this is due to the high stresses that can be achieved in the fcc layers in conjunction with the elastic modulus differences, which leads to cross slip and additional dislocation interactions in the tri-layer that are precluded from occurring in the bi-layer films. To further probe this behavior, three complimentary experiments were performed on a series of FCC/FCC/BCC tri-layer films (primarily Cu/Ni/Nb and Au/Cu/Mo). First, nanoindentation was performed using indenter tips of varying acuity, between Berkovich and cube corner geometries. The hardnesses and the out of plane deformation was assessed and correlated to the classical Tabor strain relationship with included indenter angle. These results are compared to micro-tensile testing on micromachined specimens where the sample geometry was formed using standard photolithographic techniques. Finally, the result of strain rate will be explained by examining films which have been subjected to a laser shock experiment and subsequently recovered with nanoindenation and the respective strains correlated to the quasi-static indentation and tensile test performance. The results will be presented in light of molecular dynamics and dislocation dynamics simulations of similar structures.
Thursday, October 13, 2011 Deformation Mechanisms II
TESTING OF ULTRA-SENSITIVE MATERIALS FOR NANO-ELECTROMECHANICAL SYSTEM - USENEMS
Peter Schaaf, TU Ilmenau Institute of Micro- and Nanotechnology, Gustav-Kirchhoff-Str. 5, Ilmenau, 98693, GERMANY
T: +49 3677 693611, F: +49 3677 693171, [email protected] Jörg Pezoldt, TU Ilmenau, Institute of Micro- and Nanotechnologies
Steffen Michael, IMMS Ilmenau Rolf Grieseler, TU Ilmenau, Institute of Micro- and Nanotechnologies Katja Tonisch, TU Ilmenau, Institute of Micro- and Nanotechnologies
An attempt for non-destructive determination of mechanical properties of new materials will be presented. The method could be used for the development of new ultra-sensitive materials in MEMS/NEMS structures, so that new sensors could be developed. Nanobeams and other structures of thin films are prepared for this purpose. Their intrinsic stress and their mechanical properties are tested by XRD and nanoindentation. At the same time they are tested by an optical vibrometer and the results are compared experimentally and by simulations. Result on AlN, MAX-Phase and grapheme films will be presented
Thursday, October 13, 2011 Deformation Mechanisms II
YIELD AND BUCKLING IN NANOWIRE ARRAYS
Matthias Schamel, Laboratory for Nanometallurgy, Department of Materials, ETH Zurich Wolfgang-Pauli-Strasse 10, Zuerich, 8093, Switzerland
T: 0041332284005, F: 0041332284490, [email protected] Jamil Elias, EMPA, Laboratory for Mechanics of Materials and Nanostructures, Thun, Switzerland
Laetitia Philippe, EMPA, Laboratory for Mechanics of Materials and Nanostructures, Thun, Switzerland Ralph Spolenak, Laboratory for Nanometallurgy, Department of Materials, ETH Zurich
Johann Michler, EMPA, Laboratory for Mechanics of Materials and Nanostructures, Thun, Switzerland
There is a need for synthesis techniques which provide tunable microstructure within a taper-less specimen, without an undesired influence from the fabrication process. Further on, mechanical testing on individual samples on the micro/nano scale is subject to statistical scatter due to the finite likeness between each specimen. Consequently, techniques with high throughput or simultaneous tests are highly desired.
In this study, the simultaneous compression of ordered arrays of nanowires allowed a reproducible evaluation of a compression experiment without the influence of single statistical events. Gold nanowires with diameters between 30 and 300 nm were produced by electrodeposition into ordered nanopores of anodic aluminum oxide membranes. Aspect ratio and microstructure were tuned depending on deposition parameters, pore size and polishing/etching steps. An approximate grain size of 50 nm was obtained, which lead to polycrystalline structure in the case of thicker wires (300 nm) and a segmented structure for thinner wires (30 nm). Electron backscattered diffraction on cross-sections and side surfaces as well as TEM analysis revealed additional twin boundaries in all cases.
While ex-situ indentation experiments monitored the collapse of such structures at distinct stresses, in-situ SEM compression allowed, for the first time, a direct distinction between buckling and compression response of nanowire arrays, which depends on aspect ratio and geometry. In the case of an aspect ratio of 8:1, buckling collapse towards open surfaces at stresses of 200 MPa for 300 nm wires was observed by SEM video analysis. Modeling of the buckling behavior revealed that an increase in failure stress is realized by reduction of aspect ratio or by lateral confinement of the individual nanowires, which would require deformation in higher order buckling modes. As a result, uniaxial yielding was achieved as the favored deformation mechanism at increased stresses for lower aspect ratios and high density of nanowires. Thus, a systematic study of the size dependence of the mechanical properties is enabled and will be presented in this contribution.
Thursday, October 13, 2011 Deformation Mechanisms II
FRACTURE TOUGHNESS OF MICRON-SIZED NIAL SINGLE CRYSTALLINE CANTILEVERS
T: 0049(0)91318527505, F: 0049(0)91318527504, [email protected] F. Igbal, J. Ast,
M. Goeken,
In recent years nanomechanical testing of materials became an important tool to understand the mechanical behaviour at the micron or even sub-micron scale. In-situ bending of Focused Ion Beam milled micro-cantilevers allows testing of i.e. interfaces or grain boundaries in polycrystalline materials. However, it is not clear how the small sample dimensions influence the local fracture properties of the material and if conventional linear elastic fracture mechanics concepts are still applicable at the micron scale. In order to understand the relation between microscopic and macroscopic fracture toughness of bulk materials, we carried out in-situ bending tests on notched NiAl-single crystalline cantilevers. The beams were prepared by Focused-Ion-Beam (FIB) machining and had approximate dimensions of 8 µm in length, 1.5 µm in thickness and 1.8 µm in width, with a notch tip radius ranging from 70 nm – 100 nm. An AFM-based force measurement system mounted inside a Scanning Electron Microscope (SEM) was used for loading the cantilevers until fracture and the fracture toughness of the soft <101> and the hard <100> orientation of NiAl was determined. We find a good agreement between microscopic and macroscopic fracture toughness values ranging from 3-4 MPa m1/2 for the soft and from 5-7 MPa m1/2 for the hard orientation. Limited crack tip plasticity is observed for the cantilevers, even though the macroscopic flow stress of the sample suggests a rather large plastic zone size. For estimating the local flow stress at the crack tip and stresses required for initiating plasticity, it is proposed to use the stress levels measured from nanoindentation experiments. Strain gradient at the crack tip increase the local flow stress, causing failure in a brittle fashion. Hence it is suggested that materials which show strong indentation size effects should yield a fracture toughness comparable to macroscopic fracture tests.
Thursday, October 13, 2011 Deformation Mechanisms II
EFFECT OF ION IRRADIATION ON THE MICROPILLAR COMPRESSION OF LIF SINGLE CRYSTALS
Jon M. Molina-Aldareguia, IMDEA Materials Institute c/Profesor Aranguren s/n, MADRID, 28040, Spain
T: +34 91 549 34 22, F: +34 91 550 30 47, [email protected] Rafael Soler, IMDEA Materials Institute
Javier Segurado, IMDEA Materials Institute and Departamento de Ciencia de Materiales, Universidad Politécnica de Madrid, E. T. S. de Ingenieros de Caminos
Victor Orera, Instituto de Ciencia de Materiales de Aragón C.S.I.C.-University of Zaragoza Javier Llorca, IMDEA Materials Institute and Departamento de Ciencia de Materiales, Universidad
Politécnica de Madrid, E. T. S. de Ingenieros de Caminos
Previous work by Uchic and co-workers (see Phil Mag A90, 3621–3649, 2010) has shown that size effects are not confined to metals but are also typical for solids of different classes, such as for instance, compounds like LiF. However, in their work the LiF micropillars were fabricated by FIB milling and a possible explanation for the size effects and flow stresses encountered might come from the initial surface defects introduced during FIB milling by the high-energy Ga ions. In this work, we have carried out compression of LiF micropillar single-crystals using a completely different approach to fabricate the micropillars, based on the pioneering work of Bei et al (Scripta Materialia 57, 397–400, 2007) for other material systems like Mo. In our case, single-crystal micro-pillars of LiF have been prepared by chemically etching away the matrix of directionally solidified NaCl–LiF and/or KCl-LiF eutectics. The size of the fibers was related to the eutectic growth rate and in this way, micropillars with diameters ranging between 1.5 and 5 micrometers could be produced without the need of using FIB milling. These pillars were then exposed to the ion beam inside a focused ion beam workstation. Compression tests have been performed using a nanoindentation system to obtain the yield and flow stresses as a function of ion beam irradiation, showing a different behavior. The differences between the pristine and ion irradiated micropillars will be discussed.
Thursday, October 13, 2011 New Instrumentations and Developments
MEASURING SUBSTRATE-INDEPENDENT ELASTIC MODULUS OF STIFF AND COMPLIANT FILMS BY NANOINDENTATION
Jennifer L. Hay, Agilent Technologies
105 Meco Lane, Suite 200, Oak Ridge, TN, 37980, USA T: 865-230-2328, F: 480-756-5950, [email protected]
Dr. Holger Pfaff, Agilent Technologies Campus Kronberg 7, Kronberg/Ts, HE 61476;GERMANY
Substrate influence is a common problem when using instrumented indentation (also known as nanoindentation) to evaluate the elastic modulus of thin films. Many have proposed models in order to be able to extract the film modulus (Ef) from the measured substrate-affected modulus, assuming that the film thickness (t) and substrate modulus (Es) are known. But until recently, no analytic model adequately predicted the response of stiff films on compliant substrates. In this work, a new analytic model is presented. By finite-element analysis, this new model is shown to accurately return the input film modulus over the domain 0.1 < Ef/Es < 10. Further, the model is shown to yield more accurate and meaningful results than extrapolating to zero penetration. Finally, the model is employed to interpret experimental nanoindentation results from a variety of film-substrate systems.
Thursday, October 13, 2011 New Instrumentations and Developments
COMPACT TEST PLATFORM FOR IN-SITU MATERIALS CHARACTERIZATION IN VARIOUS FIELDS OF MICROSCOPY
Materials characterization is a field that is constantly being pushed to contribute more to the development of materials for micro/nano components. In order to gain a fundamental understanding of the material properties at micro- and nano-scales, like failures or its non-conformities, there is an increasing demand to have the possibility to observe the material’s microscopic behavior during testing or during some typical operations as cutting, cleaving, stretching, bending, etc.
In-situ materials tests have the advantage of linking visual and sensor-based information during a dynamic experiment. The possibility to observe locally what is happening provides additional support for standard sensor-based measurements and consequently a more accurate interpretation of the results.
A compact mechanical testing platform has been developed to enable materials characterization beyond standard tests by combining an in-situ indenter with different kinds of microscopes to have complementary results, for example nanoindentation and scanning electron microscopy or micro-compression tests and Raman microscopy. This has the advantage of correlating microscope images and videos with the information output of the load x displacement graph.
Typical applications of the in-situ indenter are coating analyses (delamination, cracks), fracture studies (fracture toughness), bulk material studies, precise testing of a specific area (for example interfaces between two materials), and micro-compression to name but a few. In recent studies in-situ indentation as well as compression and bending of micropillars and microbeams have been used to analyse the mechanical behaviour of various materials such as bulk metallic glasses, silicon, GaAs, InP, TiN/SiNx coatings and wood.
Thursday, October 13, 2011 New Instrumentations and Developments
RECENT APPLICATIONS OF NANOINDENTATION MEASUREMENTS AND EVOLUTIONS OF INSTRUMENTATION
Philippe Kempe, CSM Instruments SA Rue de la Gare 4, CH-2034 Peseux, Switzerland
Nanoindentation has become an indispensable method for measuring mechanical properties of thin films or small volumes of materials. Though being developed for more than twenty years, contemporary methods used for nanoindentation are suffering several drawbacks:
- thermal drift of instrumentation, which limits the measurements of creep properties;
- analysis mostly limited to elasto-plastic materials;
- difficult determination of the contact point on soft materials.
The present paper introduces a novel ultra nanoindentation method that applies very low loads (from less than 1 μN up to 50 mN) and is capable to perform long-term measurements. The method is based on a patented design using active top referencing system and components made from Zerodur® glass to dramatically reduce the thermal expansion of the instrument frame.
Several materials including fused silica and DLC were able to demonstrate the very high resolution of this nanoindentation head. Tests were performed mainly at low loads to display the load and displacement resolution capabilities of the instrument. The method is then applied to thin films in order to better understand mechanical deformation of these materials under small deformation.
Measurements with a hold at maximum load confirmed the extremely low level of instrument thermal drift. This ultra nanoindentation method opens new possibilities of long-term testing for creep determination and polymer evaluation. The application of this instrumentation to extremely soft materials is also interesting as it can be used to determine mechanical properties of soft gels. Nevertheless, the additional physical phenomenon of adhesion is observed and the analysis of mechanical properties is then more complex.
Temperature testing is also in constant demand and the recent evolution of instrumentation in this matter is discussed.
Thursday, October 13, 2011 New Instrumentations and Developments
INNOVATIONS FOR MECHANICAL TESTING AT NANOSCALE
Ude D. Hangen, Hysitron, INC. Valley View Road 10025, Minneapolis, MN, 55344, USA
Hysitron´s innovations in transducer design and Performech controller technology have enabled key developments towards highly sensitive nanoindentation equipment. The combination of a measurement head with low inertia and a very fast controller allows the study of the origin of plasticity and strength of materials both in ambient conditions and in the electron microscope.
This presentation highlights some of our hybrid measurement techniques and reports the progress in measurement modes that are relevant to the most active fields of nanomechanical testing. Recent advances in dynamic testing modes, concurrent electrical measurements (nanoECR) and at different environmental conditions will be presented.
Thursday, October 13, 2011 New Instrumentations and Developments
A SIMPLE NEW METHOD TO MEASURE FORCE DISPLACEMENT CURVES
A simple approach to measuring nano and micro scale forces inside the SEM is the use of a spring table. A sample is mounted to a spring table and subsequently deflected, deformed or indented using a tool mounted to the tip of a micromanipulator. A sequence of images is recorded during the experiment. These images are processed with a custom software which utilizes image recognition, yielding force distance curves derived from the displacements measured in the SEM images and the well known force constant of the spring table.
High temperature indentation has, during the last years, been investigated in an attempt to better characterize the behavior of materials dedicated to high temperature applications in their working environment. It is now recognized that creating a stable thermal environment around both sample and indenter tip by independently heating them is critical for proper indentation measurement. Yet, thermal drift, e.g. thermal stability of the instrument, remains an issue demanding additional attention. Since thermo-mechanical properties are being measured it is expected that the sample behavior will demonstrate time dependency
This time dependency questions the validity of classic thermal drift correction methods, such as hold segment or multiple load-unload cycles, which are both valid in specific time independent cases. In such conditions, non-displacement based measurements are required to measure the stability of the instrument, prior and during the experiment. We have investigated the thermal processes undergoing in the instrument during the heating phase up to the stabilization phase and established a simple mathematical model providing for a practical measure for the instrument’s thermal stability that can be used to indicate when the instrument is ready to perform the indentation test, and indirectly estimate how thermal variations could affect the data during the experiment. We propose a solution based on both temperature and thermal flow management which provides better control of the instrument thermal stability
Thursday, October 13, 2011 New Instrumentations and Developments
TIP RADII EFFECTS ON THE FAILURE PRODUCED IN ULTRA-THIN FILMS BY SCRATCH TESTING
Bryan Crawford, Nanomechanics, Inc. 105 Meco Lane, Oak Ridge, Tennessee, 37830, USA
Scratch testing on ultra-thin films has been fraught with irreproducibility. The purpose of this study was to identify relationships between failure and tip radius during scratch testing of ultra-thin films. Using tip radii ranging from 50nm to 1µm, 350 nm thick low-k films on silicon have been tested showing the evolution of failure caused by a ramp-load scratch test as a function of tip radius. The data show that failure is highly dependent on the tip radius. Different types of failure dominate the response for different tip radii. On the extreme ends, sharp tips cause severe plastic deformation and cracking in the film - the film cracking is so severe that often it obscures failure at the interface between the film and substrate. Larger tip radii cause more elastic deformation in the initial stages of the scratch and allow higher levels of stress to propagate to the interface between the film and substrate prior to complete film failure. Failure from the larger tip radii is dominated by interface separation or large scale lateral fracturing.
All of the tests have been performed on a nanoindenter system that is equipped with scratch testing capabilities. Tip radii were varied on cube-corner shaped diamond tips and a three step ramp-load scratch process was used to perform the tests which included an original surface topography scan, the ramp-load scratch test, and a residual deformation scan. The three step scratch process allowed clear identification of the failure point. Identification of failure and techniques used to automatically detect film failure from the scratch curves will be discussed.
Finally, results from a process developed to generate tips with well controlled tip radii will be presented. These data show that tip-to-tip variation in the critical load can be controlled to within 5%. Even more, the reproducible tip radii can be used to optimize failure mechanisms in the material to closely mimic the failures seen in application. Tips can be optimized to produce failure that is concentrated in the film or at the interface by varying the tip radii. Results on low-k materials show that the tips can be made to provide minor failure in the films followed by interface separation and total film failure. This reproducibility in tip geometry provides a foundation for the production of scratch methodologies with confidence that long term repeatability is available.
Thursday, October 13, 2011 New Instrumentations and Developments
NANOMECHANICAL TESTING AT HIGH TEMPERATURES NEW SOLUTIONS FOR MORE ACCURACY
The indentation of small scaled samples with an indentation depth in the nm-range using µN forces is now a common technique. There are various approaches and manufacturer available on the market. There is always the need to measure and to minimize apparent thermal drift of the mechanical setup to get accurate results. This is an important aspect even at “room tem-perature”. For many applications there is a need to measure samples at higher temperatures to get meaningful results especially for high temperature application materials. There is a gene-ral trend in the community to develop models and apparatuses to serve this demand. SURFACE is a supplier for nanoindentation tools since 1996, but the company is also a well known manufacturer of complex vacuum deposition systems with even longer experiences, so our background was enable us to develop a precise heating technique far away from the normal. Our laser heating technique- developed for our deposition system to treat samples up to temperatures of 1000°C and above- was adapted to the nanoindentation process. The know-ledge of both fields has formed a user friendly high precise tool to meet the accuracy known from room temperature measurements. Based on an Agilent G200 nanoindentation setup we have developed a sample heater which allows users to measure in a temperature range up to 800 K. To minimize thermal drift due to the heating of the measuring setup and due to ther-mal variations we use a laser-based heating system which is controlled by a fast and accurate PID feedback loop. The short delay time of the laser heater enables us to stabilize the tempe-rature with a precision of approx. 0.05 K. Diamond tips are very good thermal conductors, so when tip and sample are brought into contact at different temperatures a temperature gradient on the sample will occur. Due to this flux the temperature of the tested volume under the tip is different from the set value of the bulk and remarkable thermal drift can influence the results negatively. In a recent publication by Everitt et al these effects are studied in detail [1]. For our Laser heating system we also offer a heater option for the tip. The tip is equipped with an additional laser and an independent controller setup. The combination of stage and tip heater enables very low drift rates close to the displacement noise of a room temperature contact. The measurement under ambient conditions sets of course limits in the temperature, but the combination with a vacuum set-up extend this to the full temperature range of each material. The different experiments of setting an ambient nanoindenter into a big vacuum chamber can’t be a solution, because it generates in the same time new limits. Such set-up is also effected from a very long stabilization time even at rel. low temperatures. Going to higher temperatures needs a new kind of system and new solutions to meet the necessary sensitivity and accuracy. Laser heating as a tool for nanomechanical testing is not limited only to nanoindentation. The advantages of the minimized and only on the sample size oriented heated area in a mechanical test system is always an advantage. That was the reason, that SURFAFCE has introduced the laser heating for SEM and TEM systems. Heating, focused to small structures is available now and can be positioned with a high precision 3D piezzo manipulator at a sample stage of an SEM. The heating spot size is variable from 0,2 mm up to several mm in diameter and can be adapted insitu to the substrate structures. [1] N.M. Everitt, M.I. Davies, and J.F. Smith: High temperature nanoindentation - the importance of isothermal contact. Phil. Mag. 91, 1221-1244 (2011)
Friday, October 14, 2011 “Novel” Materials
A COMBINATORIAL APPROACH USING NANO SCANNING CALORIMETRY AND X-RAY DIFFRACTION TO STUDY THE EFFECT OF COMPOSITION AND QUENCH RATE ON THE
CRYSTALLIZATION OF AU-SI-CU METALLIC GLASSES DURING RAPID HEATING
Joost J. Vlassak, Harvard University 29 Oxford Street, Cambridge, MA, 02420, USA
T: (617) 496 0424, F: (617) 496 0424, [email protected] John M. Gregoire, Harvard University
Patrick J. McCluskey, Harvard University Shiyan Ding, Jan Schroers, Yale University
Darren S. Dale, Cornell University
Calorimetric studies of bulk metallic glasses are typically performed at heating or cooling rates smaller than about 102 K/s, because of experimental limitations associated with bulk calorimeters. While faster cooling rates can be attained in uncontrolled quench procedures, the systematic study of glass formation and crystallization kinetics is limited by these experimental capabilities. By employing the thin-film architecture of the parallel nano-scanning calorimeter (PnSC), we perform calorimetric characterization of glass formation, crystallization, and melting with 102 – 104 K/s heating and cooling rates. These experiments are performed over an array of 22 compositions in the glass-forming system Au-Si-Cu. X-ray diffraction (XRD) experiments provide characterization of the crystalline and amorphous components of as a function of quench rate and composition. Combining these XRD results with PnSC enables to decode in an effective manner the complex crystallization of these alloys. More generally, the power of combining these experimental techniques will be discussed not only in the context of materials characterization, but also with regard to the high-throughput probing of glass physics.
Friday, October 14, 2011 “Novel” Materials
THE EFFECT OF TOPOGRAPHY FEATURES ON MODULUS MAPPING OF NANOSCALE INTERFACES IN A DEEP SEA SPONGE
Igor Zlotnikov, Department of Biomaterials, Max Planck Institute of Colloids and Interfaces Am Mühlenberg 1 OT Golm, Potsdam, N/A, 14424, Germany
T: +49-331-567 9453, F: +49-331-567 9402, [email protected] Haika Drezner, Doron Shilo, Faculty of Mechanical Engineering, Technion, Haifa, Israel
Yannicke Dauphin, Micropaléontologie, UFR TEB, Université P. & M. Curie, Paris, France Emil Zolotoyabko, Faculty of Materials Engineering, Technion, Haifa, Israel
Barbara Aichmayer, Peter Fratzl, Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany
NanoDMA-based (Dynamic Mechanical Analysis) modulus mapping technique has been shown to be efficient in quantitatively mapping the mechanical properties of submicron features in several different materials. Local properties, storage and loss moduli, are evaluated based on Hertzian contact mechanics of the sample-tip configuration. However, Hertzian approach requires a smooth surface, pure elastic contact and material homogeneity; hence, the topography and features size of a sample may have a pronounced effect on the obtained results. The most common origin of topography formation in composite structures is the sample preparation procedure, in particular surface polishing. Softer components are polished faster than harder ones which results in groove formation that eventually leads to deviations from pure Hertz contact and, hence, inaccurate analysis of mechanical characteristics. This effect is even stronger in case of inclusions, having the sizes on a hundred nanometer scale (i.e. close to the radius of the indenter tip). These considerations are illustrated through the study of the anchor spicule of the deep sea sponge, Monorhaphis chuni. Cross section of the spicule consists of relatively thick (2-10 µm) biosilica cylinders centered around organic filament and separated by thin (less than 100 nm) organic layers. The elastic modulus of the organic part is expected to be one order of magnitude lower than that of the biosilica. These properties make the spicule a good candidate for nanoDMA modulus mapping and for demonstration of the potential effect of topography and features size on deviation from Hertzian approach and on obtained results. Modulus mapping of cross-sections of M. chuni spicules was complemented by finite element analysis (FEA) of the mapping procedure. A model was constructed based on surface topography, as measured by tapping mode AFM, and on the thickness of the organic layers, as determined by back-scattered electrons (BSE) in a scanning electron microscope (SEM). The elastic modulus of the organic phase and the characteristics of the biosilica-organic interface were estimated by fitting FEA simulations to the experimental results.
Friday, October 14, 2011 “Novel” Materials
TEMPERATURE DEPENDENCE OF VISCO-ELASTIC PROPERTIES OF POLYMER THIN FILMS USING NANOINDENTATION
Diana Courty, ETH Zurich Wolfgang-Pauli-Strasse 10, Zurich, 8093, Switzerland
T: +41 44 633 6915, F: +41 44 632 1101, [email protected] Ralph Spolenak, ETH Zurich
Nanoindentation is a powerful tool to determine material properties, like hardness and Young's modulus. Using more elaborate testing techniques like Dynamic Mechanical Analysis (DMA) nanoindentaion also gives access to complex material properties like the glass transition temperature of a polymer thin film. The mechanical properties of spin-coated polymer thin films (thickness below 100 nm) like PMMA (Poly(methyl methacrylate) on silicon substrates with 50 nm SiO2 layer are analysed. DMA nanoindentation measurements from room temperature to 200°C are performed comparing the evolution of the visco-elastic properties, like the loss factor tan δ, which is the relation between viscous and elastic modulus. It is shown that DMA measurements can be used to determine the loss maximum for different film thicknesses, which can be usually related to the glass transition temperature. Higher transition temperature is found for thinner films, as has also been shown by Petitdidier et al.. Furthermore, a nanoindenter module applied to an AFM is used to resolve the exact relation between signal and response. Heating tests in the AFM are planned to be able to compare directly the phase lag between stored and lost energy tan δ for different temperatures. The comparison of both methods gives valuable insight on the reliability of data treatment in classical nanoindenters.
Friday, October 14, 2011 “Novel” Materials
MULTISCALE APPROACH TO PLASTIC DEFORMATION OF SILICATE GLASSES AT THE MICRON SCALE
Etienne Barthel, CNRS/Saint-Gobain 39 Quai Lucien Lefranc, Aubervilliers, 93330, France
Silicate glasses experience plastic deformation at the micron scale, a crucial issue for the practical strength of these ubiquitous materials. However the micromechanics tools for a better experimental characterization of plastic deformation at the micron scale have become available only recently. Simultaneously, understanding of the elementary plastic deformation mechanisms has been recently facilitated by the progress of Molecular Dynamics. In this respect, we note that in terms of mechanisms for plastic deformation, silicate glasses bear a lot of similarities to Bulk Metallic Glasses, but that they are singular in the substantial free volume they enjoy, which allows for permanent volumetric deformation (densification). Here we show how we combine continuum scale measurements [1] with molecular Dynamics (MD) simulations [2] for a better understanding of the plastic deformation of silicate glasses.
On the experimental side, the specific feature of silicate glasses is brittleness at large scales so that experiments probing the plastic response must be carried out at the 10 micrometer scale or below. To probe deformation at these lengthscales we use Raman or luminescence spectroscopy under various types of loadings. In situ Raman microspectroscopy experiments were performed under hydrostatic compression in a diamond anvil cell. Post indentation deformation maps were obtained on microindents. Recently, we have developed micro-pillar experiments to probe a reasonably well defined stress state with significant shear. Etching of the pillars was carried out by Reactive Ion Etching and the design was analyzed by Finite Element Modeling (FEM), taking into account contact conditions, misalignment and substrate compliance [3].
To model the plastic response at the continuum lengthscale, FEM analysis of the data has been carried out to infer a quantitative constitutive equation for silica, taking into account both densification and strain hardening. At the atomistic scale, Molecular Dynamics simulations were carried out, using a BKS (Wolf truncated) potential, which is thought to be a good approximant for silica. In these MD simulations, we have performed shear experiments at fixed hydrostatic pressure to identify the yield surface and hardening of the materials. We show that a very reasonable match with the continuum scale constitutive equation is obtained. At the same time, the MD results suggest possible improvements in the form of the constitutive relation used for FEM. We believe this direct dialog between MD and continuum scale approaches is successful because there is no intermediate lengthscale in these amorphous materials.
[1] G. Kermouche, E. Barthel, D. Vandembroucq and P. Dubujet, Acta Materialia 56 (2008) 3222-3228. [2] A. Tanguy, B. Mantis and M. Tsamados EPL 90 (2010) 16004. [3] V. Chomienne, G. Kermouche, J. Teisseire, S. Queste and E. Barthel, Scripta Mat., submitted.
Posters
Nanomechanical Testing in
Materials Research and Development
October 9-14, 2011
Lanzarote, Canary Islands, Spain
Poster Presentations
1. Synthesis and characterization of bundle-like CeO2 nanofibers
Ruixing Li, Beihang University, China
2. Determination of fracture properties of (Pt,Ni)Al bond coats by microbeam bend tests Jaya B Nagamani, Indian Institute of Science, India
3. Deformation mechanisms of nanocomposite metals composed of a Cu matrix reinforced by Nb nanowhiskers studies by in-situ deformation in the TEM and under synchrotron beam Ludovic Thilly, University of Poitiers, France
4. Mechanical properties of superelastic hard carbon materials produced by high-pressure high-temperature treatment of fullerenes Olga P. Chernogorova, Baikov Institute of Metallurgy and Materials Sciences RAS, Russia
5. Nanoindentation applied to ion-irradiated iron-chromium alloys Frank Bergner, Helmholtz-Zentrum Dresden-Rossendorf, Germany
6. Deformation behavior of miniaturized copper bicrystals and corresponding dislocation boundary interactions Peter J. Imrich, Austrian Academy of Sciences, Austria
7. Mechanical behavior of reaction wood: A multiscale approach Rejin Raghavan, EMPA Materials Science and Technology, Switzerland
8. Preparation and characterization of aluminum - fullerene composite Vladimir V. Milyavskiy, Joint Institute for High Temperatures of RAS, Russia
9. In situ evaluation of pile-ups height during scratch hardness test Alex Useinov, Technological Intitute for Superhard and Novel Carbon Materials, Russia
10. Mechanical properties, structure and shock behavior of yttria-doped tetragonal zirconia Vladimir V. Milyavskiy, Joint Institute for High Temperatures of RAS, Russia
11. Electromechanical test of single-wall carbon nanotube thin film Won Seok Chang, Korea Institute of Machinery and Materials, Korea
12. Investigation of the fracture of thin amorphous alumina films during spherical nanoindentation David Mercier, CEA-LETI Minatec, France
13. Fracture modes in micropillar compression Philip R. Howie, University of Cambridge, United Kingdom
14. Plasticity in brittle intermetallics William J. Clegg, University of Cambridge, United Kingdom
15. Interaction between the indentation size effect and the Hall-Petch effect in polycrystalline zirconia Andy Bushby, Queen Mary University of London, United Kingdom
16. Novel preparation methods for silver nanoparticles with precise control over size and shape Jignasa Solanki, S. V. National Institute of Technology, India
17. TEM investigations of the formation of martensite during nanoindentation of an austenitic NiTi shape memory alloy Janine Pfetzing-Micklich, Ruhr University Bochum, Germany
18. AFM-based indentation in KBr(100): Measurement of homogeneous dislocation nucleation
in three dimensions and Time dependent plasticity Robert Gralla, INM - Leibniz Institute for New Materials, Germany
19. Elastic nanoindentation experiments with mixed load and superposed mixed vibration for the determination of Young's modulus and Poisson's ratio Andre Clausner, Chemnitz University of Technology, Germany
20. Hardness and elastic modulus gradients in plasma nitrided 316l polycrystalline stainless steel investigated by nanoindentation tomography Christoph Tromas, Université de Poitiers, France
21. Synchrotron-based in situ mechanical testing of nanocrystalline metals and alloys Jochen Lohmiller, Karlsruhe Institute of Technology, Germany
22. Mechanical properties of self-assembled nanoparticle arrays Anna Campbellova, Czech Metrology Institute, Czech Republic
23. Natural bio-ceramic nano composites, Strombus gigas conch shell: The hierarchical microstructure and the mechanical properties Yoon Ah Shin, Pohang University of Science and Technology, Korea
24. Combined characterization of thin films using scanning probe microscopy and nanoindentation Oleg Lysenko, Institute for Superhard Materials, Ukraine
25. Natural bio-ceramic nano-composites: The hierarchical microstructure and the mechanical properties of nacre Subin Lee, Pohang University of Science and Technology, Korea
26. Dislocation plasticity of Au nanowires under strain gradient condition observed by in-situ TEM compression Jiseong Im, Pohang University of Science and Technology, Korea
27. Modulus mapping of implant microcomposites Erik F.-J. Rettler, Friedrich-Schiller-University Jena, Germany
28. Experimental determination of the effective indenter shape and epsilon factor for nanoindentation Benoit Merle, University Erlangen-Nürnberg, Germany
29. Fatigue testing of gold thin films with the bulge test Benoit Merle, University Erlangen-Nürnberg, Germany
31. Heat- and erosion-resistant nanostructured coatings for the compressor blades of gas turbine engines Aleksandrs Urbahs, Riga Technical University, Latvia
33. A method to estimate the cone indentation hardness of materials from their rheological schemes Gaylord Guillonneau, LTDS Ecole Centrale de Lyon, France
34. Local identification of the stress-strain curves of metal materials at a high strain rate using
repeated micro-impact testing Gaylord Guillonneau, LTDS Ecole Centrale de Lyon, France
35. Micro-tensile test of nano-thick thin film specimen fabricated by transferring process Bongkyun Jang, Korea Institute of Machinery & Materials, Korea
36. Strain rate sensitivity effects on the failure of metal films on compliant substrates Megan J. Cordill, Austrian Academy of Sciences, Austria
37. Adequateness of the effectively shaped indenter approach for the determination of yield strength Frank Richter, Chemnitz University of Technology, Germany
38. Preparation of novel polyimide nanofoams and investigation of their physical and mechanical properties Elham Aram, Iran Polymer and Petrochemical Institute, Iran
39. Direct measurement of contact area during spherical indentation of viscoelastic polymers Andy Bushby, Queen Mary University of London, United Kingdom
40. Determining real indenter geometry in spherical nanoindentation taking into account infinitesimal deformation of the indenter Young-Cheon Kim, Seoul National University, Korea
41. Nanoindentation testing of Ti6Al4V nanolayers modified by ion beam Methods Frantisek Cerny, CTU in Prague, Czech Republic
42. Influence of pre-existing dislocations on the pop-in phenomenon during nanoindentation in MgO Christoph Tromas, Université de Poitiers, France
43. Fracture testing – from the microscale to macroscale David E.J. Armstrong, University of Oxford, United Kingdom
44. Micro-cantilever tests of strengthening from α/α and α/β boundaries in titanium alloys Jicheng Gong, University of Oxford, United Kingdom
45. Nanoindentation study of homo-epitaxied 4H-SiC single crystals: the effect of doping Jacques Rabier, Université de Poitiers, France
46. Effect of in situ hydrogen charging on the pulsed plasma nitiding layer in stainless steels Afrooz Barnoush, Saarland University, Germany
47. Direct evaluation of dislocation networks and dislocation density tensors from atomistic data Christoph Begau, Ruhr-University Bochum, Germany
48. Onset of plasticity in silicon nanowires Ludovic Thilly, Université de Poitiers, Framce
49. Deformation analysis of vertically aligned carbon nanotube bundles under uniaxial compression Shelby B. Hutchens, California Institute of Technology, USA
50. Micromechanical testing of stress corrosion cracking behaviour at individual Grain boundaries in stainless steel Alisa Stratulat, University of Oxford, United Kingdom
51. Investigation of the size dependent mechanical behavior of α-FE and non-alloyed DC04
steel Simone Schendel, Karlsruhe Institute of Technology, Germany
52. Effect of specimen size on the tensile strength of WC-Co hard metal Thomas Klünsner, Materials Center Leoben Forschung GmbH, Austria
53. Observation of dislocation-movement in passivated Al film using in situ transmission electron microscopy nanoindentation Ludvig de Knoop, CEMES-CNRS, France
54. 3D-Experimental study of the formation of slip bands near boundaries in bicrystals with small dimension Afrooz Barnoush, Saarland University, Germany
Poster Number 1
SYNTHESIS AND CHARACTERIZATION OF BUNDLE-LIKE CEO2 NANOFIBERS
Ruixing Li, Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University
School of Materials Science and Engineering, Beihang University, 37 Xueyuan Road, Haidian District, Beijing, 100191, China
T: 86-10-8231-6500, F: 86-10-8231-6500, [email protected] Cong Fu, Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of
Materials Science and Engineering, Beihang University Xiaozhen Song, Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School
of Materials Science and Engineering, Beihang University Mingjie Gu, Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of
Materials Science and Engineering, Beihang University Zhihai Feng, Aerospace Research Institute of Materials & Processing Technology, No. 1 Nan Da Hong
Men Road, Fengtai District, Beijing 100076, China
The simultaneous control of size, morphology, and size distribution of particles is a challenging topic for nanoparticles synthesis, and one-dimensional (1-D) nanostructures have attracted increasing attention due to their specific properties. In the present study, 1-D CeO2 was synthesized synergistically by aging pretreatment and solvothermal methods using Ce(NO3)3 ·6H2O and CO(NH2)2 in ethanol without the use of any template or surfactant.
A SEM study revealed 1-D CeO2 fibers with perfect profile, well-dispersed state, and more uniform size distribution. The diameter of the fibers was about 50 nm and the length was 200 - 800 nm. An in-depth TEM observation revealed that a 1-D profile was formed by agglomeration of large numbers of nanoparticles during an early stage of the reaction. Then, the nanoparticles were gradually fused together to form a 1-D fiber with a smooth surface and a sub-microstructure, namely, the CeO2 fibers were assembled from many sub-nanofibers. Clearly, the CeO2 nanoparticles connected with each other via the oriented attachment mechanism and a reduction in surface free energy was achieved by the complete removal of pairs of surfaces. With an increase in reaction time, adjacent nanoparticles fused together to form strong links resulting in the evolution of bundle-like CeO2 nanofibers and the decrease of overall energy. Imperfect oriented attachment of nanocrystals can generate dislocations with edge, screw, and mixed character. Because initial nanocrystals were defect free, any defects observed by HRTEM can be attributed to the growth process.
Poster Number 2
DETERMINATION OF FRACTURE PROPERTIES OF (PT,NI)AL BOND COATS BY MICROBEAM BEND TESTS
Nagamani Jaya B, Indian Institute of Science IISc, Bangalore, Karnataka, 560012, India
T: 919241801604, F: 08022933243, [email protected] Vikram Jayaram, Indian Institute of Science
Pt modified NiAl bond coats are diffusion aluminides coated on superalloy based turbine blades in aero engines and gas turbines as oxidation resistant barriers. Being B2 intermetallics, they are known to be brittle which causes them to crack both on the surface during erosion and at the interface with the substrate due to thermal mismatch stresses. These act as starting points for the failure of the turbine blade itself. Hence determination of fracture properties at individual zones of the gradient coating becomes important. Characterisation studies on 5PtAl coatings reveal four distinct zones with heterogeneous microstructure. Microscale testing has been adopted in the present study due the small scale nature of the coating which does not allow for bulk tests. Extracting local properties requires machining of beams confined to particular isolated zones.
In order to study crack trajectories and determine variation in fracture strength and toughness across the thickness, we have devised microbeam bend tests based on doubly clamped and single cantilever geometries. 100*20*15 &mu m beams are milled using FIB at different zones. Lack of standards at such small length scales compels us to draw confidence from mechanical tests carried out by the MEMS community at large. Sharp notches are milled at low currents in FIB to act as starter cracks. Wedge loaded nanoindenter set up is used to load them to fracture under bending. Loads at pop-in are used to calculate fracture strength in unnotched beams and fracture toughness in notched ones. Crack trajectories are recorded from beams where crack arrests prevent catastrophic failure. Finite element analysis of these micron sized beams reveals the stress distribution across the beam which is then incorporated into formulations of KI for clamped beams. Results from both single edge notch bend and edge notched cantilevers show a rise in fracture toughness across the thickness of the bond coat from top to bottom. Since high temperature nanoindentaion tests upto 400oC show a drop in modulus and hardness we are looking towards extending these experiments to higher temperatures to observe associated changes in strength and fracture toughness.
Novelty of the experimental set up, problems encountered in loading at small scales and possible geometrical and microstructural reasons for the observed changes in crack paths along with quantitative values obtained for toughness will be discussed.
Poster Number 3
DEFORMATION MECHANISMS OF NANOCOMPOSITE METALS COMPOSED OF A CU MATRIX REINFORCED BY NB NANOWHISKERS STUDIES BY IN-SITU DEFORMATION IN THE TEM AND
UNDER SYNCHROTRON BEAM
Ludovic THILLY, University of Poitiers Institut Pprime, SP2MI, Bd Curie, Futuroscope Chasseneuil, 86962, France
T: 33 5 49 49 68 31, F: 33 5 49 49 66 92, [email protected] Steven VAN PETEGEM, Paul Scherrer Institute, Villigen, Switzerland
Florence LECOUTURIER, LNCMI, Toulouse, France Pierre-Olivier RENAULT, Pprime Institute, University of Poitiers, Futuroscope, France
Helena VAN SWYGENHOVEN, Paul Scherrer Institute, Villigen, Switzerland
High strength and high electrical conductivity nanocomposite wires composed of a Cu matrix reinforced by Nb nanowhiskers or Nb nanotubes are prepared by severe plastic deformation, applied with an Accumulative Drawing and Bundling process (ADB), for the windings of high pulsed magnets. The ADB process leads to a multi-scale Cu matrix containing up to N=854 (52.2 106) continuous parallel Nb filaments or tubes with diameter down to few tens nanometers. After heavy strain, the Nb nanowhiskers or nanotubes exhibit a dislocation free microstructure. The Cu matrix presents a multi-scale microstructure with multi-modal grain size distribution from the micrometer to the nanometer range. The use of complementary characterization techniques at the microscopic and macroscopic level (in-situ tensile tests in the TEM and in-situ tensile tests under high energy synchrotron beam) shed light on the role of the multi-scale nature of the microstructure in the recorded extreme mechanical properties, in particular with the presence of phase-specific elastic-plastic regimes in direct relation with size characteristics [Acta Materialia 57 (2009) 3157-3169].
Poster Number 4
MECHANICAL PROPERTIES OF SUPERELASTIC HARD CARBON MATERIALS PRODUCED BY HIGH-PRESSURE HIGH-TEMPERATURE TREATMENT OF FULLERENES
Chernogorova O.P., Baikov Institute of Metallurgy and Materials Sciences RAS Leninskii pr. 49, Moscow, 119911, Russia
Superelastic hard materials with a high hardness-to-elastic modulus ratio show promise for wear-resistant and low-friction components. The determination of hardness for such materials is a problem since generally no indent suitable for measurement is seen at their surface because of high elastic recovery. Bulk particles and samples of superelastic hard phase (SHP) were obtained from fullerenes at a pressure of 3 – 8 GPa at temperatures of 1100-1500 K. Their hardness was measured by the methods of macro-, micro-, and nanoindentation. According to the microindentation data obtained with a CETR universal tester recording the loading-unloading curves (treated by the Oliver-Pharr method), the SHP particles are characterized by high hardness (up to 35 GPa), high elastic recovery (85-94%), and relatively low elastic modulus (60-150 GPa). A universal microhardness of up to 28 GPa was measured with a PMT-3 tester by a specific method permitting the evaluation of total (elastic and plastic) deformation under load. An increase in load upon microindentation from 0.2 to 2 N decreases the hardness measured with the CETR and PMT-3 devices by a factor of 1.5 and 1.25, respectively. The cracking resistance of the SHP particles was estimated with a Vickers tester at a load of up to 200 N. After Vickers indentation, no radial cracks have been observed on the particle surface, and the residual deformation limited by the contact area between the particle surface and the diamond indenter was expressed by weak crossing grooves left by the edges of the diamond pyramid and small cracks parallel to the pyramid base in the areas corresponding to the pyramid faces. This shows the ability of the SHP particles to withstand heavy contact loads without any severe residual deformation and without any fracture propagation beyond the contact area.
Poster Number 5
NANOINDENTATION APPLIED TO ION-IRRADIATED IRON-CHROMIUM ALLOYS
Frank Bergner, Helmholtz-Zentrum Dresden-Rossendorf P.O.Box 510119, Dresden, 01314, Germany
Ferritic and ferritic/martensitic chromium steels are candidate structural materials for future nuclear applications such as fusion reactors, generation IV fission reactors and transmutation systems. Moreover, they constitute the matrix of oxide dispersion strengthened chromium steels under consideration. Qualification of these kinds of steels for future application requires improved physical understanding of the effect of chromium on the microstructure, properties and irradiation behaviour. More specifically, the evolution of irradiation-induced dislocation loops, the irradiation-enhanced formation of α’ phase particles, and the hardening caused by these features are among the issues of major interest.
To this end a set of commercial-purity iron-chromium alloys of chromium contents ranging from 2.5 to 12.5 at% was exposed to ion irradiations and characterized by means of nanoindentation. Self-ion irradiation is considered to be well suited for the simulation of neutron irradiation effects. The irradiation fluence and temperature were varied in the range from 1 to 50 displacements per atom and from room temperature to 500°C, respectively. Selected dual-beam irradiations using iron and helium ions are also included. Due to the limited penetration depth of ions of the order of 1 µm well-adopted characterization techniques such as nanoindentation have to be applied. Depth-resolved indentation testing using a Berkovich indenter was performed for a range of maximum loads from 1 to 500 mN. Details of the indentation process, the indentation size effect and the ratio of indentation depth and thickness of the irradiated layer were considered in order to extract the irradiation-induced hardening.
The results are discussed in terms of the effects of irradiation fluence, temperature and chromium level on radiation hardening. In order to identify the major hardening mechanisms, the results of microstructural investigations using transmission electron microscopy and small-angle neutron scattering were taken into account.
Poster Number 6
DEFORMATION BEHAVIOR OF MINIATURIZED COPPER BICRYSTALS AND CORRESPONDING DISLOCATION BOUNDARY INTERACTIONS
Peter J. Imrich, Erich Schmid Institute of Materials Science, Austrian Academy of Sciences Jahnstraße 12, Leoben, 8700, Austria
T: +433842804313, F: +433842804116, [email protected] Christoph Kirchlechner, Department Materials Physics, Montanuniversitaet Leoben
Xianghai An, Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences
Gerhard Dehm, Erich Schmid Institute of Materials Science, Austrian Academy of Sciences and Department Materials Physics, Montanuniversitaet Leoben
The interactions of dislocations with grain boundaries are relevant in numerous basic and advanced materials applications. For long time it has been known that decreasing the grain size of a metal leads to higher strength. This increase can be described by the Hall Petch equation and is due to the barrier effect that grain boundaries have on dislocations. While the continuum mechanical behavior can easily be described in macroscopic dimensions, the discrete interaction processes of dislocations with grain boundaries are complex and have not yet been totally understood.
Here we show the deformation behavior of miniaturized copper bicrystals. Compression tests on micrometer sized samples have been performed in situ in the scanning electron microscope (SEM) while recording force displacement data. The tested pillars were bicrystals with a sigma 3 boundary running along the compression direction and single crystals of the two individual grains. The single crystals deform as expected on discrete glide planes. The two grains of the bicrystals also deform on discrete, corresponding glide planes that coincide at the twin boundary. No offset between the associated glide planes can be seen at the boundary. Compared to the single crystalline compression samples the pillars show no increase in strength. To further understand the dislocations interactions transmission electron microscopy (TEM) measurements are carried out. In the talk the stress strain behavior will be discussed in respect to the corresponding microstructure.
Poster Number 7
MECHANICAL BEHAVIOR OF REACTION WOOD: A MULTISCALE APPROACH
Rejin Raghavan, Laboratory for Mechanics of Materials and Nanostructures,
EMPA Materials Science and Technology Feuerwerkerstrasse 39, Thun, 3602, Switzerland
T: 0041-332283703, F: 0041-332284490, [email protected] Silla Hansen,
Laboratory for Mechanics of Materials and Nanostructures, EMPA Materials Science and Technology
Tanja Zimmermann, Wood Laboratory,
EMPA Materials Science and Technology Johann Michler,
Laboratory for Mechanics of Materials and Nanostructures, EMPA Materials Science and Technology
Wood possesses a fascinatingly complex and hierarchical microstructure, which is not only appealing from a scientific perspective, but also provides insights for new man-made technological applications mimicking nature’s design. In response to mechanical stress developed due to environmental conditions, aggressive cell growth occurs in specific regions of the wood species in order to counteract the stress and provide stability, which is called reaction wood. While the structure of this part of the wood is understood to be different from the unstressed part, systematic investigations of the mechanical behavior of reaction wood are scarce.
In this study, the deformation of reaction wood, in compressive and tensile stress states, has been investigated at the nano- and microscale (cell wall) by nanoindentation and insitu SEM micropillar compression respectively, and macroscale by compression of mm-sized blocks. The cell-wall was interpreted as a fiber-reinforced composite, where lignin forms the matrix and cellulose microfibrils act as the reinforcement. Nanoindentation revealed that unlike hardness, the elastic modulus is sensitive to the microfibril angle (MFA). On the other hand, insitu SEM micropillar compression revealed that compression wood (CW) deforms via densification of the matrix, and the deformation of the tension wood (TW) occurs due to plastic buckling of the cellulose microfibrils. While the small scale testing provides insights into the structural (MFA) dependence of the mechanical response of individual cell walls, the macroscale testing elucidates the role of the cell wall interface during failure. Macroscale compression experiments show that CW fails in a brittle manner revealing almost intact cells on the fracture surface, while TW deforms by shearing and formation of a kink band. The deformation response of both CW and TW at macroscopic length scales was interpreted by using the Gibson and Ashby model of wood as a cellular solid.
Poster Number 8
PREPARATION AND CHARACTERIZATION OF ALUMINUM - FULLERENE COMPOSITE
V.V. Milyavskiy, Joint Institute for High Temperatures of RAS Izhorskaya 13 bldg 2, Moscow, 125412, Russia
T: +7(495)4832295, F: +7(495)4857990, [email protected] A.S. Soldatov, S. You, M. Mases, Department of Applied Physics and Mechanical Engineering, Lulea
University of Technology S.V. Dobatkin, O.P. Chernogorova, E.I. Drozdova, A.A.Baikov Institute of Metallurgy and Materials
Science T.I. Borodina, L.B. Borovkova, G.E. Valino, Joint Institute for High Temperatures of RAS
Aluminum – C60 fullerene composites were produced with the use of severe plastic deformation (SPD) through high-pressure torsion (HPT) at room temperature and pressure of 4 GPa. Aluminum ASD-6 and C60 powders were mechanically mixed and preliminary compacted using piston-cylinder pressure cell. The preliminary compacted specimens (compacts) had a diameter of 10 mm and a thickness of 1 mm. The compacts were placed between the anvils of HPT machine, subjected to high pressure, and then the upper anvil was rotated with respect to the stationary lover anvil at a rotation speed of 1 rpm. Rotation was terminated after 5 turns. Mass fraction of C60 fullerene in the composites was 10, 20 and 30 %. In addition, reference specimens were made only of pure Al ASD-6 and only of pure C60 powders. In the latter case, rotation was terminated after 3 turns because of extrusion of the material from the cavity. In order to study SPD-induced transformations in detail, two of specimens containing 20 % of C60 were produced with the use of reduced SPD procedure (two and three terns only).
Microstructure and mechanical properties of the specimens were characterized with the use of scanning probe microscope Solver P47 equipped with nanoindentation head, X-ray diffraction, scanning electron microscopy and Raman spectroscopy. Spatial-resolved maps of chemical composition of the specimens were studied, too.
Raman spectroscopy reveals that C60 molecules were not damaged by SPD. According to X-Ray data, an apparent grain size of aluminum crystals in the composite specimens decreases with the SPD intensity. Aluminum crystals on the surfaces of all specimens had preferable orientation. Microhardness of the specimens was up to 2.5 GPa and seems to be determined by the properties of the metal matrix.
The work was supported by the Swedish Institute (00906-2009).
Poster Number 9
IN SITU EVALUATION OF PILE-UPS HEIGHT DURING SCRATCH HARDNESS TEST
Alex Useinov, Technological Intitute for Superhard and Novel Carbon Materials 7a, Centralnaya str., Troitsk, Moscow region, 142190, Russia T: +74992722314, F: +74994006260, [email protected]
Hardness is one of the trickiest material properties. It depends on so many effects and conditions that proper hardness measurement is not a simple engineering or scientific task, but is almost an artistic act. To measure hardness Homo sapiens through all his history used either indentation or a scratch test. Most likely that the scratching appeared first, since scratch trace is better noticeable on the surface compared to indentation imprint with the same load. Friedrich Moohs used scratch to build his scale for hardness of minerals. But finally the age of scratching ended and age of instrumented indentation had begun. First years were wonderful and full of new exciting inventions. The “say no to imaging� principle had made this technique very popular at macroscopic and microscopic scales. However, when going to sub-micrometer length scale, the researchers faced some new effects that are not counted for in indentation. Pile-ups, sink-ins and cracks are among them. The essential solution to this problem is to see how the material behaves after the plastic deformation. This means – welcome to the imaging again, on the next circle of instruments evolution. In this situation the term “better noticeable� make the scratch test to compete with indentation like in good old times. Especially this situation takes place in applications to rough surfaces and low loads.
In the present work the scratch analysis was extended by combining the initial surface profile, the instrument compliance, thermal drift and indentor displacement during the test. As a result the indentor trajectory during the scratch test is reconstructed. Scratch trajectory was derived for several materials. It has been shown that after the initial penetration the indentor either stays on the same depth until the end of scratch or floats to some new level. This floating depends on the height of pile-up formed during the deformation. SPM imaging of the residual scratch traces confirmed this suggestion.
This analysis leads to the in situ estimation of pile-ups size and their influence on contact area and as a result on hardness evaluation.
Poster Number 10
MECHANICAL PROPERTIES, STRUCTURE AND SHOCK BEHAVIOR OF YTTRIA-DOPED TETRAGONAL ZIRCONIA
V.V. Milyavskiy, Joint Institute for High Temperatures of RAS Izhorskaya 13 bldg 2, Moscow, 125412, Russia
T: +7(495)4832295, F: +7(495)4857990, [email protected] A.S. Savinykh, Institute for Problems of Chemical Physics of RAS
E.S. Lukin, N.A. Popova, D. Mendeleyev University of Chemical Technology of Russia T.I. Borodina, F.A. Akopov, L.B. Borovkova, V.S. Ziborov, G.E. Valiano, Joint Institute for High
Temperatures of RAS
High-density, hard and durable, wear-resistant refractory materials based on partially stabilized zirconium dioxide (PSZD) are among the most perspective ceramics of new generation, having a complex of high performance behavior. High strength properties of PSZD ceramics are based on PSZD transformation reinforcement mechanism, which happens due to polymorphous transition of the tetragonal phase into the monoclinic phase, initiated in a stress field.
PSZD specimens were manufactured of fine-grained powders, obtained by a heterophased chemical deposition method. Microstructure and mechanical properties of the specimens were characterized with the use of scanning probe microscope Solver P47 equipped with the nanoindentation head, X-ray diffraction and scanning electron microscopy. The average size of sintered ceramics grains was 0.6 micron, the microhardness was 15 GPa. It was established that the ceramics consisted of 93 mass. % tetragonal and 7 mass. % monoclinic phase and had X-ray density of 6.18 g*cm-3.
Standard mechanical tests and ultrasonic measurements were performed, too. The manufactured ceramics had a density of 5.79 g*cm-3, a bending strength of 800 MPa, a crack resistance of 8 MPa*m0.5, a shearing modulus of 76 GPa, a compression bulk modulus of 162 GPa, Young's modulus of 198 GPa and Poisson's ratio of 0.3.
Properties of the PSZ ceramics at shock loading were tested with the use of explosive projectile systems and laser interferometer VISAR. The PSZD ceramics had shown high efficiency in Hugoniot elastic limit and spall strength.
Poster Number 11
ELECTROMECHANICAL TEST OF SINGLE-WALL CARBON NANOTUBE THIN FILM
Won Seok Chang, Korea Institute of Machinery and Materials 171 Jang-dong Yuseong-gu, Daejeon, Daejeon, 305-343, South Korea
T: +82-42-868-7134, F: +82-42-868-7884, [email protected] Chang Soo Han, Korea Institute of Machinery and Materials
Single-wall carbon nanotubes (SWCNTs) change their electronic properties when subjected to strain. In this study, the strain sensing characteristic of SWCNTs network is used to develop a transparent film sensor that can be used for strain sensing. Purified SWCNTs were grown by using the arc discharge technique. The SWCNTs samples were purified using standard processes, such as centrifugation, acid treatment, and membrane filtration. The SWCNTs were then dispersed in deionized water with a 1 wt % sodium dodecy sulfate (SDS) solution and sonicated for several hours. The SWCNTs network are formed on various plastic substrates such as poly(ethylene terephthalate) (PET), polyimide (PI) and polydimethylsiloxane (PDMS) using ink-jet and spray process. In this manner we could control the transparency and obtain excellent uniformity of the networked SWCNT film. The carbon nanotube film is isotropic due to randomly oriented bundles of SWCNTs. Using experimental results it is shown that there is a nearly linear change in resistance across the film when it is subjected to tensile stress. The results presented in this study indicate the potential of such films for multidirectional and multiple location strain sensors on macro scale.
Poster Number 12
INVESTIGATION OF THE FRACTURE OF THIN AMORPHOUS ALUMINA FILMS DURING SPHERICAL NANOINDENTATION
MERCIER David, CEA-LETI Minatec, Microsystems Characterization and Reliability Laboratory 17 Rue des Martyrs Cedex 9, Grenoble, Isère, 38054, FRANCE T: 0033438782340, F: 0033438785140, [email protected]
MANDRILLON Vincent, CEA-LETI Minatec, Microsystems Characterization and Reliability Laboratory VERDIER Marc, BRECHET Yves, VOLPI Fabien, Université de Grenoble, Lab. SIMaP-CNRS, BP 75, St
Martin d’Hères, F38402 Cedex, France PARRY Guillaume, ESTEVEZ Rafael, Université de Grenoble, Lab. SIMaP-CNRS, BP 75, St Martin
d’Hères, F38402 Cedex, France MAINDRON Tony, CEA-LETI Minatec, Microsystems Characterization and Reliability Laboratory
Thin amorphous alumina layers (10, 20, 30 & 40nm thick) are processed on sputtered aluminium thin films (500nm) by atomic layer deposition (ALD) at low temperature. Mechanical properties of the system are characterized by spherical nanoindentation with tip radius ranging from 0.5 µm up to 50 µm.
Indentation load driven-displacement curves display a plateau (“pop-in”) at a critical load and critical indentation depth. A statistical approach is used to determine these parameters. Careful SEM and AFM observations of indentation imprint show circumferential cracking in agreement with the assumption that the pop-in event is predominantly controlled by the fracture of the oxide film.
A model is developed to predict both the mechanical response prior to the oxide fracture and the corresponding pop-in event. The model is based on the assumption that during contact loading, the hard coating undergoes elastic deflection which includes both bending and membrane stretching effects, while the substrate undergoes elasto-plastic behaviour. Comparison with experiments allows the determination of oxide toughness.
Poster Number 13
FRACTURE MODES IN MICROPILLAR COMPRESSION
P.R. Howie, University of Cambridge Pembroke St, Cambridge, CB2 3QZ, UK
T: +44 1223 334339, F: +44 1223 334567, [email protected] S. Korte, University of Cambridge
W.J. Clegg, University of Cambridge
Whenever a sample is deformed beyond its elastic limit, plastic flow and brittle fracture act in competition. If micropillar compression is to be used as a technique for studying plastic behaviour in brittle materials, it is therefore important that the conditions under which fracture occurs are understood. Through-thickness axial splitting has been the most widely observed in previous work, however a number of other fracture modes are also seen. These are described and their underlying mechanisms discussed using conventional fracture mechanics. The dependence of each mode on material properties, test geometry and sample size is discussed in an attempt to define the regimes within which each mechanism can dominate.
Poster Number 14
PLASTICITY IN BRITTLE INTERMETALLICS
W.J. Clegg, University of Cambridge Pembroke St, Cambridge, CB2 3QZ, UK
T: +44 1223 334470, F: +44 1223 334567, [email protected] S. Korte, University of Cambridge
The study of plasticity in most high temperature intermetallics is impeded by their brittleness necessitating the suppression of cracking during testing. This is usually done by application of a confining pressure, for example using liquid or solid pressure media in uniaxial compression or the surrounding material in indentation. However, the first is time-intensive and difficult, while the latter does not allow a detailed study of plasticity in specific crystal directions, essential in complex and anisotropic crystals.
An alternative to the application of a confining pressure is the reduction of sample size to reduce the energy available in the specimen body to drive cracking. It has been shown that, by compression of micron-sized specimens, brittle materials can be deformed plastically even at room temperature to yield information on how plasticity is accommodated in the crystal and the critical resolved shear stresses on individual slip systems.
Here, the alloys of the Nb-Co system, from the plastic Nb2Co7 phase over the Laves phases to μ-Nb6Co7, are studied by microcompression and electron microscopy, giving quantitative yield stress measurements and a detailed study of how slip takes place, both in the very brittle Laves phases and the less well studied Nb2Co7 phase.
Poster Number 15
INTERACTION BETWEEN THE INDENTATION SIZE EFFECT AND THE HALL-PETCH EFFECT IN POLYCRYSTALLINE ZIRCONIA
Andy Bushby, Queen Mary University of London Mile End Road, London, E1 4NS, UK
T: +44 20 7882 5276, F: +44 20 7882 3390, [email protected] Temur Ahmad, Queen Mary University of London Ben Milsom, Queen Mary University of London Mile Reece, Queen Mary University of London
The indentation size effect, in which materials appear harder for smaller contact size, is now well established. Similarly, the Hall-Petch effect, where smaller grain size leads to higher yield strength, has been recognised since the 1950’s. Hou et al. (J. Phys D, 2008) showed that when the grain size of copper samples was similar in dimensions to the contact size, these two apparently separate size effects combine. They defined a new combine length scale that parameterised the flow stress for any combination of grain size and contact size. Dunstan et al. (Phys Rev Lett. 2009) showed a similar coupling of length scales in the torsion of thin wires. Here we show the same interaction between the indentation size effect, governed by the radius of the projected contact area, a, and the grain size, d, in polycrystalline zirconia. Zirconia powder containing 5.2wt% Yttria (TOSOH Japan) with a powder particle size of 30nm was rapidly consolidated by spark plasma sintering at temperatures of 1400 – 1800 degrees C to give grain sizes in the fully dense ceramic from 0.25 microns to 2.5 microns. These materials were indented with a series of spherical indenters ranging from 0.5 microns to 20 microns in radius. The partial unloading method was used to generate indentation stress-strain curves. The transition from elastic to plastic behaviour was unambiguous in this ductile ceramic. Yield pressures were determined using the method of Zhu et al. (J. Mech. Phys. Solid. 2008). The yield pressure was found to scale with the square root of (1/a + 1/d), as was found for copper. Furthermore the magnitude of the size effect was similar to that of copper. The symmetry in the coupling between the two length scales suggests a common origin of the size effects based on the mean free path of dislocations.
Poster Number 16
NOVEL PREPARATION METHODS FOR SILVER NANOPARTICLES WITH PRECISE CONTROL OVER SIZE AND SHAPE
Jignasa Solanki, S. V. National Institute of Technology, India S. V. National Institute of Technology, Ichhanath, Surat, Gujarat, 395 007, India
T: 0091 0261 2201642, F: 0091 261 2227334, [email protected] Z. V. P. Murthy, S. V. National Institute of Technology, India
Silver nanoparticles (SNPs) are very useful in many applications of industrial importance like catalytic, antimicrobial and heat transfer applications; however precise size and shape are necessary for successful applications. Accordingly, synthesis method offering precise control over size and shape is of major significance. The present study is focused on critically accessing recently used chemical/wet synthesis methods and their advantages and limitations. A novel method of synthesis, microemulsion method is then discussed in detail with synthesis parameters optimization for obtaining precise size, size distribution, and shape. The experimental work is carried out to synthesize SNPs inside nano-size water pools of w-o microemulsion, acting as special nano-reactor. Microemulsion is prepared with surfactant, di-octyl sodium sulphosuccinate (AOT). Synthesis of SNPs is then carried out by chemical reduction of silver nitrate and reducing agents, NaBH4 and N2H4, inside above mentioned special nano-reactors of microemulsion. The effect of most crucial operating parameter, water-to-surfactant molar ratio of microemulsion, on the product specification was investigated. The optimum water to surfactant molar ratio is suggested to obtain a desirable product specification. The particle size, shape and structures are analyzed by dynamic light scattering, transmission electron microscopy and UV-Visible spectroscopy. The effect of type of reducing agent on the size and size distribution of SNPs is also studied. Keywords: silver; nanoparticles; AOT; microemulsion technique.
Poster Number 17
TEM INVESTIGATIONS OF THE FORMATION OF MARTENSITE DURING NANOINDENTATION OF AN AUSTENITIC NITI SHAPE MEMORY ALLOY
J. Pfetzing-Micklich, Ruhr University Bochum, Institute for Materials Universitätsstr. 150, Bochum, 44780, Germany
T: +49 (0) 234 32 25934, F: +49 (0) 234 32 14235, [email protected] N. Wieczorek, Ruhr University Bochum, Institute for Materials
J. Frenzel, Ruhr University Bochum, Institute for Materials Ch. Somsen, Ruhr University Bochum, Institute for Materials G. Eggeler, Ruhr University Bochum, Institute for Materials
NiTi shape memory alloys (SMA) exhibit remarkable functional properties which are due to a reversible martensitic phase transformation that is associated with recoverable strains of about 6-8 %. Due to its superior mechanical properties NiTi alloys are used for components in advanced micromechanical systems like stents and micro-actuators. These applications require a detailed characterization of microscale properties like mechanical, and especially phase transformation behavior In previous studies, nanoindentation was performed to investigate local mechanical properties of NiTi SMA. Generally, the resulting data sets are not easy to analyze as they contain information on both elasto-plastic deformation and transformation induced deformation. The complex stress state with its high gradients seems to promote dislocation plasticity and impede the stress-induced transformation. In the present study we perform nanoindentation experiments on a specific NiTi alloy exhibiting the stress-induced phase transformation during loading, but only transforming back into austenite during unloading when an additional thermal activation proceeds. Post-mortem transmission electron microscopy (TEM) from the cross-section of the remnant indents allows for the first time the qualitative and quantitative analysis of the deformed volumes considering stress-induced martensite and dislocation plasticity. Subsequent in-situ heating in TEM (for the activation of the reverse transformation) gives rise of the reverse transformation into austenite and volumes containing residual martensite stabilized by a high dislocation density. These investigations provide new information about the required testing conditions for the local characterization of stress-induced phase transformations in SMA using nanoindentation.
Poster Number 18
AFM-BASED INDENTATION IN KBR(100): MEASUREMENT OF HOMOGENEOUS DISLOCATION NUCLEATION IN THREE DIMENSIONS AND TIME DEPENDENT PLASTICITY
Robert Gralla, INM - Leibniz Institute for New Materials Campus D2 2, Saarbrücken, Saarland, 66123, Germany
T: +49-681-9300-372, F: N/A, [email protected] Philip Egberts, INM - Leibniz Institute for New Materials, Department of Physics McGill University
Roland Bennewitz, INM - Leibniz Institute for New Materials
Direct comparison of experimental plasticity data and atomistic computer simulation is one factor pushing forward basic research in nanomechanics. Atomic force microscopy (AFM)-based indentation on single crystals is an ideal method by which plasticity experiments can be designed to match the constraints of atomistic simulation. The small tip radius typical of AFM probes allows for the mechanical testing on a nanometre-scale volume of material and the application of gigapascals of pressure. This construction also approaches a continuum mechanical point-like model. Furthermore, the high force resolution of AFM in both normal and lateral directions opens the opportunity to measure the displacement of the tip in three dimensions while performing a plasticity measurement.
Discontinuous displacements of the tip during indentation measurements, often referred to as pop-ins, are a result of the nucleation of dislocations in defect free, crystalline materials. In almost all materials glide of dislocations is not limited to one dimension. Rather, dislocation glide can occur in several crystallographic directions within the crystal. Using AFM-based indentation experiments with single dislocation resolution, the measurement of dislocation glide in KBr(001) crystals in three-dimensions has been achieved. Displacements of the tip normal to the surface and within the plane of the surface can be correlated with the preferred dislocation slip systems of the crystal.
In time-dependent experiments pop-ins were observed throughout indentation, up to 4 minutes after reaching the maximum load and holding it. Sharp silicon tips localized the stress at the surface, thereby increasing the measured pop-in displacement compared to blunt diamond-coated tips. In both cases, pop-in displacements were on the order of one Ångström or less. The observation of pop-ins throughout creep measurements indicates that creep in perfectly crystalline, nanoscale volumes can only be accommodated through dislocation nucleation and glide.
Poster Number 19
ELASTIC NANOINDENTATION EXPERIMENTS WITH MIXED LOAD AND SUPERPOSED MIXED VIBRATION FOR THE DETERMINATION OF YOUNG'S MODULUS AND POISSON'S RATIO.
André Clausner, Chemnitz University of Technology Reichenhainerstr. 70, Chemnitz, Saxony, 09126, Germany
T: 004937153136987, F: 004937153121719, [email protected] Frank Richter, Chemnitz University of Technology
In a wide range of applications materials can be considered either as a half space with isotropic properties or a stack of films with isotropic behaviour in each layer. Besides the Young's modulus the second elastic constant of such isotropic materials, for example the Poisson's ratio, is of interest to describe the complete elastic behaviour of a sample.
There are well known procedures to determine the Young's modulus from normal nanoindentation experiments, like the Oliver and Pharr Method for elastic-plastic curves or the Hertzian Fit for elastic curves. To determine a second elastic constant in thin films or bulk material a second independent experiment is needed.
The aim of this work is to investigate the capabilities of using a complete elastic nanoindentation experiment with mixed load (normal and lateral) and superposed mixed vibration additional to the experiment with normal load for this purpose.
Indentation experiments with mixed load have been performed using different spherical indenter tips. The results are shown for a range of materials including hard steel, ceramics and glasses.
The normal and the shear-stress distributions underneath the indenter as well as the stress fields in the specimen were calculated via FE simulations. As a result we saw here strongly asymmetric stress distributions, both, for the normal- and the shear-stresses at higher loads.
For a determination of the Poisson's ratio from the received mixed data, a fit of the ratio of normal to lateral stiffness using an analytical or numerical model of this special experiment has to be done. For this purpose, analytical solutions with varying boundary conditions from the literature were compared to the measurements to check their applicability.
Problems and restrictions due to the simplification and the limited sensitivity of these models are shown. With this information the possibilities and restrictions of a utilization of mixed nanoindentation experiments in order to determine the Poisson's ration are given.
Poster Number 20
HARDNESS AND ELASTIC MODULUS GRADIENTS IN PLASMA NITRIDED 316L POLYCRYSTALLINE STAINLESS STEEL INVESTIGATED BY NANOINDENTATION TOMOGRAPHY
C. Tromas, Institut P’, UPR 3346 CNRS – Université de Poitiers – ENSMA Département de Physique et Mécanique des Matériaux
Bât. SP2MI, Bd. Pierre et Marie Curie, BP 30179, Futuroscope Chasseneuil Cedex, 86962, France T: 0033549496724, F: 0033549496692, [email protected]
J.C. Stinville, C. Templier, P. Villechaise, Institut P’, UPR 3346 CNRS – Université de Poitiers – ENSMA Département de Physique et Mécanique des Matériaux
Austenitic stainless steel (ASS) suffers low hardness which can be enhanced by plasma nitriding. This treatment is performed at moderate temperature; typically around 400°C, to maintain the corrosion resistance of the ASS. The insertion of nitrogen leads to the formation of the metastable γN phase (or “expanded” austenite) within a layer several micrometers thick after a few hours of treatment.
In this study, the correlation between the grain orientation and the elastic properties of plasma nitrided polycrystalline ASS is investigated. Polycrystalline 316L ASS was plasma nitrided at 400°C for 8 h under a pressure of 7.5 Pa using a 60 sccm N2 and 40 sccm H2 mixture. The grain orientations (hkl) in a delimited area were obtained from electron backscatter diffraction (EBSD). Elastic modulus Ehkl and hardness Hhkl were obtained using nanoindentation tomography. The method consists in performing large regular indentation arrays (more than 1000 indents) in order to obtain hardness and elastic modulus mapping. By repeating this method in a same area after successive partial removals of the nitrided layer, the elastic modulus and hardness cartographies can be reconstructed in 3D, and compared to the nitrogen concentration, which depends on the crystallographic orientations of the investigated grains. The results show that plasma nitriding leads to a complete reversal of the elastic behavior anisotropy: while the non-nitrided 316L ASS shows the typical elastic anisotropy of fcc-type metals with a maximum of Ehkl for the <111> oriented grains, the maximum of Ehkl is observed for the <001> oriented grains in the nitrided layer. A similar anisotropy reversal is observed for the hardness. These observations are discussed on the basis of the microstructural changes induced by the nitrogen incorporation as well as the residual stress effects.
Poster Number 21
SYNCHROTRON-BASED IN SITU MECHANICAL TESTING OF NANOCRYSTALLINE METALS AND ALLOYS
Jochen Lohmiller, Karlsruhe Institute of Technology, Institute for Applied Materials Postbox 3640, Karlsruhe, BW, 76021, Germany
T: +49 721 608 2 5855, F: +49 721 608 2 2347, [email protected] Christian Braun, Manuel Grewer, Universität des Saarlandes, Lehrstuhl für Experimentalphysik
Veijo Honkimäki, European Synchrotron Radiation Facility, Materials Science Group Rainer Birringer, Universität des Saarlandes, Lehrstuhl für Experimentalphysik
Oliver Kraft, Patric A. Gruber, Karlsruhe Institute of Technology, Institute for Applied Materials
A prerequisite to exploit the unique mechanical properties of nanocrystalline (nc) materials is a thorough understanding of the underlying deformation mechanisms. In situ characterization is necessary in order to (i) detect reversible mechanisms and (ii) separate and ascribe the active mechanism to the respective strain regime. Therefore, special in situ shear compression tests are conducted on nc Ni, prepared by electrodeposition, and nc Pd alloys fabricated by inert-gas condensation. Applying load to shear compression specimens induces large homogeneous shear deformation (strain >20%) localized across a micromachined gauge section. In situ high energy synchrotron X-ray diffraction (XRD) enables observation of deformation modes in bulk samples during loading. A fast area detector allows for continuous recording of complete Debye rings, whereas total strain is determined by digital image correlation. X-ray line-profile analysis reveals two different stages of deformation: (i) elastic-microplastic behavior and (ii) macroplastic behavior. Different mechanisms, e.g. elastic grain interaction, grain rotation, grain boundary sliding or dislocation activity can be ascribed to the regimes, due to different evolution of peak shape parameters (special attention is paid to peak broadening, intensity and asymmetry parameters). Furthermore, peak broadening analysis allows determination of the coherent scattering volume (grain size) and microstrain. By varying the alloy composition of the continuous miscible Pd-Au system, the stacking fault energy, which is expected to influence the deformation behavior can be modified over a broad range. For Pd-70at%Au samples, in the first, so-called microplastic regime no texture evolves and the peak broadening is caused by an increase in microstrain. The second regime is characterized by an elastic strain plateau indicating macroplastic deformation. During macroplastic deformation an in-plane texture with 6-fold symmetry evolves and the grain size increases slightly with remaining equiaxed shape, while microstrain remains constant at its maximum value. The preservation of equiaxed grain shape and formation of texture suggest grain boundary mediated mechanisms as prevailing macroplastic deformation mechanism. This is supported by the fact that the grain interior (microstrain, constant elastic strain) is not affected during macroplastic deformation. In contrast, experiments on Pd-Au alloys with lower Au content show that the deformation mechanisms strongly depend on alloy composition, as e.g. Pd-10at%Au samples show negligible texture formation.
Poster Number 22
MECHANICAL PROPERTIES OF SELF-ASSEMBLED NANOPARTICLE ARRAYS
Anna Campbellova, Czech Metrology Institute Okruzni 31, Brno, 638 00, Czech Republic
T: 00420 545 555 337, F: 00420 545 555 183, [email protected] Petr Klapetek, Czech Metrology Institute
Nanoparticles are often encountered in many fields of research and technology, including materials research, medicine, biotechnology or enviromental sciences. If deposited on a flat substrate, monodispersed nanoparticles can form a closely packed self-assembled layer. This effect can be used not only for precise measurements of nanoparticle radii, but also for the development of many novel materials in the field of nanotechnology, biology or near-field optics. The study of mechanical properties of nanoparticle arrays can help understanding the basic phenomena of particle aggregation and self-assembled arrays formation. As the forces between the individual nanoparticles and between the nanoparticles and the substrate are very small, the mechanical properties of the whole assembly can be measured only using nanoscale force generation and sensing instruments. In this contribution we study mechanical properties of nanoparticle arrays deposited on flat silicon surfaces and formed by nanoparticles of different compositions (polymer, metallic) using an instrumented indention with a nanoindentor (UNHT, CSM Instruments). Results of experimental measurements are compared to modeling, performed using a simple dynamical model for particle motion based on Newton equations integration with appropriate potentials.
Poster Number 23
NATURAL BIO-CERAMIC NANO COMPOSITES, STROMBUS GIGAS CONCH SHELL : THE HIERARCHICAL MICROSTRUCTURE AND THE MECHANICAL PROPERTIES
Yoon Ah Shin, Pohang University of Science and Technology (POSTECH) SAN 31.HYOJA-DONG.NAM-GU, POHANG, GYUNGBUK, 790-784, South Korea
T: ++82 (0)10 4856 6024, F: ++82 (0)54 279 5155, [email protected] Subin Lee, Ga-Young Shin, Kung Song, Jiseong Im, Sang Ho Oh*, POSTECH
Strombus gigas conch which is native to the Carribean in Florida is one of natural ceramic-bio nanocomposites. It is known that Strombus gigas conch shell has remarkably high fracture toughness balanced by a modest level of strength although it is composed mostly of very brittle mineral (~99.9wt% CaCO3) and just a few organic component (~0.1wt%). The mineral component consists of single crystal grains of aragonite, the meta-stable orthorhombic polymorph of CaCO3.
In previous studies, it has shown that the toughness of conch shell is three orders of magnitude higher and the hardness is twice that of non-biogenic CaCO3. Its superior mechanical properties arise from its unique ¡°crossed-lamellar micro-architecture¡±, which involves the crystallites of aragonite sheathed in protein and bundled into criss-crossing beams. The present status of understanding of the microstructure has reached to a state to identifying the twinned building blocks of the shell, which was coined as ¡°third-order lamella¡± in literature, and suggesting several toughening mechanisms at macro- and meso-scales. However, due to the complicate hierarchical structures across several length scales, the toughening mechanisms are not understood thoroughly. Although it has been shown that there exist 10-20 nm-sized twins on the end-faces of third-order lamella, the role of twins in resisting crack propagation has not been studied previously.
In the present study optical microscopy (OM) and scanning electron microscopy (SEM) imaging has been used to examine the hierarchical nature of the microstructure of Strombus gigas conch shell. Our study aims to investigate how the twins influence the propagation of crack by performing in-situ transmission electron microscopy (TEM) nano-indentation test. Preparation of a suitable TEM specimen for mechanical testing, which also reveals all the microstructural details down to the third order lamella, is rather challenging because of the small size of the third-order lamellae embedded within the complicate micro-architecture. Successful implementation of in situ TEM experiments will elucidate the toughening mechanism at nanometer-scale, and show the real-time observation of the crack propagation process for the first time.
Poster Number 24
COMBINED CHARACTERIZATION OF THIN FILMS USING SCANNING PROBE MICROSCOPY AND NANOINDENTATION
O. Lysenko, Institute for Superhard Materials 2, Avtozavodskaya, Kiev, 04074, Ukraine
T: +380444676615, F: +380444688632, [email protected] S. Dub, A. Shcherbakov, Institute for Superhard Materials, Ukraine
G. Tolmachova, Kharkov Institute of Physics and Technology, Ukraine G. Abadias, Université de Poitiers, France
G. Mamalis, Project Centre NRC Demokritos, Greece
Recent development in Scanning Probe Microscopy (SPM) with diamond tip allows performing surface nanomechanical characterization. Surface hardness can be determined by measuring the topography of an indent, namely projected contact area, using SPM. More traditionally, nanoscale hardness is determined from the analyses of unloading curve without measuring of projected contact area directly. This method, however, does not take into account certain on-surface effects (pile-up, pop-in etc.) that take place while loading. Proposed method employing combined SPM indentation/scanning technique is expected to produce more adequate results on non-perfect and non-homogeneous surfaces but it has to be proven by comparative analysis of the hardness of the same surface obtained with both techniques. Our work presents the results of studies of TiTaN thin films on silicon substrate with scanning probe microscopy and nanoindentation method. Nano Indenter G200 and SPM with Berkovich diamond tip were used. Scanning has been performed in tunneling current mode. This approach, unlike the atomic-force microscopy method, avoids the dependence of resolution on the tip’s radius. In our experiments the surface topography studied with the resolution better than 1 nm. The results of the hardness studies by using both indent projection and the Oliver and Pharr methods with the indent’s depth ranging from 40 nm to 400 nm are shown and the influence of the scaling factor and the shape of indent are discussed. Additional features of combined studies to determine the adhesion and yield strength of thin films are shown.
Poster Number 25
NATURAL BIO-CERAMIC NANO-COMPOSITES: THE HIERARCHICAL MICROSTRUCTURE AND THE MECHANICAL PROPERTIES OF NACRE
Subin Lee, POSTECH San 31, Hyoja-dong, Nam-gu, Pohang, 790-784, Korea
T: 82-(0)10-4876-9208, F: 82-(0)54-279-5155, [email protected] Yoon Ah Shin, Kyung Song, Jiseong Im, Ga-Young Shin, Sang Ho Oh*, POSTECH
Nacre (mother-of-pearl) from mollusk shell has attracted considerable research interests of biomimetics community due to its well balanced combination of high strength, low weight, and fracture toughness which are generally incompatible in manmade materials. Nacre is well known as ¡®brick-and-mortar¡¯ structure which composed of aragonite (CaCO3) plate and thin layer of organic material. Most of research efforts have been directed to reveal the hierarchical structure of nacre across the multi-length scale and the underlying mechanisms of toughening. Since the modeling based simulation as well as the artificially synthesized nacreous materials are all failed to reproduce the genuine property of nacre, it is speculated that there must be unknown factors hidden in nanometer-scale which play a key role in improvement of fracture toughness. A promising way to get insight into the multi-length scale microstructure and the deformation behaviors of nacre can be provided by in situ deformation in transmission electron microscope (TEM), which enables direct observation of crack propagation and the response of aragonite plates and organic layers under the applied stress.
In this presentation, we report preliminary results from our on-going research program on the atomic-scale structure analysis and in situ TEM deformation of nacre. We investigated the microstructure and defects present in aragonite plates by conventional TEM, the inter-plate misorientation between neighboring aragonite plates by electron backscattered diffraction (EBSD). The single aragonite plate which has been regarded as a homogeneous defect-free CaCO3 was revealed to contain structural defects such as twins and some organic material embedded with the CaCO3 matrix. It appears that these structural features play a significant role in determining the mechanical properties of nacre. We will present the real-time TEM observations of the deformation behavior and the propagation of crack tip and address the origin of high fracture toughness of nacre.
Poster Number 26
DISLOCATION PLASTICITY OF AU NANOWIRES UNDER STRAIN GRADIENT CONDITION OBSERVED BY IN-SITU TEM COMPRESSION
Jiseong Im, POSTECH San31 Hyoja-Dong Nam-gu, Pohang, Kyungbuk, 790-784, South Korea
Recently, an unexpected size effect was discovered in single crystal deformation; the strength increases as the crystal size decreases below a micrometer. For single crystalline metals with the size of nanometer range, the mechanical properties(e.g. Young¡¯s modulus, yield strength, plastic flow) become complex functions of size, shape, defects and crystallographic orientation of the crystal. Fundamental understanding of such size effects calls for the direct observation of dislocation activities during the deformation of nanometer-sized crystals.
In this study, we aimed to elucidate the size effect of single-crystalline metals through in-situ TEM deformation test of Au nanowires. The Au nanowires were grown epitaxially on a SrTiO3 (110) substrate by vapor transport method. By using a nanoindentation TEM holder, the force-displacement curves were obtained while observing the generation and movement of dislocations during compression. Preliminary tests showed that the yield strength of an Au nanowire with the diameter of ~150 nm amounts to ~1 GPa. After yielding, the plastic flow of the nanowire comes into discrete slip bursts with surface steps formation.
The Au nanowires were grown along the [110] direction. The sidewalls of the nanowire are bounded mainly by four parallel {111} facets, resulting in a rhombic cross-sectional shape. The top end of Au nanowire is not flat but faceted by inclined {111} facets. When the flat punch is brought into contact with the top end of nanowire, the contact area starting from a line increases gradually with deformation. At this condition, the strain gradient sets up along the radial as well axial directions of nanowire. Dislocations were emitted preferentially at the punch/nanowire contact region into half-loop forms. In the beginning the dislocations glide and escape the crystal on the inclined {111} slip planes with creating slip steps. This behavior agrees well with the predictions by dislocation starvation or dislocation exhaustion theories. Unexpectedly, some of the emitted dislocations, taking spiral or dipole-like line shapes, glide down on the parallel {111} planes extending along the nanowire axis at a regular interval. It seems that these dislocations originate to compensate the strain gradient, which are similar to so-called the geometrical necessary dislocations observed during nanoindentation. Further details on the dislocation activities will be discussed in the conference.
Poster Number 27
MODULUS MAPPING OF IMPLANT MICROCOMPOSITES
Erik F.-J. Rettler, Laboratory of Organic and Macromolecular Chemistry (IOMC), Jena Center for Soft Matter (JCSM), Friedrich-Schiller-University Jena Humboldtstr. 10, Jena, N/A, D-07742, Germany
T: +49(0)3641948216, F: N/A, [email protected] Dirk Linde, Gerlind Schneider, HNO im Klinikum der FSU Jena, Biomaterials Laboratory
Ulrich S. Schubert, Laboratory of Organic and Macromolecular Chemistry (IOMC), Jena Center for Soft Matter (JCSM), Friedrich-Schiller-University Jena
New methacrylate-based microcomposites for bone-implants are under investigation by depth-sensing indentation. These materials are intended to replace defective bone tissue after surgery and bear the forces the defective bone is exposed to until natural healing has occurred and the implant can be removed. Thus, the materials should be bio-compatible and their mechanical properties should resemble natural bone tissue.
The composites investigated in this approach consist of a hard calciumphosphate phase embedded in a soft methacrylate polymer matrix. They are well-tolerated by the body, without being degraded or integrated into healthy tissue. Pure calciumphosphate implants have the advantage of being integrated into the bone but their use is limited due to the low mechanical strength. The investigated microcomposites combine the bio-compatibility of the phosphate component with the mechanical flexibility of the polymer.
In this approach, the mechanical properties are mapped by applying a large grid of measurement points. In choosing the appropriate grid spacing, overlapping of two deformation circles has to be avoided. Nearest-neighbor interpolation has been used to calculate the values between the actual measurement datapoints and display the modulus distribution as a heatmap.
Poster Number 28
EXPERIMENTAL DETERMINATION OF THE EFFECTIVE INDENTER SHAPE AND EPSILON FACTOR FOR NANOINDENTATION
B. Merle, Department of Materials Science and Engineering, Institute I, University Erlangen-Nürnberg, Germany
V. Maier, Department of Materials Science and Engineering, Institute I, University Erlangen-Nürnberg, Germany
M. Göken, Department of Materials Science and Engineering, Institute I, University Erlangen-Nürnberg, Germany
K. Durst, Department of Materials Science and Engineering, Institute I, University Erlangen-Nürnberg, Germany
The Oliver and Pharr method for evaluating nanoindentation curves is based on the measurement of the contact stiffness, which is usually determined at the very beginning of the unloading sequence, or, using dynamic nanoindentation, continuously throughout the whole loading sequence. A new experimental method was developed in order to keep monitoring the contact stiffness during unloading. It is shown that the new stiffness data allows a direct measurement of the shape of the effective indenter, as previously introduced by Pharr and Bolshakov. Besides, it can be used to predict the shape of the residual impression. This virtually eliminates the need for imaging for the calculation of the equivalent Vickers hardness, based on the residual area. The new method was applied to indentation on fused silica, sapphire, nanocrystalline nickel, and ultrafine-grained aluminum samples. For fused silica, the loading stiffness overlaps quite substantially with the unloading stiffness. This is caused by the extensive elastic recovery found for fused silica, which also leads to a partial reformation of the contacted surfaces after unloading. The effective indenter resembles for fused silica the real indenter geometry. The other materials exhibit a more plastic behavior, so that the loading and unloading contact stiffness overlap only very partially. For comparison, the contact stiffness was also calculated from the load-displacement curve and a very close agreement is found between the new method and the prediction from the Pharr-Bolshakov theory. Last, with the new theory, the epsilon factor is determined experimentally for indentations on fused silica, leading to a value of 0.76, which is in very close agreement with the literature.
Poster Number 29
FATIGUE TESTING OF GOLD THIN FILMS WITH THE BULGE TEST
B. Merle, Department of Materials Science and Engineering, Institute I, University Erlangen-Nürnberg, Germany
M. Göken, Department of Materials Science and Engineering, Institute I, University Erlangen-Nürnberg, Germany
A bulge test setup was used for the fatigue testing of gold thin films in the thickness range 150 – 400 nm. The cyclic loading was performed by varying the pressure of the nitrogen gas under the membranes at a rate of 0.2 Hz. The gas pressure and membrane deflection were recorded continuously during the experiment. Using the conventional plane-strain bulge test theory, it was possible to determine the stress-strain state of the film at every moment, and to calculate for each cycle the residual stress as well as the elastic modulus of the membrane. Two kinds of gold films were tested: purely freestanding films and films attached to a silicon nitride layer. By nature, freestanding films are only subjected to tensile stresses during bulging. The films were fatigued at a pressure amplitude of ~50 kPa, leading to the failure of the membranes after ~ 30 000 cycles. Some clear trends were evidenced during the fatigue test. First of all, the residual stress of the membranes continuously shifted from an initially tensile state towards increasingly compressive values. This resulted in the initially flat membranes buckling after the load was removed. Second, the calculated elastic modulus slightly decreased toward the end of the test, possibly hinting at crack growth affecting the membrane stiffness. When attached to a thick silicon nitride films, the gold layers could be alternatively brought into tension and compression. Due to the presence of the substrate, no membrane failure was observed, even after 100 000 cycles with the maximum pressure amplitude of 100 kPa allowed by the bulge test setup. However, just like with freestanding films, the residual stress of the films grew toward increasingly compressive stresses during the whole test. AFM also evidenced a strong modification of the surface, with the formation of relatively large structures, during the fatigue test. Further examinations with SEM/FIB are under way to determine if grain growth occured.
Poster Number 30
MICRO-SHEAR DEFORMATION OF FCC CRYSTALS
Jenna-Kathrin Heyer, Institute for Materials, Ruhr-Universität Bochum Universitätsstr. 150, Bochum, 44780, Germany
T: +49 234 32 29159, F: +49 234 32 14235, [email protected] Janine Pfetzing-Micklich, Institute for Materials, Ruhr-Universität Bochum
Steffen Brinckmann, Interdisciplinary Center for Advanced Materials Simulation (ICAMS), Ruhr Universität Bochum
Alexander Hartmaier, Interdisciplinary Center for Advanced Materials Simulation (ICAMS), Ruhr Universität Bochum
Gunther Eggeler, Institute for Materials, Ruhr-Universität Bochum
In many areas of technology, micro- and nanosystems gain more and more importance. Based on the fact that the mechanical behavior of micro-scale components discriminates from well-known macroscopic characteristics, new test methods and sample geometries are required. In the last years uniaxial compression tests of micro-pillars, bending of micro-beams and micro-tensile tests were performed to study the mechanical behavior of small-scale samples. One disadvantage of these test methods is the challenging interpretation of the results concerning fundamental deformation mechanisms. Due to a superposition of uniaxial and shear stresses a multitude of slip systems are activated and basic plastic behavior (e.g. determination of the critical shear stress for activating a specific slip system) can not be identified. In the present study, we introduce a new micro-shear experiment using a double shear specimen to directly activate specific slip systems in fcc crystals. The slip systems are identified using electron back scatter diffraction (EBSD) and subsequently the micro-shear specimen is manufactured by focused ion beam (FIB). Deformation of the micro-sample is performed using a nanoindentation system and the microstructural changes are investigated by transmission and scanning electron microscopy (TEM, SEM) before and after deformation to characterize the local deformation and the elementary mechanisms. Load-displacement data allow the identification of critical shear-stresses for activating single slip systems. The new micro-shear test helps to understand fundamentals of plastic behavior which is of basic importance not only for micro- and nanotechnologies, but for all length scales.
Poster Number 31
HEAT- AND EROSION-RESISTANT NANOSTRUCTURED COATINGS FOR THE COMPRESSOR BLADES OF GAS TURBINE ENGINES
Aleksandrs Urbahs, Konstantins Savkovs, Riga Technical University Kalku 1, Riga, LV-1658, Latvia
The increase of gas turbine engine effectiveness is related to the growth of parameters of their gas-dynamic cycle and, first of all, to the growth of gas turbine entry temperature and compressor pressure ratio.
This work analyses the characteristics of functional coatings created by vacuum ion-plasma deposition. These coatings represent double- and triple-layer multi-phase multi-component structures, which are made by condensation of aluminum and titanium according to the given technology. The thickness of coatings is 20…40 µm. They were deposited on compressor blades and vanes manufactured from titanium alloy and chrome-nickel steel. In order to provide the necessary coating properties, the spraying was carried out in argon and nitrogen medium. During the first stage of the research, the analysis of microstructure and microhardness distribution was carried out. It gave the opportunity to confirm the qualities and structure of the coating. In particular, the microhardness of coating external layer exceeded 10 000 MPa, which provides high erosion resistance of a coating.
Then the comparative heat resistance tests for compressor blades and vanes with and without the given coating were carried out. The tests were carried out under the temperature of 780 0Ñ and up to the moment when first symptoms of blade surface destruction occurred, i.e. when corrosion products started to separate. These tests showed, for instance, that the time, during which the first symptoms of coated blade surface destruction occur, increases by 2…3 times when compared with blades without the coating. The test data make it possible to assert that the developed coatings can be used for a long time under the temperatures of 600…750 0Ñ.
Poster Number 32
EXPERIMENTAL INVESTIGATION OF PHYSICO-MECHANICAL PROPERTIES NANOSTRUCTURED ION-PLASMA COATINGS
The work considers different testing methods and facilities used by the author for the evaluation of physico-mechanical properties of materials and parts with wear-resistant coatings. The work considers the technological characteristics of creating coatings using the methods of ion-plasma sputtering and ion implantation. It analyses the results received during experimental investigation of microstructure and chemical composition of the obtained coatings by using a scanning electron microscope with microanalyzer.
It substantiates the modes of testing and proposes criteria for the evaluation of coating wear resistance. It is suggested to carry out abrasiveness tests by using cylindrical rotating specimens made of the material being tested and sample plated specimens. The abrasiveness of a coated plunger is defined from average linear wear of specimens during a certain friction path. It is suggested to carry out the evaluation of wear resistance of restored parts from the results of comparative fast test which defines relations between the wear rates of the restored surface and the sample surface tested in the same conditions.
Tribological tests have been conducted with the help of an automated tribometer according to “ball and disc” scheme (rotational motion module) and “ball and plate” scheme (reciprocal movement module). The method and microhardness measurement instrumentation considered in this work make it possible to evaluate the quality of basic material and coatings. On the basis of the obtained diagrams of coating plasto-elastic deformation, it is suggested to evaluate the strength of different types of coatings.
Poster Number 33
A METHOD TO ESTIMATE THE CONE INDENTATION HARDNESS OF MATERIALS FROM THEIR RHEOLOGICAL SCHEMES
G. Kermouche, University of Lyon, Ecole Nationale d'Ingénieurs de Saint-Etienne 58 rue Jean Parot, saint-etienne, 42023, France
T: +33-4-77-43-75-31, F: +33-4-77-43-75-39, [email protected] J.L. Loubet, University of Lyon, Ecole Centrale de Lyon
J.M. Bergheau, University of Lyon, Ecole Nationale d'Ingénieurs de Saint-Etienne
In this paper we present a method which allows determining the cone indentation hardness of materials from their rheological modelling. A lot of analytical and approximate solutions have been developed in the past to relate the hardness measured with a sharp tip to the yield stress of metals. Nevertheless, most of these solutions have been established in a specific framework - von Mises plasticity, Berkovich tip, ... - and may lead to non negligible errors if the rheology of the indented material is not adequate. In our opinion, there is an high interest in developing methods which are not restricted to a specific rheology even if they are less accurate than the solutions developed on the basis of extensive finite element calculations. The method proposed here has been developed in this way. It is based on the use of the classical assembly rules of rheological scheme. Its application is very simple and quick. This method is checked by comparing the obtained results with the analytical and approximate solutions developed in the past for different rheology : linear viscoelastic solids, viscoelastic non Newtonian fluid and elastic perfectly plastic solids. In the case of linear viscoelastic solids and non Newtonian viscoelastic fluids, the obtained solution corresponds to the analytical solution in considering a constant indentation strain rate. For elastoplastic solids, the obtained solution is not exact but is accurate enough compared to the experimental uncertainties in instrumented indentation testing. It is also shown that this method gives satisfying results for more complex rheology such as pressure dependent solids. The main advantage of this method is that it offers the possibility to develop new approximate solutions without the extensive use of FEM.
Poster Number 34
LOCAL IDENTIFICATION OF THE STRESS-STRAIN CURVES OF METAL MATERIALS AT A HIGH STRAIN RATE USING REPEATED MICRO-IMPACT TESTING
G. Kermouche, University of Lyon, Ecole Nationale d'Ingénieurs de Saint-Etienne 58 rue Jean Parot, Saint-Etienne, 42023, France
T: +33-4-77-43-75-31, F: +33-4-77-43-75-39, [email protected] F. Grange, University of Lyon, Ecole Nationale d'Ingénieurs de Saint-Etienne
C. Langlade, Université de Technologie de Belfort-Montbéliard
The understanding of the effect of many mechanical processes such as the shot peening process requires the knowledge of the behavior of metal at high strain rate. The identification of this behavior is often performed with the help of Hopkinson's bars devices. Nevertheless the resulting stress-strain curves corresponds to a bulk behavior of the material and thus does not take into account the modification induced by surface preparations or surface treatments. In this paper, we have proposed a method based on local micro-impact testing to identify the stress-strain curves of metals near their surface. More precisely, this method is based on the determination of the best stress-strain curve which allows to reproduce the growth of the residual imprint at each impact for a given impact energy. The advantages of the method developed in this paper lies in it simplicity and its low cost. In the first part, the repeated micro-impact set-up is presented. Then the FEM strategy is detailed and the identification method is developed. In the last part of this paper, an application on AISI1045 and AISI316L steels highlight the great interest of using this method to obtain a better stress-strain curve than those classically used. It points out the need to identify appropriate surface stress-strain curves as long as the behavior of surface is concerned. For instance, it should also concern other manufacturing process such as burnishing or finishing processes.
Poster Number 35
MICRO-TENSILE TEST OF NANO-THICK THIN FILM SPECIMEN FABRICATED BY TRANSFERRING PROCESS
Bongkyun Jang, Korea Institute of Machinery & Materials (KIMM) 156, Gajeongbuk-ro Yuseong-gu, Daejeon, Daejeon, 305-343, Republic of Korea
T: +82-868-7850, F: +82-868-7884, [email protected] Hyun-Ju Choi, Korea Institute of Machinery & Materials (KIMM) Jae-Hyun Kim, Korea Institute of Machinery & Materials (KIMM) Hak-Joo Lee, Korea Institute of Machinery & Materials (KIMM)
Measurement of mechanical properties of thin films with nano-sized thickness has been a significant issue in design and reliability evaluation of flexible devices and MEMS devices. Transferring process is a promising technique for fabricating high-performance flexible devices, and is attracting a lot of interest from industry and academia. The transferring process is a mechanical process which can induce stress in transferred devices during process, and the mechanical damage of the transferred devices has been a major concern in this field. For the accurate evaluation of the mechanical behavior of micro/nano scale specimens, the specimens should be freestanding without any interaction with a substrate. Another advantage of the transferring process is its ability to make freestanding structure with ease. In this study, we developed a sophisticated transferring process to make a freestanding specimen with nano-scale thickness, and to align it to a loading direction. The process for making the freestanding specimens is an original process based on a motorized transferring machine and a patterned PDMS stamp. Using the transferring process, single crystal silicon specimens with thicknesses of 200 nm and 100 nm were fabricated and their mechanical properties were measured using a highly-accurate micro-tensile tester with optical capability of strain measurement. The measured properties of the single crystal silicon thin film were compared with the known properties of the bulk single crystal silicon. The mechanical damage occurred during the transferring process was discussed based on the measured tensile test results. This testing technique will open a new methodology for charactering the transferring process and the thin film specimens.
Poster Number 36
STRAIN RATE SENSITIVITY EFFECTS ON THE FAILURE OF METAL FILMS ON COMPLIANT SUBSTRATES
Megan J. Cordill, Erich Schmid Institute of Materials Science, Austrian Academy of Sciences Jahnstrasse 12, Leoben, Steiermark, 8700, Austria
Polymer substrates are used in a variety of new technically advanced flexible electronics and sensors where the devices flex and stretch. Mechanical properties and interfacial phenomena of thin films on compliant substrates are important to understand in order to design reliable flexible electronic devices. These responses are commonly measured in the literature with little discussion of the viscoelastic behavior and strain rate sensitivity of the polymer substrate. Using an in situ tensile device inside a scanning electron microscope the effects of strain rate on the mechanical and interfacial properties are determined. With this technique, the initial fracture and buckling of the film can be observed and correlated to the strain. Thin films of Cr on PET and Cr on PI systems will be examined for their use as adhesion layers. The strain of initial failure and subsequent delamination (buckling) are retarded when slow rates are used, thus increasing the lifetime of the components. Other factors of the polymer substrate, such as crystallite orientation effects of the PET, will also be discussed.
Poster Number 37
ADEQUATENESS OF THE “EFFECTIVELY SHAPED INDENTER” APPROACH FOR THE DETERMINATION OF YIELD STRENGTH
Frank Richter, Chemnitz University of Technology Institute of Physics, 09107 Chemnitz, Germany
T: +4937153138046, F: +4937153121719, [email protected] Andre´ Clausner, Chemnitz University of Technology Kenneth Richter, Chemnitz University of Technology
It was shown that the pressure distribution of a pointed indenter during unloading can be approximated by an “effectively shaped indenter” acting elastically on a flat halfspace [1]. By applying an approach introduced by Schwarzer [2], the concept can be used to evaluate the elastic field of the effectively shaped indenter provided that the elastic-plastic field of the pointed indenter is dominated by its elastic part. If this condition is fulfilled, the spatial maximum of the von Mises stress distribution should deliver the yield strength of the material. Indeed it was found for several bulk [2] and thin film materials [3] that the maximum von Mises stress did agree very well with the yield strength determined using alternative methods. On the other hand, for soft materials (e.g. metals) the concept failed.
In this work, we have investigated a series of standard samples for hardness measurement made of 90 MnCrV8 steel which covered a range of HV 240 – 840 corresponding to E/Y between 65 and 360. Nanoindentation with pile-up correction based on AFM measurements was performed using a Berkovich indenter and the data were evaluated by the procedure given in [2]. Reference values for Young´s modulus and yield strength were obtained utilising surface elastic wave and uniaxial compression tests, resp.. In the region of E/Y from 65 to about 80 the maximum von Mises stress was found to be about twice the reference yield strength. Then the ratio increased, reaching four times the reference yield strength for E/Y = 360. For a borosilicate glass sample (E/Y = 14) the values of maximum von Mises stress and reference yield strength agreed well. We conclude that a sufficiently low E/Y is essential for the applicability of the effectively shaped indenter approach for yield strength determination. Our results indicate that work hardening and similar mechanisms have also to be considered.
[1] G.M. Pharr, A. Bolshakov, J. Mater. Res. 17 (10) (2002 Oct.) 2660. [2] N. Schwarzer, J. Phys., D, Appl. Phys. 37 (2004) 2761. [3] N. Schwarzer, T. Chudoba, F. Richter, Surf. Coat. Technol. 200 (2006) 5566.
Poster Number 38
PREPARATION OF NOVEL POLYIMIDE NANOFOAMS AND INVESTIGATION OF THEIR PHYSICAL AND MECHANICAL PROPERTIES
Elham Aram, Iran Polymer and Petrochemical Institute Iran Polymer and Petrochemical Institute, P.O. Box: 14965/115, Tehran, Iran, Tehran, Tehran,
Shahram Mehdipour-Ataei, Iran Polymer and Petrochemical Institute
Polyimides have attracted much attention as insulating materials in the microelectronic because of their outstanding characteristics such as low dielectric constants, high mechanical properties, good processability and superior thermal stability [1]. The main aim of this research was preparation of nanofoams with low dielectric constants. These nanofoams were prepared from graft copolymers consisting of a thermally stable block as the polyimide matrix and a thermally labile material as dispersed phase. For the preparation of these polyimides, suitable diamines with specific structures were prepared. Reaction of these diamines with aromatic dianhydrides (PMDA, BTDA, and 6-FDA) resulted in preparation of related poly(amic acid) solutions. The functionalized poly(propylene glycol), as labile block, was prepared via reaction of poly(propylene glycol) mono butyl ether with 2-bromo acetyl bromide which then was reacted with poly(amic acid) solutions to prepare grafted copolymers( PAAE-g-PPG). The copolymers were subjected to two thermal cycles for preparation of polyimides and related foams. The copolymers were subjected to two thermal cycles for preparation of polyimides and related foams. In this way, polymer solutions were heated at 180˚C for 6 hr under nitrogen atmosphere for effective removal of solvent and subsequent imidization, and then the polyimides were heated at 300 ˚C for 9 hr under air atmosphere [2]. Upon this thermal treatment, the labile block was subsequently decomposed, leaving pores with size and shape of original copolymer morphology. For comparison, related polyimides without labile group and nanostructure were also prepared. The polyimides and their foams were characterized by some conventional methods including mechanical tests, FT-IR, DSC, DMTA, TGA, SEM, TEM and dielectric constant. The pores were closed-cell and the average size was in the range of 4-40 nm. Due to the contribution of nano pores in the structure of polyimides, the integrity of polyimide structures and therefore the main physical and mechanical properties including tensile strength, modulus, and elongation at break were remained while the dielectric constant of nanofoams were smaller than related polyimides due to the incorporation of pores into final structures. Therefore, nanofoams with lower dielectric constant for application in electronic industry were obtained. References: 1) S. Mehdipour-Ataei, S. Saidi, Polym. Adv. Tech. 2008, 19: 889. 2) S. Mehdipour-Ataei, F. Taremi, J Appl Polym Sci. 2011, 121: 299.
Poster Number 39
DIRECT MEASUREMENT OF CONTACT AREA DURING SPHERICAL INDENTATION OF VISCOELASTIC POLYMERS
Andy Bushby, Queen Mary University of London Mile End Road, London, E1 4NS, UK
T: +44 20 7882 5276, F: +44 20 7882 3390, [email protected] Tanya Ekers, Queen Mary University of London
Polymer coatings are widely used in many industrial applications such as coatings on car bodies and refrigerators, and as varnishes on floor coverings and wood. As protective coverings polymer coatings are subject to wear and degradation making their mechanical properties a key performance indicator. Mechanical properties of non-polymeric coatings can be successfully determined using nanoindentation (ISO 14577). However, nanoindentation of polymers often results in elastic moduli significantly higher than those of tensile testing or dynamic mechanical analysis (van Landingham 2003, Oyen 2007). Established approaches to indentation measurement, such as the Oliver and Pharr analysis, dynamic indentation and creep compliance, all rely on contact areas calculated from displacement measurements via Hertzian mechanics. Here we present experiments to directly determine the contact area simultaneously with load and displacement measurements during macro-scale indentation of transparent bulk polymers, via an in situ optical system. Commercially available PMMA and Epoxy resin with two different cross-link densities were investigated. The system was calibrated and verified using soda-lime glass. This novel approach suggested that for some polymers spherical indentation can be non-Hertzian. The results calculated from nanoindentation, macro-instrumented-indentation and creep compliance were compared. It appeared that the ramp load times as well as surface properties contribute to the non-Hertzian contact. The results imply that it may not be feasible to characterise the mechanical response of polymeric, viscoelastic materials from a single indentation test but that a series of tests under different loading conditions may be required.
Poster Number 40
DETERMINING REAL INDENTER GEOMETRY IN SPHERICAL NANOINDENTATION TAKING INTO ACCOUNT INFINITESIMAL DEFORMATION OF THE INDENTER
Seung-Kyun Kang, Seoul National University Bd. 131-302, Dept. of Materials Science & Eng., Seoul National University, Sillim9-dong, Gwanak-gu,
Seoul, Seoul, 151-744, Korea T: +82-2-880-8404, F: +82-2-886-4847, [email protected]
Young-Cheon Kim, Seoul National University Jong-Heon Kim, Seoul National University Won-Seok Song, Seoul National University
Dongil Kwon, Seoul National University
A spherical indenter that is not geometrically self-similar, unlike the Berkovich and conical indenters, can be used to evaluate the load and displacement curve reflecting the depth-dependent stress and strain relation beneath an indenter. This feature makes it possible to predict mechanical properties such as yield strength, strain-hardening exponent, and so on from simple indentation testing. However, use of this technique in the nanoscale range is limited because of the difficulty of manufacturing a reliable indenter. Improved manufacturing techniques have made it possible to produce advanced spherical indenters by blunting sharp indenters, but determining a way to calibrate the real shape of the spherical indenter remains an issue. This paper compares two different methodologies for indenter calibration: one uses the Hertz equation in the elastic contact region, the other uses AFM to observe the residual impression at the plastic contact. We found a large mismatch in effective radius between the two methods. We adopt a functional frame compliance that is calculated from the concept of infinitesimal indenter deformation. After correcting for the displacement with functional frame compliance in the elastic contact region, we obtain from the Hertz equation an effective radius that corresponds to the impression method.
Poster Number 41
NANOINDENTATION TESTING OF TI6AL4V NANOLAYERS MODIFIED BY ION BEAM METHODS
F. Cerny, CTU in Prague Technicka 4, Prague, 16607, Czech Republic
T: +420 224352437, F: +420 224310292, [email protected] J. Sepitka, V. Jech, P. Vlcak, T. Horazdovsky, S. Konvickova, CTU in Prague
The titanium alloy Ti6Al4V is used mainly in aircraft industry and in biomedical engineering (e.g. for joint replacements and dental bioimplants). In biomedical engineering the titanium alloy is used especially for its good biocompatibility. But for use in this branch the surface properties of titanium based bioimplants are not fully satisfactory and they must be modified. Several methods for the modification of bioimplants can be applied. In our work we applied ion beam methods for the modification of elastic modulus and nanohardness of surface nanolayers of the titanium alloy Ti6Al4V.
The cleaned one side polished flat Ti6Al4V alloy samples were divided into three groups for application of three main kinds of ion beam methods: ion implantation of nitrogen, ion beam mixing of carbon and ion beam mixing of boron. The ion implantation of nitrogen proceeded with ion energy of 90 keV and with four different values of fluence. The ion beam mixing of carbon was carried out with two values of thickness of electron beam evaporated carbon nanolayer and two values of fluence of irradiating nitrogen ions for mixing of carbon atoms. The ion beam mixing of boron was carried out also with two values of thickness of electron beam evaporated boron nanolayer but only with one value of fluence of irradiating nitrogen ions for mixing of boron atoms. The elastic modulus and nanohardness of resulted ion beam modified surface nanolayers were investigated by nanoindentation testing. The dependence of the reduced elastic modulus and the nanohardness on the depth was registered. The maximal registered values of nanohardness were 22 GPa in the case of ion implantation of nitrogen, 15 GPa in the case of ion beam mixing of boron and 13 GPa in the case of ion beam mixing of carbon.
Poster Number 42
INFLUENCE OF PRE-EXISTING DISLOCATIONS ON THE POP-IN PHENOMENON DURING NANOINDENTATION IN MGO
C. Tromas, Institut P’, UPR 3346 CNRS – Université de Poitiers – ENSMA Département de Physique et Mécanique des Matériaux
Bât. SP2MI, Bd. Pierre et Marie Curie, BP 30179, Futuroscope Chasseneuil Cedex, 86962, France T: 0033549496724, F: 0033549496692, [email protected]
A. Montagne, V. Audurier, Institut P’, UPR 3346 CNRS – Université de Poitiers – ENSMA Département de Physique et Mécanique des Matériaux
In this study, the influence of pre-existing dislocations on the pop-in phenomenon has been investigated in MgO single crystals, in terms of individual dislocations.
A controlled density of dislocations has been introduced by cleavage in MgO single crystals, prior to indentation. The dislocation density is indeed related to the cleavage rate [1]. Furthermore, all the dislocations introduced by cleavage are half loops, emerging on the cleaved surface and lying in {110}45 planes [2]. The dislocation density has been then characterized by nanoetching, that is by observing by atomic force microscopy (AFM) the nanometre size etch pits produced by chemical etching at the emergence points of the dislocations. Moreover, in certain conditions, the shape of the etch pits can also indicate the slip plane associated to the dislocations.
In a first step, the pop-in load has been studied as a function of the pre-existing dislocation density, when indenting with a spherical indenter of 9.5 µm radius of curvature. It has been observed that the pop-in load strongly decreases when the pre-existing dislocation density increases. Then, the double etching technique has been used to investigate the role played by the pre-existing dislocations in the dislocation nucleation process during the pop-in. By etching the sample before and after indentation, it is indeed possible to identify, in a same AFM observation, the initial and final positions of the pre-existing dislocations around an indent, as well as the specific dislocations nucleated during the pop-in. Successive polishing and etching have then allowed to precise the dislocation structure in 3D in the indented areas.
It is shown that the nucleation site of new dislocations during the pop-in is not directly correlated to the pre-existing one. The position of the new dislocations is indeed coherent with a nucleation located at the maximum resolved shear stress during the pop-in. Thus, the activation of Frank-Read sources on the pre-existing dislocations cannot explain the effect of pre-existing dislocations on the pop-in load.
[1] J. J. Gilman, « Nucleation of dislocation loops by cracks in crystals », Journal of Metals, vol. 212, no. 310, p. 449-454, 1957. [2] J. L. Robins, T. N. Rhodin, et R. L. Gerlach, « Dislocation Structures in Cleaved Magnesium Oxide », Journal of Applied Physics, vol. 37, no. 10, p. 3893, 1966.
Poster Number 43
FRACTURE TESTING – FROM THE MICROSCALE TO MACROSCALE
David E.J. Armstrong, University of Oxford, Department of Materials Parks Road, Oxford, OX1 4PH, United Kingdom
T: 0441865273768, F: +44 (0)1865 273789, [email protected] J. Gibson, University of Oxford, Department of Materials
A.J. Wilkinson, University of Oxford, Department of Materials S.G. Roberts, University of Oxford, Department of Materials
Fracture, especially brittle fracture, is often controlled by grain boundary behaviour. Until now measuring the fracture properties of single grain boundaries has required macroscopic bi-crystals which are expensive and may only be available in special orientations (if at all) . We have developed a technique using micro-cantilevers, manufactured using focussed ion beam machining and mechanically tested using a nanoindenter. At the small length-scale the balance between fracture and plasticity is altered so that quantitative analysis is limited to very brittle materials. We have used the method to measure the fracture toughness of selected grain boundaries of a wide range of types in bismuth-embrittled copper, characterised using EBSD and TEM-EDX. The results show measured fracture toughness values between 1 and 7 MPam0.5. This is in good agreement with the literature values, however no systematic dependence on crystallography, either in fracture plane of the boundaries or mis-orientation, was seen. Previous work on Cu-Bi bi-crystals has focused on “special” low sigma boundaries and this is the first time a large number of non-special boundaries have been tested.
The technique has also been applied to tungsten and tungsten 5wt% tantalum alloys for use in nuclear fusion applications. Four point bend tests have been performed on millimetre-scale specimens of W 5wt%Ta alloy, at temperatures from 290K to 1273K. Tests at temperatures up to 600K were seen to fracture in a brittle manner at a maximum longitudinal stress of approximately 700MPa; however the fracture plane tends to follow a path along the long axis of the bar, rather than straight through as seen in pure W alloys. EBSD shows that the path follows specific grain boundaries, which are weaker than the majority of the grain boundaries and the grain interiors. At temperatures above 600K the fracture mode changes from purely brittle to a mixed mode, with a yield stress of 1GPa and failure stress of 1.1GPa. Failure occurs by delamination of the specimen along the same types of boundaries as those seen to fail in a brittle manner at lower temperatures. Micro-mechanical testing of FIB machined cantilevers has been used to study the difference in fracture toughness of single boundaries in this alloy. It is found the fracture toughness varies from 1-20 MPam0.5 depending on the type of boundary tested. It is found the boundaries with the lowest fracture toughness , are those which dominate the fracture properties in the macroscale tests.
Poster Number 44
MICRO-CANTILEVER TESTS OF STRENGTHENING FROM ALPHA/ALPHA AND ALPHA/BETA BOUNDARIES IN TITANIUM ALLOYS
Jicheng Gong, University of Oxford Parks Road, Oxford, Oxon, OX1 3PH, UK
T: +1865 273792, F: +1865 273764, [email protected] Angus J Wilkinson, University of Oxford
Three titanium alloys pure á Ti-6Al, near á Ti-6Al-4V, and â stabilized Ti-15Mo were selected as representative systems to investigate micromechanics of individual, bi and multiple grain/phase boundaries. Following EBSD surveying of large grained polycrystals focused ion beam was used to fabricate single, bi-crystal and multicrystalline microcantilevers that were then tested in bending using a nanoindenter The standard geometry of our microcantilevers is 30 µm long, 5 µm wide, and the cross section is equilateral triangle. The shear stress for plastic flow is extracted by fitting a crystal plasticity finite element simulation to the measured load-displacement response.
á/â lamellar (Ti-6Al-4V): Ti-6Al-4V was processed to have a relatively fine á(~1 µm)+â(~0.1 µm) lamellar microstructure. Many orientations were tested to examine the effect on the flow stress of the misalignment of slip systems across the á/â interfaces. The results show that the strengthening relative to single phase á Ti-6Al for slip on the prismatic planes increases with misalignment from the nearly aligned (~0.7 degs) a1 to the fairly well aligned (~12 degs) a2 to the misaligned a3 system. A similar increase in strength was seen for slip on the basal planes.
Individual á/â boundaries (Ti-15Mo): Ti-15Mo was heat treated to produce a coarse á+â lamellar microstructure, with á lathes ranging from 1 to 7 µm wide. This allows fabricationof á/â bi crystal and â/á/â tri crystal microcantilevers. The results show that the strength of bi-crystal beams is higher than single crystal ones that were prepared in the adjacent á and â crystals; and the tri-crystals are stronger still.
Individual á-á boundaries: Microcantilevers were prepared across á-á grain boundaries in Ti 6Al. The pattern of slip features on the surfaces of tested beams indicate strong interaction between the deforming grains. In most cases, the strength of such bi-crystal beams was between that of single crystal ones prepared from the two adjacent grains at the same orientations.
Poster Number 45
NANOINDENTATION STUDY OF HOMO-EPITAXIED 4H-SIC SINGLE CRYSTALS: THE EFFECT OF DOPING
J. Rabier, Département Physique et Mécanique des Matériaux Institut P’, UPR 3346 CNRS - Université de Poitiers - ENSMA
A. Amer, Département Physique et Mécanique des Matériaux Institut P’, UPR 3346 CNRS - Université de Poitiers - ENSMA
J.L. Demenet, Département Physique et Mécanique des Matériaux Institut P’, UPR 3346 CNRS - Université de Poitiers - ENSMA
C. Tromas, Département Physique et Mécanique des Matériaux Institut P’, UPR 3346 CNRS - Université de Poitiers - ENSMA
Electronic effects have been found to impact the mechanical properties of semi conductors. In silicon and GaAs, it is well established that doping acts on dislocation mobility and as a consequence yields to a modification of the brittle-to-ductile transition temperature. As far as silicon carbide is concerned such an effect has not been evidenced yet.
In this context a nanoindentation study has been made on 10 μm thick homo-epitaxied 4H-SiC single crystals on the basal plane: intrinsic (Ni≈ 6.1013 cm-3), n-type (N, Nn ≈ 8.1017 cm-3) and p-type (Al, Np ≈ 4.1017 cm-3). Experiments were performed at room temperature using a spherical indentor and Transmission Electron Microscopy (TEM) observations of the indentation sites were conducted in order to obtain information on the deformation mechanisms.
A statistical analysis of the measurements of pop-in load levels clearly reveals different behaviours as a function of electronic doping: the pop-in level is somehow the same for intrinsic and n type materials whereas it is significantly larger for the p type material. Since the stress field is known for a spherical indentor, this allowed determining the stress associated to this incipient plasticity event which is though to be relevant to dislocation nucleation: 40±8GPa for intrinsic, 41±9 GPa for n type, 53±11 GPa for p type. This demonstrates clearly that doping can also impact dislocation nucleation.
The dislocation features located close to the imprints show a different extension as a function of doping. However, in the different type of materials, the deformation microstructures consist in perfect dislocations with Burgers vectors located in (0001). Although the stacking fault energy is very low in 4H-SiC, this shows that the nucleation at high stresses of dislocation with a compact core has to be considered as a quite general mechanism in semi conductor materials.
Poster Number 46
EFFECT OF IN SITU HYDROGEN CHARGING ON THE PULSED PLASMA NITIDING LAYER IN STAINLESS STEELS
Masoud Asgari, Department of Engineering Design and Materia,Norwegian University of Science and Technologyls
Richard Birkelands vei 2b, Trondheim, 7491, Norway T: 004746242309, F: 004773593807, [email protected]
A. Barnoush, Saarland University, Saarbrucken, Germany R. Johnsen, Norwegian University of Science and Technology, Trondheim, Norway
R. Hoel, MOTecH Plasma Company, Oslo, Norway
In many subsea components, the use of stainless steel alloys has been increased. But hydrogen entrapment resulting from external cathodic protection, combined with a certain stress/strain level, may cause atomic hydrogen to enter into the alloy and reduce the mechanical strength. Such an effect may destroy the integrity of equipment or a system. Pulsed plasma treatment (ppn) may be a possible way to reduce the hydrogen intake. Such a surface treatment will also reduce the wear and galling of components.
In this work nitrided layers on stainless steels were examined by means of a nanoindention method at different loads. Additionally, in situ electrochemical nanoindentation technique was used to electrochemically charge the samples in situ and investigates the effect of hydrogen on mechanical properties. In this method changes in the plasticity and in the hardness due to the absorption of atomic hydrogen has been traced. and in addition effect of PPN on the sub micro structure has been investigated with Electron backscatter diffraction method.
Poster Number 47
DIRECT EVALUATION OF DISLOCATION NETWORKS AND DISLOCATION DENSITY TENSORS FROM ATOMISTIC DATA
Christoph Begau, Interdisciplinary Centre for Advanced Materials Simulation (ICAMS), Ruhr-University Bochum
Jun Hua, Department of Mechanics, Xi’an University of Architecture and Technology, China Alexander Hartmaier, Interdisciplinary Centre for Advanced Materials Simulation (ICAMS), Ruhr-
University Bochum, Germany
Plasticity caused by the nucleation and interaction of dislocations is an important aspect in crystal deformation. Molecular dynamics simulations offer the possibility to study deformation mechanisms on an atomistic scale without assumptions on strain gradient effects, but require sophisticated analysis routines in order to deal with the large amount of data generated. A new efficient approach to analyze atomistic data on-the-fly during the simulation is introduced, allowing identification of the dislocation network including their Burgers vectors in high temporal resolution. This data not only provides the evolution of dislocations over time, but enables to quantify dislocation density tensors in three dimensional volume elements with an edge length down to 2 nm. Lattice rotation patterns on an atomic level offer additional information concerning crystal deformation. We have applied these methods in simulations of nanoindentation in single crystal copper and compared the results with experimental data.
The presented approach provides useful insight into deformation mechanisms during plastic deformation and can extract valuable information to bridge simulations on atomic levels and continuum description. Furthermore the methods are easily adaptable to different crystal structures. Besides face centered cubic metals, it has been successfully applied in body centered cubic metals (Fe, W) and multiphase material like austenitic-martensitic shape-memory-alloys.
Poster Number 48
ONSET OF PLASTICITY IN SILICON NANOWIRES
Julien Godet, Institut Pprime - CNRS - Université de Poitiers - ENSMA SP2MI - BP 30179 - Futuroscope, Poitiers, 86962, France
Since it is possible to control the growth of nanowires and to manipulate these structures, the mechanical tests have revealed very high elastic strength compare to their bulk counterparts. This feature can be attributed to a size effect: at very small size the number of dislocation sources in bulk strongly decreases and they can even disappear! Secondary sources usually located on the surfaces are then activated, but at much larger stresses than those currently observed in bulk.
The physical properties like electron mobility, gap... of such nanostructures sustaining very large strains, can be tuned by only playing on the strain tensor, opening the new technological area of the strain material engineering. A nice example is the strain-silicon technology present in most of the processors manufactured today. However the ageing of such devices can relax the accumulated strain by dislocation mediated plasticity leading to strong modification of the electronic properties, like the damaging effects on charge carriers life-time and mobility. A deep understanding of the onset of plasticity is then unavoidable to predict the evolution of such nanostructures under high strain.
In this study, we focus on the role of surfaces on the onset of dislocation nucleation in semiconductor nanowires. We have used molecular dynamics simulations to access to the atomic mechanisms at the origin of plasticity, and chosen silicon as a model of semiconductors. We have considered nanowires with various orientations and surfaces. In our simulations, we have observed the activation of different modes of plasticity, among which an unexpected slip mechanism in {110} planes - identified as an indirect consequence of the low dimensions of the nanostructures. In addition, we have shown a strong competitiveness between the surfaces and the corners of nanowires for the dislocation nucleation, in particular when surface steps are parallel to the glide planes of dislocations. Finally our results show that the engineering of surfaces and corners are crucial to control the onset of plasticity in nanostructures and suggest that this control could be even larger in more complex structures like core-shell systems with amorphous, hydrogen or oxide layers.
Poster Number 49
DEFORMATION ANALYSIS OF VERTICALLY ALIGNED CARBON NANOTUBE BUNDLES UNDER UNIAXIAL COMPRESSION
Shelby B Hutchens, California Institute of Technology 1200 E California Blvd. MC 309-81, Pasadena, CA, 91125, USA
T: 16263954416, F: 16263958868, [email protected] Alan Needleman, University of North Texas
Lee J Hall, Jet Propulsion Laboratory Julia R. Greer, California Institute of Technology
Vertically aligned carbon nanotubes (VACNTs) serve as integral components in a variety of applications including MEMS devices, energy absorbing materials, dry adhesives, light absorbing coatings, and electron emitters, all of which require structural robustness. Understanding of the VACNT structures’ mechanical properties and constitutive stress-strain relationship is central to the rational design of many of these applications. We describe the results of in situ uniaxial compression experiments of 50 micron diameter cylindrical bundles of these complex, hierarchical materials as they undergo unusual deformation behavior. Most notably they deform via a series of localized folding events, originating near the bundle base, which propagate laterally and collapse sequentially from bottom to top. This deformation mechanism accompanies an overall foam-like stress-strain response having elastic, plateau, and densification regimes with the addition of undulations in the stress throughout the plateau regime that correspond to the sequential folding events. Microstructural observations indicate the presence of a strength gradient, due to a gradient in both tube density and alignment along the bundle height, which plays a key role in both the sequential deformation process and the overall stress-strain response. We capture the sequential buckling phenomena and strength gradient effect through application of a finite element model based on a viscoplastic solid in which the flow stress relation contains an initial peak, followed by strong softening and successive hardening. Through this combination of experimental and modeling approaches, we discuss the particular mechanisms governing non-trivial energy absorption via the sequential formation of localized buckles in the VACNT bundles.
Poster Number 50
MICROMECHANICAL TESTING OF STRESS CORROSION CRACKING BEHAVIOUR AT INDIVIDUAL GRAIN BOUNDARIES IN STAINLESS STEEL
Alisa Stratulat, University of Oxford Parks Road, Oxford, Oxfordshire, OX1 3PH, UK
T: 01865 283326, F: N/A, [email protected] S.G. Roberts, University of Oxford T.J. Marrow, University of Oxford
Stress Corrosion Cracking (SCC) involves a highly complex interplay of diffusional, chemical and mechanical factors in a series of related mechanisms, and affects material performance in a wide range of materials systems and environments. Within the nuclear industry where safety and structural integrity are crucial concerns SCC is of great significance; in particular in some Ni based alloys, and austenitic stainless steels. In such systems SCC is predominantly along grain boundary paths. While it is clear that some grain boundaries are more resistant to crack growth than others (in particular Σ3 boundaries offer increased resistance to the crack advance), quantitative information concerning crack growth rates on different grain boundary types is currently unavailable. Such information would be invaluable in developing mechanistic understanding of SCC and is required for further development of microstructurally based fracture mechanics models of SCC through polycrystals. This presentation will describe a method recently developed to investigate SCC crack growth rates of individual grain boundaries in a model system: sensitised 304 stainless steel in potassium tetrathionate environment.
Focussed ion beam (FIB) facilities were used to machine small, 5 µm wide by 25 µm long cantilever beams at selected sites in the steel. The cantilevers were cut so that the beam contained, close to the built-in end, a selected grain boundary, characterised by EBSD. Specimens were mounted in a small vessel containing potassium tetrathionate solution, and then cantilevers were loaded at the free end using a nanoindenter. Changes in beam compliance were used to follow the increase of the crack length with time, and hence determine the crack growth rate / applied stress intensity relation for cracks in grain boundaries of different character.
Poster Number 51
INVESTIGATION OF THE SIZE DEPENDENT MECHANICAL BEHAVIOR OF α-FE AND NON-ALLOYED DC04 STEEL
Simone Schendel, Karlsruhe Institute of Technology, Institute for Applied Materials Hermann-von-Helmholtz-Platz 1, Eggenstein-Leopoldshafen, BW, 76344, Germany
T: +49 721 608-25858, F: +49 721 608-22347, [email protected] Reiner Mönig, Karlsruhe Institute of Technology, Institute for Applied Materials Oliver Kraft, Karlsruhe Institute of Technology, Institute for Applied Materials
Iron and steel are materials of great technological importance. Many steels have complex microstructures that contain grains and phases with small dimensions. Since the mechanical behavior of the steel as a bulk material may be affected by the mechanical behavior of these small elements, knowledge of their size dependent mechanical properties is important. In this work, a first step in this direction was taken by investigating the two very basic micro-structural constituents which are α-Fe and a simple ferritic steel containing low concentrations of C and metallic impurities. This steel is known as DC04 steel and technologically used as a deep drawing steel. Both, α-Fe and DC04 were mechanically tested using the micro-compression technique. In experiments on single crystalline pillars, the size dependent mechanical behavior was investigated with a focus on the effect of alloying elements and the role and predeformation. In order to observe the effect of grain boundaries in the deformation process, large polycrystalline pillars with diameters of 22µm were produced by electrical discharge machining and subsequent FIB milling. In the pillars, the active glide systems were determined by a combination of deformation morphology and EBSD data. The results show that the presence of predeformation strongly affects the size dependence. For the mechanical behavior of the deep drawing steel, the results indicate that the strength of this steel is not strongly affected by the interaction between dislocations and grain boundaries but instead is controlled by the spacing of precipitates inside the ferritic matrix.
Poster Number 52
EFFECT OF SPECIMEN SIZE ON THE TENSILE STRENGTH OF WC–CO HARD METAL
Thomas Klünsner, Materials Center Leoben Forschung GmbH (MCL) Roseggerstraße 12, Leoben, Styria, 8700, Austria
T: +43 3842 45922 - 33, F: +43 3842 45922 - 5, [email protected] Stefan Wurster, Reinhard Pippan, Erich Schmid Institute of Materials Science of the Austrian Academy of
Sciences Peter Supancic, Institut für Struktur- und Funktionskeramik, Montanuniversität Leoben
Reinhold Ebner, Materials Center Leoben Forschung GmbH (MCL) Johannes Glätzle, Arndt Püschel, Ceratizit Austria Ges.m.b.H.
The fracture behaviour of ultrafine grained WC-Co hard metal was investigated in tensile and bending tests using different specimen sizes and test arrangements in order to study the size effect on the tensile strength, by varying the effectively tested volume over a range of roughly 10 orders of magnitude. Mechanical testing of centimetre sized specimens was performed by means of tensile tests using an hourglass shaped specimen. Millimetre sized specimens were tested in four point and three point bending test setups. Micrometre sized specimens, produced via focused ion beam milling, were loaded in situ in a scanning electron microscope utilizing a piezo-electrically controlled cube corner micro-indenter. Resulting fracture surfaces were examined in order to identify origins of fracture.
The main result of the present work is that strength values are found to increase from about 2500 MPa to about 6000 MPa when the size of the effectively loaded volume is varied from about 100 mm³ to about 1E-8 mm³. This kind of behaviour is typical for brittle materials in which strength is defect controlled and can be explained by a size effect according to Weibull theory.
In case of the micrometre sized specimens, no defects were found on the fracture surfaces. Estimations of critical defect sizes in these specimens based on linear elastic fracture mechanics give values in the order of magnitude of the submicron-sized tungsten carbide particles. It is therefore expected that the high strength values found in these specimens are close to the inherent material strength.
Poster Number 53
OBSERVATION OF DISLOCATION-MOVEMENT IN PASSIVATED AL FILM USING IN SITU TRANSMISSION ELECTRON MICROSCOPY NANOINDENTATION
Ludvig de Knoop, CEMES-CNRS 29 rue Jeanne Marvig, Toulouse, 31055, France
Understanding the mechanical properties of nanomaterials is a subject of major interest in different fields of nanosciences and nanotechnologies. Particularly in microelectronics, metallic thin films used in interconnections are subjected to high current density and consequently high thermal loads. Thermal loads generate stresses. Hence, stress-strain relations and elastic to plastic transitions becomes a critical issue to warrant device integrity.
With the advent of in situ transmission electron microscopy (TEM) nanoindentation, the mechanical behavior of small-scale samples can be investigated at the nanoscale, as plastic behavior can be triggered locally and the associated physical processes followed dynamically in the microscope.
Here, we investigate the plastic behavior of passivated Al thin films. A dedicated TEM sample holder, equipped with an actuator and a diamond mounted on a force-sensing MEMS device, allows indenting cross-sectional specimens fib-milled in a H-bar configuration. Al films of 1 μm thickness are deposited on a Si substrate and covered by a 1 μm thick SiO2 layer. To study the dislocation behavior at the Al/SiO2 interfaces, the upper layer of silica, which is designed to distribute the stress imposed by the indenter and also to function as a protective layer during the fib-milling process, is pressed into the diamond indenter.
Load-unload curves acquired in situ have shown that dislocations tend to move towards the Al/SiO2 interface. The result is compared with in situ thermal cycling of similar samples, where the stress originates from difference in thermal expansion coefficients. To support the discussions, finite element models are built to calculate the transmitted stresses into the Al film by the indentation process, as well as to estimate the thermal stresses in the heating experiments.
Poster Number 54
3D-EXPERIMENTAL STUDY OF THE FORMATION OF SLIP BANDS NEAR BOUNDARIES IN BICRYSTALS WITH SMALL DIMENSIONS
Nousha Kheradmand, Saarland University Saarland University, Department of Materials Science, Bldg. D22 P.O. Box 151150, Saarbruecken,
A quantitative understanding of the interaction between dislocations and grain boundaries is necessary for the micro- and nanomechanical modeling of polycrystals. Experiments on bicrystals are needed for testing the various theoretical models on the different size scales. Microcompression tests combined with molecular dynamic simulations of bicrystalline pillars enable us to investigate the dislocations interaction with a specified GB. Direct observations in Scanning Electron Microscope in combination with the stress-strain curves and subsequent Electron Back Scattered Diffraction (EBSD) measurements were used to find out the fundamental mechanisms. The increase in flow stress of bicrystals shows that the GB is a barrier to the dislocation motion and can be overcome by slip transmission to the neighboring grain. It is observed that lattice rotation takes place by the dislocation pile-up at the grain boundary and facilitates the slip transmission.
Engineering Conferences International Participants List
Nanomechanical Testing in Materials Research and Development Lanzarote, Canary Islands, Spain
10/9/2011 through 10/14/2011
Jorge Alcala Professor Polytechnic University of Catalunya Avda Diagonal 647 Barcelona 08028, Spain Phone: 34-93-401-6287 Fax: 34-93-401-6706 Email: [email protected]
Elham Aram Iran Polymer and Petrochemical Institute P.O. Box 14965/115 Tehran, 1497713115 Iran Phone: 98-21-44-58-0026 Fax: 98-21-44-19-6583 Email: [email protected]
David Armstrong University of Oxford Materials Department Parks Road Oxford, 0X1 4PH United Kingdom Phone: 44-18-65-27-3768 Fax: 44-18-65-27-3789 Email: [email protected]
David Bahr Professor & Director Washington State University Mechanical and Materials Engineering P.O. Box 642920 Pullman, WA 991642920 USA Phone: 1-509-335-8654 Fax: 1-509-335-4662 Email: [email protected]
Etienne Barthel CNRS/Saint-Gobain CNRS/Saint-Gobain BP 135 Aubervilliers, 93303 France Phone: 33-1-4839-5557 Fax: 33-1-4839-5562 Email: [email protected]
Sandrine Bec LTDS / Ecole Centrale De Lyon / CNRS 36 Av Guy De Collongue Batiment H10 Ecully Cedex 69134, France Phone: 33-4-7218-6270 Fax: 33-4-7843-3383 Email: [email protected]
Christoph Begau ICAMS, Ruhr University Bochum Stiepeler Strasse 129 Bochum, 44801 Germany Phone: 49-234-3229-9377 Fax: 49-234-3214-984 Email: [email protected]
Michael Berg European Regional Sales Manager Hysitron, Inc. 10025 Valley View Road Minneapolis, MN 55344 USA Phone: 1-952-835-6366 Fax: 1-952-835-6166 Email: [email protected]
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Steve Bull Newcastle University CEAM Merz Court Newcastle Upon Tyne, NE1 7RU United Kingdom Phone: 44-191-222-7913 Fax: 44-191-222-5292 Email: [email protected]
Andrew Bushby Queen Mary University of London School of Engineering and Materials Science Mile End Road London E1 4NS, United Kingdom Phone: 44-20-7882-5276 Fax: 44-20-7882-3390 Email: [email protected]
Frantisek Cerny Prof. Czech Technical University in Prague Technicka 4 Prague 16607, 16607 Czech Republic Phone: 420-22-43-52-437 Fax: 420-22-43-10-292 Email: [email protected]
Won Chang Korea Institue of Machinery and Materials 171 Jang-dong Yuseong-gu Daegeon, 305-343 South Korea Phone: 82-42-868-7134 Fax: 82-42-868-7884 Email: [email protected]
Anna Charvatova Campbell Czech Metrology Institute Okruzni 31 Brno, 638 00 Czech Republic Phone: 420-5-4555-5337 Fax: 420-5-4555-5183 Email: [email protected]
Olga Chernogorova Leading Researcher Baikov Institute of Metallurgy and Materials Science Leninskii Pr. 49 Moscow, HI 119991 Russia Phone: 7-499-135-7492 Fax: 7-499-135-3215 Email: [email protected]
Andre Clausner Dipl.-Ing. Chemnitz University of Technology Reichenhainerstrasee 70 Chemnitz, Sachsen 09126, Germany Phone: 49-371-5313-6987 Fax: 49-371-5312-1719 Email: [email protected]
William Clegg University of Cambridge Pembroke Street Cambridge, CB2 3QZ United Kingdom Phone: 44-1223-33-4470 Fax: 44-1223-33-4567 Email: [email protected]
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Megan Cordill Montanuniversitat Leoben Materials Physics Department Jahnstrasse 12 Leoben 8700, Austria Phone: 40-38-4280-4313 Fax: 43-38-4280-4116 Email: [email protected]
Diana Courty ETH Zurich ETH Zurich Nanometallurgy Wolfgang-Pauli-Strasse 10 Zurich, 8093 Switzerland Phone: 41-44-633-6915 Fax: 41-44-632-1101 Email: [email protected]
Bryan Crawford Application Engineer Nanomechanics, Inc. 105 Meco Lane Oak Ridge, TN 37830 USA Phone: 1-864-481-8451 Fax: 1-865-481-8455 Email: [email protected]
Ludvig De Knoop CEMES-CNRS 29 Rue Jeanne Marvig Toulouse, 31055 France Phone: 33-5-62-25-7897 Fax: 33-5-62-25-7999 Email: [email protected]
Gerhard Dehm Professor University of Leoben Jahnstrasse 12 Materials Physics Leoben, Styria 8700, Austria Phone: 43-38-4280-4112 Fax: 43-38-4280-4116 Email: [email protected]
David Dunstan Professor Queen Mary University of London Mile End Road London E1 4NS, United Kingdom Phone: 44-207-882-3687 Fax: 44-208-981-9465 Email: [email protected]
Karsten Durst University Erlangen-Nürnberg Department of Materials Science and Engineering, Institute 1 Martensstrasse 5 Erlangen, Bavaria 91058, Germany Phone: 49-913-1852-7505 Fax: 49-913-1852-7504 Email: [email protected]
Ernest Fantner Managing Director GETec Dechantstrasse 9 Langenlois, A-3550 Austria Phone: 43-664-393-7743 Fax: 43-18-90-43-4590 Email: [email protected]
Marc Fivel SIMaP-GPM2 ENSE3 101 Rue De La Physique BP 46 St Martin D'heres, 38402 France Phone: 33-4-7682-6463 Fax: 33-4-7682-6382 Email: [email protected]
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Mathias Goken University Erlangen-Nurnberg, Institute I Materials Science and Engineering Dept Martensstrasse 5 Erlangen Bavaria, 91058 Germany Phone: 49-9131-852-7501 Fax: 49-9131-852-7504 Email: [email protected]
Jicheng Gong Oxford University Department of Materials Parks Road Oxford, Oxfordshire, 0X1 3PH United Kingdom Phone: 44-18-65-28-3659 Fax: 44-18-65-27-3764 Email: [email protected]
Robert Gralla INM - Leibniz Institute for New Materials Campus D2 2, Saarbrucken Saarbrücken, 66123 Germany Phone: 49-681-9300-372 Fax: Email: [email protected]
Paul Grasske Managing Director Micro Materials Limited Willow House Yale Business Village Ellice Way, Wrexham LL13 7YP United Kingdom Phone: 44-19-7826-1615 Fax: Email: [email protected]
Julia Greer Professor California Institute of Technology 1200 East California Boulevard MC 309-81 Pasadena, CA 91125 USA Phone: 1-626-395-4127 Fax: 1-626-395-8868 Email: [email protected]
Gaylord Guillonneau LTDS Ecole Centrale de Lyon 36 Avenue Guy De Collongues Ecully, 69134 France Phone: 330472186287 Fax: 330478433383 Email: [email protected]
Ari Halvari Physicist Savonia University of Applied Sciences School of Engineering and Technology P.O. Box 6 Microkatu 1C Kuopio, 70201 Finland Phone: 00358447855579 Fax: Email: [email protected]
Ude Hangen Hysitron, Inc. Valley View Road Eden Prairie, MN 55344 USA Phone: 49-17-33-97-3781 Fax: Email: [email protected]
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Alexander Hartmaier Professor ICAMS, Ruhr University Bochum Stiepeler Strasse 129 Bochum, 44801 Germany Phone: 49-234-32-29314 Fax: 49-234-32-14984 Email: [email protected]
Kevin Hemker Department Chair Johns Hopkins University Department of Mechanical Engineering 223 Latrobe Hall, 3400 N. Charles Street Baltimore, MD 21218 USA Phone: 1-410-516-4489 Fax: 1-410-516-7254 Email: [email protected]
Jenna-Kathrin Heyer Ruhr-Universitat Bochum Institute for Materials Universitatsstrasse 150 Bochum, 44780 Germany Phone: 49-234-322-9159 Fax: 49-234-321-4235 Email: [email protected]
Barbara Hickernell Executive Director Engineering Conferences International 32 Broadway, Suite 314 New York, NY 10004 USA Phone: 1-212-514-6760 Fax: 1-212-514-6030 Email: [email protected]
Andrea Hodge Professor University of Southern California 3650 McClintock Ave, OHE 430 Los Angeles, CA 90089-1453 USA Phone: 1-213-740-4225 Fax: 1-213-740-8071 Email: [email protected]
Philip Howie University of Cambridge Pembroke Street Cambridge, CB2 3QZ United Kingdom Phone: 44-1223-33-4339 Fax: 44-1223-33-4567 Email: [email protected]
Shelby Hutchens California Institute of Technology 1200 East California Boulevard MC 309-81 Pasadena, CA 91125 USA Phone: 1-626-395-4416 Fax: 1-626-395-8868 Email: [email protected]
Jiseong Im POSTECH RIST 3-DONG 3123 San 31, Hyoja-Dong Nam-Gu Pohang, 790-784 Korea Phone: 82-54-279-5127 Fax: 82-54-279-5155 Email: [email protected]
Peter Imrich Austrian Academy of Sciences,Erich Schmid Institute of Materials Science Jahnstrasse 12 Leoben, 8700 Austria Phone: 43-38-4280-4313 Fax: 43-38-4280-4116 Email: [email protected]
Bongkyun Jang Korea Institute of Machinery and Materials 119 Building #13, 104 Sinseongno Yuseong-Gu Deageon, 305-343 South Korea Phone: 82-42-868-7850 Fax: 82-42-868-7884 Email: [email protected]
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Vincent Jardret Michalex 63, Rue La Bruyere Rueil Malmaison, 92500 France Phone: 33-66-04-79805 Fax: 33-1-64-46-1203 Email: [email protected]
Andrew Jennings California Institute of Technology 1200 East California Boulevard MC 300-81 Pasadena, CA 91125 USA Phone: 1-626-395-4416 Fax: 1-626-395-8868 Email: [email protected]
Dorte Jensen Heaf of Division Riso DTU Riso National Laboratory Materials Research Division Roskilde, 4000 Denmark Phone: 45-46-77-5701 Fax: 45-46-77-5758 Email: [email protected]
Antoaneta Kazandzieva Consultant 201 West 72nd Street PH 1-C New York, NY 10023 USA Phone: 1-212-874-6472 Fax: 1-212-874-6472 Email: [email protected]
Philippe Kempe Sales Manager CSM Instruments Rue De La Gare 4 Peseux, 2034 Switzerland Phone: 41325575621 Fax: 41325575610 Email: [email protected]
Nousha Kheradmand Saarland University Campus, Geb. D22 Institute for Methodic and Materials Sci Saarbrücken, 66123 Germany Phone: 49-681-302-5160 Fax: Email: [email protected]
Daniel Kiener Montanuniversitat Leoben Materials Physics Department Jahnstrasse 12 Leoben, 8700 Austria Phone: 43-3842-804-412 Fax: 43-3842-804-116 Email: [email protected]
Young-Cheon Kim Seoul National University 131dong-302ho Seoul National University Gwanak-ro 599, Gwanak-gu Seoul, 151-744 Korea Phone: 828848025 Fax: 828864847 Email: [email protected]
Christoph Kirchlechner University of Leoben Jahnstrasse 12 Leoben, 8700 Austria Phone: 38-42-804-301 Fax: 38-42-804-116 Email: [email protected]
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10/9/2011 through 10/14/2011
Stephan Kleindiek General Manager Kleindiek Nanotechnik GmbH Aspenhaustraße 25 Reutlingen, Baden-Württemberg 72770, Germany Phone: 49-71-21-345-3950 Fax: 49-71-21-345-395-55 Email: [email protected]
Thomas Kluensner Leoben Forschung GmbH Materials Center Roseggerstrasse 12 Leoben Styria, 8700 Austria Phone: 43-38-424-5922 Fax: 43-38-424-5922 Email: [email protected]
Sandra Korte University of Cambridge/University of Erlangen-Nurnberg Pembroke Street Cambridge, Cambridgeshire CB3 0AG, United Kingdom Phone: 44-12-2333-4339 Fax: 44-12-2333-4567 Email: [email protected]
Seok-Woo Lee Graduate Student Stanford University 79 Olmsted Rd. #103 Stanford, CA 94305 USA Phone: 1-650-799-1566 Fax: Email: [email protected]
Subin Lee POSTECH POSTECH RIST 3123 San 31, Hyoja-Dong Nam-Gu Pohang, 790-784 Korea Phone: 82-10-4876-9208 Fax: 82-54-279-5155 Email: [email protected]
Marc Legros Directeur De Recherches CEMES-CNRS 29 Rue Jeanne Marvig Toulouse, Midi Pyrénées 31055, 31055 France Phone: 33-562-257-842 Fax: 33-562-257-999 Email: [email protected]
Ruixing Li Professor School of Materials Science and Engineering, Beihang University 9-1501 XinKeXiangYuan, Zhongguancun HaiDianQv Beijing, 100190 China Phone: 86-10-8231-6500 Fax: 86-10-8231-6500 Email: [email protected]
Jochen Lohmiller Karlsruhe Institute of Technology Institute for Applied Materials Postbox 3640 Karlsruhe, 76021 Germany Phone: 49-721-608-2-5855 Fax: 49-721-608-2-2347 Email: [email protected]
Jean-Luc Loubet Director of Research LTDS/ECL/CNRS 36 Avenue Guy De Collongue Ecully Cedex 69134, France Phone: 33-4-7218-6281 Fax: 33-4-7843-3383 Email: [email protected]
Oleg Lysenko Institute for Superhard Materials 2, Avtozavodskaya Kiev, 04074 Ukraine Phone: 38-4-44-67-6615 Fax: 38-4-44-68-8632 Email: [email protected]
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Verena Maier University Erlangen-Nürnberg University Erlangen-Nürnberg General Materials Properties Martensstrasse 5 Erlangen, Bavaria, 91058 Germany Phone: 49-913-1852-7474 Fax: 49-913-1852-7504 Email: [email protected]
David Mercier PhD Student CEA-LETI Minatec 17 Rue Des Martyrs Grenoble, Isere, 38054 France Phone: 33-43-878-2340 Fax: 33-43-878-5140 Email: [email protected]
Benoit Merle University Erlangen-Nürnberg Department of Materials Science and Engineering, Institute I Martensstrasse 5 Erlangen, 91058 Germany Phone: 49-9131-8527485 Fax: 49-9131-8527504 Email: [email protected]
Johann Michler Director of Research EMPA Feuerwerkerstrasse 39 Thun, Bern CH-3602, Switzerland Phone: 41-58-765-6205 Fax: 41-33-228-4490 Email: [email protected]
Vladimir Milyavskiy Head of the Department Russian Academy of Sciences, Joint Institute for High Temperatures
Reiner Moenig Karlsruhe Institute of Technology Postfach 3640 Karlsruhe, 76021 Germany Phone: 49-721-608-22487 Fax: Email: [email protected]
Jon Molina-Aldareguia Researcher IMDEA-Materials IMDEA Materials Institute C/o Professor Aranguren S/n, Madrid 28040, Spain Phone: 34-91-549-3422 Fax: 34-91-550-3047 Email: [email protected]
Christian Motz Austrian Academy of Sciences Erich Schmid Institute Jahnstrasse 12 Leoben, A-8700 Austria Phone: 43-3842-804-101 Fax: 43-3842-804-116 Email: [email protected]
Jaya Nagamani Indian Institute of Science Ceramics Laboratory Materials Engineering Department IISc, Bangalore Karnataka, 560012 India Phone: 91-92-41-801-1604 Fax: 91-80-2360-0472 Email: [email protected]
Engineering Conferences International Participants List
Nanomechanical Testing in Materials Research and Development Lanzarote, Canary Islands, Spain
10/9/2011 through 10/14/2011
William Nix Professor Stanford University Department of Materials Science and Engineering 496 Lomita Mall, Durand Building Rm. 117 Stanford, CA 94305-4034 USA Phone: 1-650-725-2605 Fax: 1-650-725-4034 Email: [email protected]
Sang Ho Oh Pohang University of Science and Technology (POSTECH) Dept. Materials Science and Engineering San 31, Hyoja-dong, Nam-gu POSTECH Pohang, 790-784 Korea Phone: ++82 54 279 2144 Fax: ++82 54 279 2399 Email: [email protected]
Warren Oliver Nanomechanics, Inc. 105 Meco Lane, Suite 100 Suite 100 Oak Ridge, TN 37830 USA Phone: 1-865-978-6490 x250 Fax: 1-888-381-5798 Email: [email protected]
Oskar Paris Montanuniversitaet Leoben Institute of Physics Franz-Josef-Strasse 18 Leoben, 8700 Austria Phone: 43-3842-402-4600 Fax: 43-3842-402-4602 Email: [email protected]
Kermit Parks Nanomechanics Inc. 105 Meco Lane Oak Ridge, TN 37830 USA Phone: 1-865-978-6490 Fax: 1-865-481-8455 Email: [email protected]
Sophie Pavan Engineer LTDS / Ecole Centrale De Lyon / Centrale Innovation 36 Avenue Guy De Collongue Ecully Cedex 69134, France Phone: 33-4-7218-6596 Fax: 33-4-7843-3383 Email: [email protected]
Janine Pfetzing-Micklich Ruhr University Bochum Institute for Materials Universitätsstrasse 150 Bochum, 44801 Germany Phone: 49-234-32-25934 Fax: 49-234-32-14235 Email: [email protected]
George Pharr Professor University of Tennessee 434 Dougherty Engineering Building Department of Materials Science and Engineering Knoxville, TN 37996-2200 USA Phone: 1-865-974-8202 Fax: 1-865-974-4115 Email: [email protected]
Jacques Rabier Directeur De Recherche CNRS INSTITUT P' UPR 3346 CNRS SP2MI Futuroscope Chasseneuil, 86960 France Phone: 33-5-49-49-67-32 Fax: 33-5-49-49-66-92 Email: [email protected]
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10/9/2011 through 10/14/2011
Rejin Raghavan EMPA Materials Science and Technology Labortory for Mechanics of Materials and Nanostructures Feuerwerkerstrasse 39 Thun, 3602 Switzerland Phone: 41-33-22-83-703 Fax: 41-33-22-84-490 Email: [email protected]
Nicholas Randall Vice-President CSM Instruments 197 1st Ave, Suite 120 Needham, MA 02494 USA Phone: 1-781-444-2250 Fax: 1-781-444-2251 Email: [email protected]
Frank Richter Chemnitz University of Technology Institute of Physics Chemnitz, 09107 Germany Phone: 49-37-15-313-8046 Fax: 49-37-15-312-1719 Email: [email protected]
Gunther Richter Max Planck Institute for Intelligent Systems Heisenbergstrasse 3 Stuttgart, 70569 Germany Phone: +49-711-689-3587 Fax: +49-711-689-3412 Email: [email protected]
Peter Schaaf Ilmenau University of Technology Institute of Micro & Nanotechnology Gustav-Kirchhoff-Strasse 5, Ilmenau, 98693 Germany Phone: 49-3677-69-3611 Fax: 49-3677-69-3171 Email: [email protected]
Matthias Schamel ETH Zurich, Laboratory of Nanometallurgy ETH Zurich, Department of Materials, LNM Wolfgang-Pauli-Strasse 10 HCI G503 Zurich, 8093 Switzerland Phone: 41-44-633-4954 Fax: 41-33-22-84490 Email: [email protected]
Simone Schendel Karlsruhe Institute of Technology Institute for Applied Materials Hermann-von-Helmholtz-Platz 1 Eggenstein-Leopoldshafen, BW 76344 Germany Phone: 49-721-608-25858 Fax: 49-721-608-22347 Email: [email protected]
Yoon Shin Pohang University of Science and Technology (POSTECH) San 31, Hyoja-Dong, Nam-Gu Pohang Cyungbuk, 790-784 South Korea Phone: 82-10-4856-6024 Fax: 82-54-279-5155 Email: [email protected]
Jignasa Solanki S.V.National Institue of Technology Chemical Engineering Department Surat, Gujarat 395 007, 395007 India Phone: 91-26-1220-1642 Fax: 91-26-1222-7334 Email: [email protected]
Wolfgang Stein General Manager SURFACE Systems + Technology GmbH + Co. KG Rheinstrasse 7 Hueckelhoven D41836, Germany Phone: 49-2433-970-305 Fax: 49-2433-970-302 Email: [email protected]
Alisa Stratulat Oxford University The Queens College Oxford, OX1 4AW United Kingdom Phone: 44-7-909-414-272 Fax: Email: [email protected]
John Swindeman CEO Nanomechanics, Inc. 105 Meco Lane Oak Ridge, TN 37830 USA Phone: 1-865-978-6490 Fax: 1-888-381-5798 Email: [email protected]
Ludovic Thilly Prof. Dr. University of Poitiers Institut Pprime, SP2MI, Bd Curie Futuroscope Chasseneuil, 86962 France Phone: 33-5-49-49-6831 Fax: 33-5-49-49-6692 Email: [email protected]
Christophe Tromas Institut Pprime - Université De Poitiers Institut Pprime, Dept PMM SP2MI, Bd. Marie et Pierre Curie, BP 30179 Chasseneuil Futuroscope Cedex, 86962 France Phone: 33-5-49-49-67-24 Fax: 33-5-49-49-66-92 Email: [email protected]
Aleksandrs Urbahs Riga Technical University Ruses 3-44 Riga, LV1029 Latvia Phone: 371-67-089-948 Fax: 371-67-089-968 Email: [email protected]
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Nanomechanical Testing in Materials Research and Development Lanzarote, Canary Islands, Spain
10/9/2011 through 10/14/2011
Alex Useinov FSI TISNCM 7a, Centralnaya Street Troitsk, Moscow Reg, 142190 Russia Phone: 7-499-272-2314 Fax: 7-499-400-6260 Email: [email protected]
Joost Vlassak Dean Harvard University, School for Engineering and Applied Sciences Materials Science & Mechanical Eng. Pierce Hall 308 29 Oxford Street Cambridge, MA 02138 USA Phone: 1-617-496-0424 Fax: 1-617-496-0601 Email: [email protected]
Stefan Wurster Austrian Academy Of Sciences, ErichSchmid Institute of Materials Science Jahnstrasse 12 Leoben Styria, 8700 Austria Phone: 43-3842-804-325 Fax: 43-3842-804-116 Email: [email protected]
Kong Yeap Fraunhofer Institute for Nondestructive Testing Maria-Reiche-Strasse 2 Dresden, 01109 Germany Phone: 49-351-88815-569 Fax: 49-351-88815-509 Email: [email protected]
Igor Zlotnikov Max Planck Institute of Colloids and Interfaces Biomaterials Department Am Muhlenberg 1 OT Golm Potsdam, 14424 Germany Phone: 49-331-567-9453 Fax: 49-331-567-9402 Email: [email protected]
Engineering Conferences International Engineering Conferences International (ECI) is a not-for-profit global engineering conferences program that has served the engineering/scientific community since 1962 as successor program to Engineering Foundation Conferences. ECI has received recognition as a 501(c)3 organization by the U.S. Internal Revenue Service and is incorporated in the State of New York as a not-for-profit corporation. The program has been developed and is overseen by volunteers both on the international Board of Directors and international Conferences Committee. More than 1,400 conferences have taken place to date. The conferences program is administered by a professional staff and the conferences are designed to be self-supporting.
ECI Mission
To serve the engineering/scientific community with international, interdisciplinary, leading edge engineering research conferences
ECI Purposes The advancement of engineering arts and sciences by providing a forum for the discussion of advances in the field of science and engineering for the good of mankind by identification and administration of international interdisciplinary conferences To work with engineering, scientific and social science societies and the interested general public to jointly sponsor conferences and to take other actions that will foster complementary programming. To initiate conferences that will have a significant impact on engineering education, research practice and/or development.
ECI Encouragement of New Conference Topics
The ECI Conferences Committee invites you to suggest topics and leaders for additional conferences and encourages you to submit a proposal for an ECI conference. Ideally, proposals should be submitted from 18 to 24 months in advance of the conference although the staff can work on a shorter timeline. The traditional format for an ECI conference is registration Sunday afternoon with technical sessions held each morning and evening through Thursday or Friday noon. Afternoons are used for informal gatherings, poster sessions, field trips, subgroup meetings and relaxation. This format has served well to build important professional networks in many areas. ECI welcomes proposals for shorter conferences and for conferences which span weekends in order to reduce the number of working days participants are away from their offices.
ECI Works With You ECI works with conference chairs in two complementary ways. First, an experienced member of the Conferences Committee acts as your technical liaison from the proposal stage through the conference itself. He or she is always available to consult with you on any conference issue. Second, after your proposal has been approved by the Conferences Committee, the ECI staff will assume responsibility for the administration of the conference. Your primary responsibilities will be recruiting the organizing committee, developing the technical program and securing third-party funding necessary to support the travel of key speakers. The responsibilities of ECI's "full service" staff include -- but are not limited to -- the following:
• Recommend, negotiate, contract and make substantial deposits for housing, meals,
meeting space, A/V equipment and tours. • Maintain web sites for the conference and for submission of abstracts. • Publicize via electronic and print media. • Administer all finances including grants, contributions and purchase orders. (ECI makes
grant funds available as soon as a grant is approved.) There is no need for chairs to set up a conference bank account or file tax returns for their conference.
• Process all applications and registrations.
• Produce bound program/abstracts book. • Contract for the publication of print or electronic proceedings, if any.
• Provide on-site staff during the conference.
For more information, please contact the ECI Director at [email protected]
