Detailed Programme and Abstract Proceedings · Dr. Fauzan Adziman Prof. Jeffrey Cross Mrs. Karen...

Detailed Programme and Abstract Proceedings UK-Japan Symposium 2015 on Materials Under Extreme Conditions: Effects of Temperature, High Strain Rate and Irradiation

http://www.eng.ox.ac.uk/solidmech/ukjapan2015

20 – 23 September 2015, University of Oxford, United Kingdom

Organised by University of Oxford and Tokyo Institute of Technology under the auspices of the UK-Japan Engineering Education League

http://www.eng.ox.ac.uk/solidmech/ukjapan2015

UK-Japan Symposium on Materials Under Extreme Conditions: Effects of Temperature, High Strain Rate and Irradiation Oxford, United Kingdom, 20-23 September 2015

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Contents

Foreword ................................................................................................................................................. 2

Organising Committee and Editors ......................................................................................................... 2

Map of Pembroke College ...................................................................................................................... 4

Programme overview .............................................................................................................................. 5

Detailed programme ............................................................................................................................... 6

Topics for student groupwork presentation ........................................................................................... 9

Name list for the groupwork presentation ........................................................................................... 10

List of Abstracts and Abstracts .............................................................................................................. 11


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Foreword

In many industrial sectors – for instance those dealing with power generation,

transportation, infrastructure and defence – advanced alloys are being pushed to the

very limits of their capability. Examples include ever higher operating temperatures and

pressures, high strain rates and harsh environments involving corrosion and nuclear

irradiation. These are materials required to work under extreme conditions.

What impact do these hostile environments have on the material’s operating lifetimes?

How do engineers design with them to meet industry’s needs but also to ensure the

safety demanded by society? What is the underlying material science that allows for

effective use of these advanced materials at extreme conditions?

To address these pressing issues, a UK-Japan Symposium on Materials Under Extreme

Conditions will bring together leading experts from around the world. Emphasis will be

placed on cutting-edge science and research, with plenty of time for discussion and

interaction including a groupwork project for students. The symposium is being

organised jointly by the University of Oxford* and Tokyo Institute of Technology, under

the auspices of the UK-Japan Engineering League†.

Organising Committee and Editors

University of Oxford Tokyo Institute of Technology

Prof. Roger C. Reed Prof. Kikuo Kishimoto

Dr. Fauzan Adziman Prof. Jeffrey Cross

Mrs. Karen Bamford Prof. Masao Takeyama

* As the oldest university in the English-speaking world, University of Oxford is a unique and historic institution. Teaching existed at Oxford in some form in 1096 and developed rapidly from 1167. † The UK-Japan Engineering Education League was founded at Tokyo Tech in March 2014, where it held its first symposium. A second meeting took place at UCL in London in September 2014. The league consists of more than 20 Japanese and UK research universities which hold meetings to exchange information, to establish best practice in engineering education and to promote education through research.


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Keynote Lectures

Role of Metals in Society Prof. Roger C. Reed University of Oxford

Novel Concept of Alloy Design for Power Generation Prof. Masao Takeyama Tokyo Institute of Technology

Nickel Superalloys for Jet Engine Applications Prof. Cathie Rae University of Cambridge

High-temperature Oxidation of Metals Prof. Shigenari Hayashi Tokyo Institute of Technology

Effects of Nuclear Irradiation of Structural Alloys Prof. David Armstrong University of Oxford

Titanium Alloys at the Extreme Prof. David Dye Imperial College London

Technical Lectures

Thermal Barrier Coatings Dr. Rudder Wu NIMS, Japan

Dynamic Failure of Materials and Structures Prof. Kazuaki Inaba Tokyo Institute of Technology

Modelling Methods for Design of New Alloys Dr. Alessandro Mottura University of Birmingham

Thermal Mechanical Fatigue Prof. Johan Moverare Linköping University, Sweden

Spraying Technology for Coatings Dr. Atsushi Sato University of Oxford

Role of Physics-based Modelling Dr. Fauzan Adziman University of Oxford

Plasticity and Beyond in Nickel Superalloys Prof. Motoki Sakaguchi Tokyo Institute of Technology

Materials at High Strain Rates Dr. Antonio Pellegrino University of Oxford

Overview of 9Cr-1Mo Steel Oxidation Behaviour in Advanced Gas Cooled Reactors

Dr. Aya Shin EDF Energy, UK


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Map of Pembroke College


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Programme overview

With opening and introductory remarks by

Prof. Roger C. Reed University of Oxford

Prof. Kikuo Kishimoto Tokyo Institute of Technology

Prof. Roderick Smith Imperial College London

Minister (Economic) Hiroshi Matsuura

Embassy of Japan in the United Kingdom

Sunday, 20th September 2015

Monday, 21st September 2015

Tuesday, 22nd September 2015

Wednesday, 23rd September 2015

Breakfast* starts at 08.00 for lecture starts at 09.00

Refer to detailed programme below

Keynote lectures

(3 x 40 min)

Keynote lectures

(3 x 40 min)

Group presentations by

student (3 groups)

Coffee break Coffee break Coffee break

Student presentations (4 x 20 min)

Student presentations (4 x 20 min)

Group presentations by

student (3 groups)

Lunch in Hall Lunch in Hall Lunch in Hall

Groupwork project for students

Networking and discussion for

other delegates

Coffee during session

Technical lectures

(4 x 20 min)

Departures

Registration

Coffee break

Poster session Technical lectures

(4 x 20 min)

19.00 Welcome drinks reception & dinner Dinner Formal dinner

* Breakfast in Dining Hall is only for delegates who stay at Pembroke College Oxford.


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Detailed programme

Sunday 20 September 2015 13.30 Registration

Preparation: for students to attach posters before 15.30 hrs Harold Lee Room

16.00 Student poster session and competition* *Winners of the best 8 posters, which will be selected by all delegates including a panel of judges, are entitled to do oral presentation on 21st or 22nd September Chairs: Dr Fauzan Adziman, Prof. Roger Reed, Prof. Kikuo Kishimoto

19.00 Welcome drinks reception and dinner Introductory remarks by Prof. Roger Reed (Oxford University) and Prof. Masao Takeyama (Tokyo Institute of Technology)

Hall

Monday 21 September 2015 08.00 Breakfast* Hall

Keynote lectures and student presentations Chair: Prof. Roger Reed

09.00 Keynote: Role of Metals in Society Prof. Roger Reed University of Oxford, UK

Harold Lee Room

09.40 Keynote: Novel Concept of Alloy Design for Power Generation Prof. Masao Takeyama Tokyo Institute of Technology, Japan

10.20 Keynote: Titanium Alloys at the Extreme Prof. David Dye Imperial College London, UK

11.00 Coffee 11.30 Student presentation 1 Harold Lee Room 11.50 Student presentation 2 12.10 Student presentation 3 12.30 Student presentation 4 12.50 Lunch Hall

Groupwork projects for students



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Chair: Prof. Jeffrey Cross

14.00 Groupwork project for students Coffee will be served during session

Harold Lee Room

Networking and discussion for other delegates 14.00 Networking and discussion

Coffee will be served during session Senior Common Room Parlour

16.30 Walking tour of Oxford by a professional guide

Depart from Harold Lee Room

19.00 Dinner Hall Tuesday 22 September 2015 08.00 Breakfast* Dining Hall

Keynote lectures and student presentations Chair: Prof. Roger Reed 09.00 Keynote: Nickel Superalloys for Jet Engine Applications

Prof. Cathie Rae University of Cambridge, UK

Harold Lee Room

09.40 Keynote: High-Temperature Oxidation of Metals Prof. Shigenari Hayashi Tokyo Institute of Technology, Japan

10.20 Keynote: Effects of Nuclear Irradiation of Structural Alloys Prof. David Armstrong University of Oxford, UK

11.00 Coffee 11.30 Student presentation 5 Harold Lee Room 11.50 Student presentation 6 12.10 Student presentation 7 12.30 Student presentation 8 12.50 Lunch Dining Hall

Technical lectures Chair: Prof. Masao Takeyama 14.00 Technical Lecture: Thermal Mechanical Fatigue

Prof. Johan Moverare Linköping University, Sweden

Harold Lee Room

14.20 Technical Lecture: Dynamic Failure of Materials and Structures Prof. Kazuaki Inaba Tokyo Institute of Technology, Japan



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14.40 Technical Lecture: Materials at High Strain Rates Dr Antonio Pellegrino University of Oxford, UK

15.00 Technical Lecture: Role of Physics-based Modelling Dr Fauzan Adziman University of Oxford, UK

15.20 Coffee

Technical lectures Chair: Prof. Cathie Rae 15.50 Technical Lecture: Plasticity and Beyond in Nickel

Superalloys Prof. Motoki Sakaguchi Tokyo Institute of Technology, Japan

Harold Lee Room

16.10 Technical Lecture: Modelling Methods for Design of New Alloys Dr Alessandro Mottura University of Birmingham, UK

16.30 Technical Lecture: Thermal Barrier Coatings Dr Rudder Wu National Institute of Materials Science, Japan

16.50 Technical Lecture: Spraying Technology for Coatings Dr Atsushi Sato University of Oxford, UK

17.10 Technical Lecture: Overview of 9Cr-1Mo Steel Oxidation Behaviour in Advanced Gas Cooled Reactors Dr Aya Shin EDF Energy, UK

18.30 Drinks reception and group photo session Garden in front of Hall*

19.00 remarks at 19.20

Formal dinner Remarks by Prof Roderick Smith (Imperial College London), Prof Kikuo Kishimoto (Tokyo Institute of Technology), and Minister (Economic) Hiroshi Matsuura (Japan Embassy in the UK)

Hall

* Weather permitting, alternatively in Dining Hall.


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Wednesday 23 September 2015 08.00 Breakfast* Hall

Group presentation by students Chair: Prof. Jeffrey Cross 09.00 Group presentation by students – Group 1 Harold Lee Room 09.30 Group presentation by students – Group 2 10.00 Group presentation by students – Group 3 10.30 Coffee 11.00 Group presentation by students – Group 4 11.30 Group presentation by students – Group 5 12.00 Group presentation by students – Group 6 12.30 Wrap Up session and closing

Profs Kikuo Kishimoto, Masao Takeyama and Roger Reed 13.00 Lunch Hall 14.00 Departures

Addendum After the symposium we will host UK - Japan Engineering Education League meeting

Contact persons: Professors Jeffrey Cross and Kikuo Kishimoto (Tokyo Institute of Technology), Roderick Smith (Imperial College London), Roger Reed and Steve Sheard (University of Oxford). Time: Wednesday, 23 September 2015, 13.30 -15.00 Location: Senior Common Room (SCR) Parlour, Pembroke College Oxford.

Topics for student groupwork presentation 1. Ph.D. Program Training: Comparison and analysis between Japan and UK/Europe Universities 2. Energy Policy in UK/Europe and Japan: Similarities and Differences 3. Science or Engineering: What Contributes More to Society? 4. The Public Perception of Science and Engineering in UK/Europe and Japan: How Do They Differ? 5. Possibilities for Recycling of Metals: Japan and UK/Europe 6. New Propulsion Strategies for Cars, Trains and Airplanes



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Name list for the groupwork presentation*

No First Name Surname Name of Institution Group 1

1 Tomohisa Kojima Tokyo Institute of Technology, Japan 2 Akira Yamauchi Tokyo Institute of Technology, Japan 3 Viktor Norman Linköping University, Sweden 4 Paraskevas Kontis University of Oxford, UK 5 Ana Casanova University of Cambridge, UK

Group 2 6 Yuri Iguchi Tokyo Institute of Technology, Japan 7 Hiromu Hisazawa Tokyo Institute of Technology, Japan 8 Mattias Calmunger Linköping University, Sweden 9 Andre Nemeth University of Oxford, UK

10 Abigail Ackerman Imperial College London, UK Group 3 11 Yo Kan Tokyo Institute of Technology, Japan 12 Hidekazu Arai Tokyo Institute of Technology, Japan 13 Sohya Kudoh Tokyo Institute of Technology, Japan 14 Lluís Pérez Caro Luleå University of Technology, Sweden 15 Enrique Alabort University of Oxford, UK

Group 4 16 Inci Akcam Tokyo Institute of Technology, Japan 17 Yuji Takeda Kyushu University, Japan 18 Samuel Hammarberg Luleå University of Technology, Sweden 19 Angelos Evangelou University of Southampton, UK 20 Sabin Muntean University of Oxford, UK

Group 5 21 Mari Yoshihara Tokyo Institute of Technology, Japan 22 Shuntaro Ida Tokyo Institute of Technology, Japan 23 Kamal Goswami Birmingham University, UK 24 Yilun Gong University of Oxford, UK 25 Paul Mulvey Imperial College London, UK

Group 6 26 Daniel Barba University of Oxford, UK 27 Tomomi Sugiyama Tokyo Institute of Technology, Japan 28 Shunichi Nakayama Tohoku University, Japan 29 Bentang Arief Budiman Tokyo Institute of Technology, Japan 30 Ted Sjöberg Luleå University of Technology, Sweden 31 Regina Schlutter University of Cambridge, UK

Chair: Professor Jeffrey Cross (Tokyo Institute of Technology) Tutors: Dr Atsushi Sato (University of Oxford), Dr David Crudden (University of Oxford), Dr Aya Shin (EDF Energy, UK – PhD from University of Cambridge), Dr Rudder Wu (NIMS – PhD from Imperial College London), Dr Kosuke Takahashi (Tokyo Institute of Technology), Dr Fauzan Adziman (University of Oxford)

* All 31 students are post-graduate students


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List of Abstracts and Abstracts


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List of Abstracts (Following alphabetical order of first author’s surname)

Keynote Lectures

Effects of Irradiation on Structural Nuclear Alloys ................................................................................................... 15 David E.J Armstrong ............................................................................................................................................. 15

High-Temperature Oxidation of Metals ................................................................................................................... 16 Shigenari Hayashi ................................................................................................................................................. 16

Yield and Creep Mechanisms in Superalloys ............................................................................................................ 17 C.M.F Rae, O.M.M.D. Mésse, N. Tabrizi and Y. Wang-Koh .................................................................................. 17

Technical Lectures

Role of Physics-based Constitutive Modelling of Metals ......................................................................................... 18 Fauzan Adziman*, Nik Petrinic, Roger Reed ......................................................................................................... 18

Dynamic Failure of Materials and Structures ........................................................................................................... 19 Kazuaki Inaba*, Kosuke Takahashi, Kikuo Kishimoto ............................................................................................ 19

Modelling Methods for Design of New Alloys.......................................................................................................... 20 Alessandro Mottura ............................................................................................................................................. 20

Thermal Mechanical Fatigue .................................................................................................................................... 21 Johan Moverare ................................................................................................................................................... 21

Materials at High Strain Rate ................................................................................................................................... 22 Antonio Pellegrino*, Nik Petrinic ......................................................................................................................... 22

Effect of Plastic and Creep Strains on the Microstructural Changes in a Single Crystal Ni-base Superalloy ........... 23 Motoki Sakaguchi 1,*, Masakazu Okazaki 2 ........................................................................................................... 23

Manufacture of Ultra-low Segregation Billets to Enable Novel Ni Superalloy Compositions for Extreme Condition Applications.............................................................................................................................................................. 24

Atsushi Sato1, Masaki Taneike2, Ikuo Okada2, Patrick S. Grant1,* ......................................................................... 24 Overview of 9Cr-1Mo Steel Oxidation Behaviour in Advanced Gas Cooled Reactors ............................................. 25

Aya Shin *, Eleanor Laney, and Jonathan Pearson ............................................................................................... 25 On the Mechanisms and Mitigation of Volcanic Ash Attack on YSZ Thermal Barrier Coatings ............................... 26

Rudder Wu ........................................................................................................................................................... 26

Post-Graduate Student Posters and Presentations

The Effect of Thermal Processing on Secondary Alpha ............................................................................................ 27 Abigail K Ackerman*, David Dye ........................................................................................................................... 27


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A Study of Superplasticity in Ti-6Al-4V ..................................................................................................................... 28 Enrique Alabort, Roger C. Reed ............................................................................................................................ 28

Degradation of Fibre/Matrix Interfacial Properties due to Fatigue Loading ........................................................... 29 Hidekazu Arai*, Bentang Arief Budiman, Kosuke Takahashi, Kazuaki Inaba, Kikuo Kishimoto ............................ 29

Microtwinning in Nickel-Based Superalloys ............................................................................................................. 30 Daniel Barba1, Enrique Alabort 1, Paraskevas Kontis 2, Antoine Jérusalem 1, Roger C. Reed 1 ............................. 30

An Efficient Interphase Strength Evaluation of Fibre/Matrix Composite by Using Characteristic Length ............... 31 Bentang A. Budiman*, Kosuke Takahashi, Kazuaki Inaba, Kikuo Kishimoto ......................................................... 31

Surface Phase Transformation in Austenitic Stainless Steel Induced by Cyclic Oxidation in Humidified Air ........... 32 Mattias Calmunger 1,*,Robert Eriksson 2, Guocai Chai 1,3, Sten Johansson 1, Johan J. Moverare 1 ....................... 32

Oxidation Behavior of a Single Crystal Ni-based Superalloy at Low Service Temperatures .................................... 33 Angelos Evangelou 1,*, Philippa Reed 1, Scott Lockyer 2, Katherine Soady 2 ......................................................... 33

Oxidation of Nickel-based Superalloys: Modelling & Validation ............................................................................. 34 Yilun Gong 1,*, Henrik Larsson 2, Roger Reed 1, 3 ................................................................................................... 34

Ab Initio Study of the Effect of Solute Atoms on The Vacancy Diffusion in Ni-based Superalloys .......................... 35 Kamal Nayan Goswami*, Alessandro Mottura ..................................................................................................... 35

Modelling and Analysis of Porous Core Material for Steel Laminates ..................................................................... 36 Samuel Hammarberg ........................................................................................................................................... 36

Effects of Ti/Nb Ratio on Nanoindentation Hardness in High Strength Ni-based Superalloys ............................... 37 Hiromu Hisazawa 1,*, Fauzan Adziman 2, David J Crudden2, David E.J. Armstrong3, Roger C Reed2 .................... 37

Precipitation of GCP and TCP Phases at Grain Boundaries in Wrought Ni- base Alloys .......................................... 38 Shuntaro Ida *, Satoru Kobayashi, Masao Takeyama ........................................................................................... 38

Regeneration of Chitin using Conventional Organic Solvents and its Functional Gel Membrane ........................... 39 Yuri Iguchi 1,*, Tomokazu Iyoda 1,2, Keiji Nagai 1,2 ................................................................................................. 39

Growth and Collapse of a Single Bubble near a Plate by Spark Discharge in Water ................................................ 40 Akcam Inci*, Inaba Kazuaki, Takahashi Kosuke, Kishimoto Kikuo ........................................................................ 40

The Improving Graphene Transfer by Changing Transfer Variables ........................................................................ 41 Yo Kan 1,2,*, Ella Carlsen-O'Conor 1, Adrian Murdock 1, Christian van Engers 3, Nicole Grobert 1......................... 41

Wave Propagation across Solid-Fluid Interface with Fluid-Structure Interaction .................................................... 42 Tomohisa Kojima*, Kazuaki Inaba, Kosuke Takahashi, Kikuo Kishimoto .............................................................. 42

The Effect of Boron on Grain Boundary Character in a New Polycrystalline Superalloy ......................................... 43 Paraskevas Kontis 1,*, Hanis A. Mohd Yusof 1, Stella Pedrazzini 1, Katie L. Moore 2, Paul A.J. Bagot 1, Michael P. Moody 1, Chris R.M. Grovenor 1, Roger C. Reed 1 ................................................................................................ 43

A Study on Si Surface Flattening Process and its Effect on Device Characteristics .................................................. 44 Sohya Kudoh*, Shun-ichiro Ohmi** ....................................................................................................................... 44

The Development of New Co-Ni Superalloys ........................................................................................................... 45 Paul Mulvey 1,*, Mark Hardy 2, David Dye 1 .......................................................................................................... 45

Microstructures and Mechanical Properties of ZrC-added Mo-Si-B alloys .............................................................. 46 Shunichi Nakayama*, Kyosuke Yoshimi ................................................................................................................ 46


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Intergranular Fracture at 800 deg C in Advanced Nickel-based Superalloys ........................................................... 47 Andre A.N. Nemeth*, David J. Crudden, David E.J. Armstrong, Roger C. Reed ................................................... 47

Lifetime Estimation of Heavy-Vehicle Engine Materials .......................................................................................... 48 Viktor Norman 1,*, Peter Skoglund 1,2, Johan Moverare 1 and Daniel Leidermark 3 ............................................. 48

Thermo-mechanical Characterization of a Nickel-based Superalloy ....................................................................... 49 Lluís Pérez Caro 1,2,*, Eva-Lis Odenberger 1,2,**, Per Thilderkvist 1,***, Mats Oldenburg 2,**** ................................ 49

Material Characterisation for Containment Dimensioning ...................................................................................... 50 Ted Sjöberg 1,*, Jörgen Kajberg 1, Mats Oldenburg 1 ............................................................................................ 50

Fabrication of Al-Cu/pure Al Clad Strips by Vertical-type Tandem Twin-roll Casting .............................................. 51 Tomomi Sugiyama 1,*, Yusuke Takayama 1, Yohei Harada 1, Shinji Kumai 1 ......................................................... 51

Effect of Strain Rate and Grain Diameter on Local Deformation Energy of Industrial Pure Iron ............................. 52 Yuji Takeda 1,*, Masatoshi Aramaki 2, Osamu Furukimi 2, Rintaro Ueji 3, Takashi Muzuguchi 4 ........................... 52

Synthesis of Well-defined Functional Polymer Particles by Living Dispersion Coordination Polymerization of Allene Derivatives .................................................................................................................................................... 53

Akira Yamauchi 1,*, Takayuki Omura 2, Yoshiyuki Oguchi 2, Hiroshi Yamauchi 2, Hiroki Nishiyama 1, Shinsuke Inagi 1, and Ikuyoshi Tomita 1 ............................................................................................................................... 53

In-situ Tensile Deformation Behaviour near Grain Boundary with and without Laves Phase in Novel Fe-Cr-Ni-Nb Steels at 1073 K ........................................................................................................................................................ 54

Mari Yoshihara*, Masao Takeyama ...................................................................................................................... 54


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Effects of Irradiation on Structural Nuclear Alloys

David E.J Armstrong Department of Materials, University of Oxford, Parks Road, Oxford, UK [email protected]

Abstract: The effect of irradiation damage on the mechanical properties of structural nuclear materials is of key concern in both future fission and fusion nuclear reactors. In these the temperatures and levels of irradiation seen will be considerably high than those in current fission reactors and as such the effect of radiation damage much be quantified. Due to the difficulties in working with neutron irradiated samples ion irradiations are a powerful tool for simulating this damage without the added expense of working with active materials. However how successfully they perform this task is unclear.

In this talk I will summarise our key findings on relating the effects of radiation damage on new materials for nuclear reactors, in particular focusing on tungsten alloys for use in fusion reactors. Tungsten is the key material for plasma facing components, but there is a lack of fundamental data regarding its behaviour under neutron irradiation. This work will start out with an overview of tungsten in fusion and move on to discuss ion irradiated samples of tungsten and tungsten-rhenium-osmium alloys studied using combinations of high temperature micro-mechanical testing, atom probe tomography and transmission electron microscopy. Finally initial work on neutron irradiated tungsten will be shown and compared with ion irradiated samples. The advantages and disadvantages of ion irradiation will be discussed and future research directions for tungsten alloys indicated.


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High-Temperature Oxidation of Metals

Shigenari Hayashi Department of Metallurgy and Ceramics Science, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1-S8-3, Ookayama, Meguro-ku, Tokyo, 152-8552, Japan [email protected]

Abstract: High-temperature oxidation (and/or corrosion) of metals is the phenomenon that metallic materials degrades at higher temperatures by reaction with mostly gas species, such as O2, S2, H2O, SO2, C, and N2, so on. Fast reaction of materials with those gas species causes rapid consumption of the metallic substrate, change in the substrate composition and microstructure, which decreases mechanical properties of alloys. Moreover, formation of thick reaction products may also be detrimental for heat-exchanging systems, such as boiler tubes. Therefor metallic substrate must be protected from high temperature environments. Preventing high-temperature oxidation is not possible since metals are thermodynamically much unstable than oxides and sulphides. Therefore protective oxide scale is usually used to reduce the “oxidation rate” and increase the lifetime of metallic materials at higher temperatures. As shown in Fig. 1, SiO2, Cr2O3 or Al2O3 scale can be a protective oxide scale to protect heat-resistant alloys and coatings, since those oxide scales are very stable and slow growing at higher temperatures. The protective oxide scale must be a homogeneous layer and formed by selective oxidation of alloying elements, therefore sufficient amount of Si, Cr and/or Al must be contained in the alloy. However, higher addition of those elements is usually detrimental for mechanical properties of alloys, and development of a protective oxide scale with lower addition of those elements is strongly required. In this presentation, fundamental of high-temperature oxidation will be explained initially and alloy design from high-temperature oxidation perspective will be discussed.

Keywords: protective oxide scale, oxidation and corrosion, heat resistant alloy.

Figure Protective oxide scales and their temperature capability.


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Yield and Creep Mechanisms in Superalloys

C.M.F Rae, O.M.M.D. Mésse, N. Tabrizi and Y. Wang-Koh Materials Science and Metallurgy, Cambridge University, 27 Charles Babbage Road, CB3 0FS, UK

Abstract: The study of superalloys has traditionally focussed on creep in single crystals and yield in polycrystals, as these properties are most critical for each application. However it is clear that as the volume fraction of the Jc of these alloys is increased to improve strength at increasingly high temperatures, the same mechanisms are seen in both. The strength of superalloys is associated with coherent ordered precipitates of Jc: in polycrystalline alloys the emphasis is on the role of the anti-phase boundaries through weak and strongly coupled dislocations but in single crystal alloys Kear Wilsdorf locking is quoted as the source of the increasing strength. Although not often a limiting factor in single crystal alloy design, yield is nevertheless important and is particularly so where stress concentrations result in low cycle fatigue challenges.

We present observations on yield in a range of commercial single crystal superalloys: CMSX-4�*, TMS138A, CMSX-10*, and also polycrystalline disc alloys, showing a range of dislocation mechanisms depending on the stress and the temperature. Some common features are seen, but also some important differences. Closely paired dislocations forming dipoles in tests interrupted shortly after the yield point and discus the role these play in determining the strength of the alloy. At higher temperature we also see creep-like mechanisms involving stacking faults at around the yield point. These will be compared with observations from high stress creep and micro-structures seen in samples fatigued around the yield point.

* CMSX-4 and CMSX-10 are registered trademarks of Cannon Muskegon Corporation

Acknowledgement: This work was supported by Rolls-Royce plc and the EPSRC under Grant Numbers EP/H022309/1 and EP/H500375/1.


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Role of Physics-based Constitutive Modelling of Metals for Simulation of Transformative Manufacturing Processes

Fauzan Adziman*, Nik Petrinic, Roger Reed Solid Mechanics and Materials Engineering Group, Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, UK *[email protected]

Abstract: Constitutive modelling at two different length scales is introduced to accommodate underlying physical mechanisms of high grade alloy systems subjected to large deformations, high strain-rates and high temperatures – extreme conditions inherited by transformative manufacturing processes of gas turbines such as solid-to-solid joining processes and high-speed machining. The principles of thermodynamics are used as point of departure to formulate the constitutive models, leading to thermodynamically-consistent model and physically motivated evolution equations of internal state variables. Key aspects of solid mechanics to stress and strain formulations are explained; this includes the use of hypo- and hyperelastic formulations, and incorporation of plastic anisotropy. Numerical integrations of both explicit and implicit schemes are discussed, along with a multi-scale framework of computational homogenisation linking micro- to macroscale. Results show integrated physics-based constitutive models with experiments hold vital roles for effective development of advanced metals by the bottom up approach – from designing the alloys up to manufacturing, testing and commissioning.

Keywords: physics-based constitutive modelling, manufacturing process, advanced metals.

Acknowledgement: Funding from the Engineering and Physical Sciences Research Council (EPSRC) UK through grant EP/K028316/1, for the MAST project, is gratefully acknowledged.

Figure. An integrated approach in physics-based constitutive modelling – from mathematical and materials modelling, to simulation of manufacturing processes and applications.


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Dynamic Failure of Materials and Structures

Kazuaki Inaba*, Kosuke Takahashi, Kikuo Kishimoto Department of Mechanical Sciences & Engineering, Tokyo Institute of Technology, 1-3-1 Ookayama, Meguro-ku, 152-8550, Tokyo Japan *[email protected]

Abstract: Our study focuses on the response of a fluid-filled tubes under axial impact loading experimentally, numerically, and theoretically. The goal of our research is to clarify the interaction mechanism of flexural waves in tube wall and pressure waves in fluid. We used steel, aluminum, polycarbonate, and composites as specimen tubes and water, slurry, and water with air bubbles as fluid. The impact of a free-fall piston initiated pressure waves in the fluid and stress waves in the tube, which is consider to be similar phenomena as water hammer or explosion in a piping system. The waves are traveling through the fluid-filled tubes and hoop strains increased when waves arrived at gage locations. From strain signals, we can measure wave speeds, known as the Korteweg-Joukowsky speeds, from the arrival times. In the classical theory, the speed depends on the Young’s modulus of tube, bulk modulus of fluid, diameter of tube, and thickness of tube wall. We confirmed that wave speeds with various specimen tubes and fluids could be estimated by the classical theory even with composite tubes by some extensions of the classical theory. The wave speed is important because pressure surge can be estimated by the Joukowsky pressure calculated by products of the wave speed, density of fluid, and boundary speed. When the pressure increases, the tube will get damage. With aluminum tubes and composite tubes, we observed tube damages and raptures. With steel tubes, large plastic deformations were observed as well as elastic tube deformations by traveling waves.

Keywords: water hammer, fluid-structure interaction, impact response.

Figure. Damaged and raptured tubes (a) CFRP, (b) GFRP, (c) mild steel.

(a) (b)

(c)


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Modelling Methods for Design of New Alloys

Alessandro Mottura School of Metallurgy and Materials, University of Birmingham [email protected]

Abstract: Creep deformation mechanisms markedly change with chemistry in the superalloys. The planar faults observed after creep in Co-based superalloys are dramatically different to the planar faults observed after creep in Ni-based superalloys. This happens, in part, due to the effect of chemistry on planar fault energies. In this work, using a variety of modeling methods, the variation of planar fault energies across wide compositional ranges in multi-component Co-based alloys is investigated. Results are discussed in light of high-resolution energy dispersive spectroscopy and high-resolution scanning transmission electron microscopy results showing segregation of elements such as Ta and W to the superlattice intrinsic stacking faults. Although Ta additions may produce an increase in stacking fault energies, the presence of other solute elements can lead to synergetic effects, which instead minimize the value of stacking fault energies. This has ramifications on currently ongoing alloy-design efforts.

Keywords: alloy design, planar fault energies

Figure. A) Superlattice instrisic stacking fault energy calculations in the Co3Al-Co3W-Co3Ta pseudo-ternary and b) how the superlattice intrinsic stacking fault energy may vary

with composition. A contour line at 0 mJ/m2 is drawn for clarity. Negative superlattice intrinsic stacking fault energies correspond to a stabilization of the D019 phase.


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Thermal Mechanical Fatigue

Johan Moverare Division of Engineering Materials, Department of Management and Engineering, Linköping University, SE-581 83 Linköping, Sweden [email protected]

Abstract: Nickel-based superalloys are designed to withstand extreme conditions of temperature and loading during operation. Their performance in critical hot gas path components such as blades and vanes largely limits the durability of modern gas turbines. Typically, components experience complicated and inter-related thermal and mechanical loading, especially during engine start-up and shut down. The thermal gradients in conjunction with mechanical constraints and the time variation of both the temperature and the stresses may eventually lead to thermal mechanical fatigue (TMF) damage. TMF is also growing in importance due to the efficiency of modern cooling systems, and the manner in which turbines and associated turbomachinery are now being operated. Unfortunately, at the present time, relatively little research has been carried out particularly on TMF of single crystal (SX) superalloys. In the present work, emphasis will be placed upon describing: (i) the nature of the testing method, the challenges involved in ensuring that an given testing methodology is representative of engine conditions (ii) the behaviour of a typical Re-containing second generation alloy such as CMSX-4, and its differing performance in out-of-phase/in-phase loading and crystallographic orientation and (iii) the differences in behaviour displayed by the Re-containing alloys and new Re-free variants such as STAL-15. It is demonstrated that single crystal superalloys are prone to different degradation mechanisms involving for example microtwinning, TCP precipitation and recrystallisation.

Keywords: Fatigue, TMF, Nickel-based superalloys, Twinning, recrystalization.

Figure. Microstructure for a single crystal superalloy subjected to OP TMF-loading in the 100-

750qC temperature range showing twinning, TCP-formation and recrystallization


22

Materials at High Strain Rate

Antonio Pellegrino*, Nik Petrinic Department of Engineering Science, University of Oxford, Oxford OX1 3PJ, United Kingdom *[email protected] Abstract: The understanding of the physical phenomena governing the response of materials and structures subjected to extreme thermo-mechanical loading is of paramount importance in many sectors, particularly in transportation and in defence. The consequences of impact loading due to collision or explosion are regularly severe, often threatening the lives of people involved. Hence the desire to conceive new engineering materials and to design optimal architectures of engineering systems and structures. This process relies on accurate and reliable experimental methods for the determination of the material response to dynamic loading and on the integration of experimental and numerical approaches in order to provide better understanding of the physical phenomena excited by such extreme loading conditions. The methodology for the determination of rate dependent behaviour of advanced engineering materials as well as behaviour of specific naturally occurring materials is herein presented. Emphasis is given to procedures relevant to the characterization of materials presenting dissimilar responses and occasionally opposite challenges related to the experimental determination of their properties. Specific attention is given to the characterisation of ductile metallic alloys. These are subjected, during high rate tensile testing, to severe strain localization and adiabatic heating, leading to multi-axiality of the stress state and affecting substantially the effective strain rate. Peculiar experimental techniques relevant to soft, brittle and granular materials are also assessed. Moreover the application of full field digital image correlation techniques on ultra-high speed cameras footage and the optimization of specimen geometries are discussed. Keywords: Hopkinson Bar, necking, true strain rate

Figure. Strain localization during high strain rate characterisation of ductile metallic alloys


23

Effect of Plastic and Creep Strains on the Microstructural Changes in a Single Crystal Ni-base Superalloy

Motoki Sakaguchi 1,*, Masakazu Okazaki 2 1. Department of Mechanical Control Engineering, Tokyo Institute of Technology, Japan 2. Department of Mechanical Engineering, Nagaoka University of Technology, Japan *[email protected]

Abstract: Single crystal Ni-base superalloys have regularly arrayed composite microstructure consisting of cuboidal gamma prime precipitates surrounded by narrow channels of gamma matrix. It has been well known that the microstructure changes accompanying with directional coarsening, so-called rafting, due to the creep stress. Nowadays, several investigations have indicated that the directional coarsening could occur by a simple plastic pre-strain and a subsequent thermal aging. In this study, effects of plastic and creep strains on microstructural changes in a Ni-base single crystal superalloy, CMSX-4, were experimentally and numerically investigated. Solid cylindrical specimens were subjected to many types combinations of uni-axial plastic strains and creep strains. A series of experiments revealed that the effect of the plastic and creep strains on the morphological changes were quantitatively different. In order to rationalize these experimental results, elastic-plastic and creep analysis using FEM were carried out, taking account of various microstructural factors such as temperature dependence of the lattice misfit as well as the difference in the inelastic deformation behaviors between gamma matrix and gamma prime precipitates. The analytical results showed that the morphological changes were promoted depending on the inelastic strain gap between the matrix and the precipitates, which was quantitatively different between under the elastic-plastic and the creep conditions.

Keywords: Ni-base superalloy, single crystal, plastic strain, creep strain, microstructural changes, rafting, lattice misfit.


24

Manufacture of Ultra-low Segregation Billets to Enable Novel Ni Superalloy Compositions for Extreme Condition Applications

Atsushi Sato1, Masaki Taneike2, Ikuo Okada2, Patrick S. Grant1,* 1. Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK 2. Takasago R&D Centre, Mitsubishi Heavy Industries, 1-1 Shinhama 2-chome, Arai-cho, Takasago,

Hyogo 676-8686, Japan *[email protected]

Abstract: An arc spray forming process for the manufacture of billets of advanced metallurgical alloys has been developed that combines continuous atomisation of two consumable large diameter wires with billet spray forming technology. The new process has been explored for the manufacture of complex composition polycrystalline nickel-based superalloy billets for high temperature applications, exploiting the inherent refined and low-segregation nature of the as-sprayed microstructure. Critically, the possibility of using the spray formed billets without any additional downstream consolidation processing, as is typically required, has been studied. Through a series of process innovations and process parameter optimisation, as-sprayed billets with low and high temperature mechanical properties better than cast-wrought equivalents have been produced. Key features of the process are: (i) relatively high metal flow rate of ~0.6 kg/min and current of 500 A to ensure elimination of layering in the microstructure; (ii) careful on-line control of the deposition chamber atmosphere to control any oxygen and nitrogen pick-up; (iii) the introduction of an additional secondary atomiser to control deposition dynamics and to decrease the gas to metal flow rate to ~2.0; and (iv) the development bespoke post-deposition heat treatments.

Keywords: nickel superalloys, spray forming, manufacture.


25

Overview of 9Cr-1Mo Steel Oxidation Behaviour in Advanced Gas Cooled Reactors

Aya Shin *, Eleanor Laney, and Jonathan Pearson Chemistry and CO2 Oxidation Group, Nuclear Generation, EDF Energy, Barnwood, GL4 3RS, UK *[email protected]

Abstract: EDF Energy operates seven Advanced Gas Cooled Reactors (AGRs) in the UK to produce electricity. CO2 is used as the coolant gas in the AGRs, and 9Cr-1Mo ferritic steels (9Cr steels) are extensively used in the tubing for the evaporator and primary superheater sections. These steels are susceptible to both oxidation and carburisation in CO2 dominated coolant fluids under the gas pressure of 450-600 psi at 300°C to 540°C. The oxidation process of 9Cr steels has two stages: a protective regime in which a duplex protective oxide forms and the oxidation rate reduces with time, and a breakaway oxidation regime, which is characterised by fast, linear kinetics. The anticipated oxidation behaviour in the AGR operating environment was protective; however long term accelerated testing suggests that, under plant conditions, there is a low but finite probability of breakaway oxidation occurring. This can threaten the operational life of the AGRs, yet while modelled empirically the mechanism of breakaway oxidation is not fully understood.

The 9Cr-1Mo Steel Carburisation/Oxidation R&D programme (Phase 3) has been ongoing since 2014. In Phase 3, the primary focus has been on understanding the mechanism of breakaway oxidation and developing realistic models, which can ultimately improve the current boiler tube assessment methodology. Currently six UK universities and three industrial partners are involved in the programme. An overview of the Phase 3 programme will be presented during the talk.

Keywords: 9Cr-1Mo Steels, Oxidation in CO2, Advanced Gas Cooled Reactor, Nuclear.


26

On the Mechanisms and Mitigation of Volcanic Ash Attack on YSZ Thermal Barrier Coatings

Rudder Wu National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan

Abstract: Yttria stabilized zirconia (YSZ) made thermal barrier coatings (TBCs) have been widely utilized in commercial aero engines for decades. Unlike the injection of airborne particles forming calcium-magnesium-alumino-silicate (CMAS) on TBCs, which has been widely investigated, the implications of volcanic ash deposition on TBCs are not well understood. Previously, it has been demonstrated that volcanic ash readily reacts with alumina around 1310°C, forming anorthite (CaAl2Si2O8), magnetite (Fe3O4), and spinel (Al1.75Mg0.889Mn0.351O4) as reactive products, having melting temperatures above that of the volcanic ash.

The present study continues to explore the possibility of using aluminum based oxides and alumina doped YSZ in the reaction with volcanic ash to form compounds with melting temperatures higher than the typical service temperatures of TBCs. I call this the ‘melting-temperature engineering’ approach to mitigate melting induced penetration of volcanic ash in TBCs.

Keywords: thermal barrier coatings (TBCs), volcanic ash, CMAS.

Figure. DTA results showing that volcanic ash reacts with alumina to form compounds with higher melting temperatures


27

The Effect of Thermal Processing on Secondary Alpha

Abigail K Ackerman*, David Dye Department of Materials, Imperial College, London, *[email protected]

Abstract: Ti-6Al-2Sn-4Zr-6Mo-0.1Si (Ti6246) is widely used in high temperature applications, such as high pressure compressor discs in gas turbine engines, due to its high specific strength, good corrosion resistance and low density. Its complex Witmanstätten microstructure is thought to be key in the resulting properties of the alloy. Secondary alpha growing within the surrounding beta matrix is of particular interest, as it is thought that the presence of this particular phase gives Ti6246 its high strength and good fatigue properties. The growth of secondary alpha is predominantly controlled by stages of thermomechanical processing. A cooling rate of 10°min-1 was applied from above the beta transus, with microstructures being fixed at a variety of temperatures via water quench. The resulting microstructures were then investigated using optical microscopy, scanning electron microscopy and electron backscattered diffraction, with a range of volume fractions of primary and secondary alpha being presented. Samples quenched at higher temperatures showed predominantly grain boundary alpha with little to no secondary alpha growth. Samples quenched at lower temperatures presented the final Widmansätten microstructure. It is thought that this is due to the amount of supersaturation that occurs during the processing, as presented by Semiatin et al. [1]. References [1] S.L. Semiatin, S.L. Knisley, P.N. Fagin, D.R. Barker, F.Zhang. Microstructure Evolution during Alpha-beta Heat Treatment of Ti-6Al-4V Metall and Mat Trans A Metallurgical and Materials Transactions A, 34.10 (2003): 2377-386.


28

A Study of Superplasticity in Ti-6Al-4V

Enrique Alabort, Roger C. Reed Department of Engineering Science, University of Oxford, Parks Road, Oxford, UK

Abstract: Superplasticity is vital in many industrial fields — medical, defense, aerospace, transport and sports among others — for the fabrication of metallic components of complex geometry. The inherent peculiarity of the effect has kept theorists fascinated for many years. But significant controversy exists concerning the deformation mechanisms which are operative. In particular, unequivocal evidence that supports precise details of the accommodation process — whether it is diffusion, dislocation accommodated, a combination of both or some sort of cooperative grain boundary — is unavailable. Traditionally, surface studies have been used to characterise superplasticity. These studies have relied in post-mortem observations. However, novel in-situ testing techniques are potentially significantly more powerful for the study of high-temperature deformation mechanisms. In this paper, the mechanisms of superplasticity in Ti-6Al-4V are discussed. In addition, superplasticity is studied under constant strain-rate conditions; this has allowed the regime of superplasticity to be pinpointed. For design purposes, this understanding is translated into validated material laws which are accurate and which capture the relevant phenomena. Microstructurally explicit material laws are proposed based upon the micromechanical modes of deformation which are shown to be operating. Validated material laws are then embedded into a numerical model and are used to simulate an industrially-relevant manufacturing process which is important for the construction of hollow, lightweight structures which are of significant practical importance for the aerospace sector.

Keywords: superplasticity, Ti-6Al-4V.


29

Degradation of Fibre/Matrix Interfacial Properties due to Fatigue Loading

Hidekazu Arai*, Bentang Arief Budiman, Kosuke Takahashi, Kazuaki Inaba, Kikuo Kishimoto

Department of Mechanical Sciences and Engineering, Tokyo Institute of Technology, Tokyo, 152-0033, Japan *[email protected]

Abstract: Interface of fibre/matrix composite has important role for overall composite performance as load bearing structures. Evaluation of interfacial properties and influence of fatigue on interface must be investigated for long–term safety of structures. Unlike matrix and fibre, fatigue behaviour of fibre/matrix interface is not clear, which leads to complex failure of composite under fatigue loading. Our group introduced a new method of evaluating interfacial strength using characteristic length on a stress contour of composite based on continuum damage mechanics. Capturing of stress contours is conducted by photo elasticity technique. Degradation of interfacial strength due to fatigue can be obtained by using single fibre fragmentation test, cyclic loading test and photo elasticity technique. In this study, a carbon fibre is replaced by a lead pencil because it is easy to obtain stress contours clearly. First, stress contours are observed when a lead pencil is broken during single fibre fragmentation test. Next, cyclic loading test is conducted and interrupted before a specimen is broken. Finally, the stress contours near the same crack are observed again. Characteristic lengths indicating the interfacial strength are measured from the images of photo elasticity technique before and after cyclic loading test. Interfacial strength decreased by 68%, from 4.19 MPa to 1.34 MPa due to fatigue loading.

Keywords: Fatigue, fibre/matrix composite, interfacial properties degradation, single fibre fragmentation.

(a) Before cyclic loading test (b) After cyclic loading test

Figure. Captured colour near a lead pencil crack


30

Microtwinning in Nickel-Based Superalloys

Daniel Barba1, Enrique Alabort 1, Paraskevas Kontis 2, Antoine Jérusalem 1, Roger C. Reed 1

1. Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX13PH, UK

2. Department of Materials, University of Oxford, Parks Road, Oxford, OX13PJ, UK

Abstract: The role of creep deformation in the range 700 to 850 °C is assuming greater importance for nickel-based superalloys. Why? The temperature of the rim of turbine discs made from these materials can be within this range for significant portions of the mission cycle, thus affording the possibility of a time-dependent mode of plasticity.

Unfortunately, the stress and temperature-dependence of this mode of deformation is not well understood yet – fact stated in some of the latest superalloys reviews [1]. For instance, a microtwinning mode of deformation has been identified [2] which seems to involve a twinning-type shear coupled with a diffusion-type shuffle of atoms in the 𝛾′ phase. Segregation of some elements to the microtwins has also been observed.

In this paper, a first attempt is made to build models for this coupled displacive/diffusional mode of deformation. Both semi-analytical and crystal plasticity type models are developed and compared. Our aim is to address some critical questions: (I) what are the kinetics of this mode? (II) How does they depend upon the temperature and stress? (III) What are the rate-controlling steps? (IV) What is the geometry of the microtwins and how do the dimensions involve? (V) How best to incorporate these ideas into constitutive models suitable for engineering design?

The modelling is compared critically with results on model single crystal and polycrystalline alloys, acquired with a new miniatured electro-thermal mechanical simulation device.

Keywords: microtwinning, superalloys, diffusion, plasticity, creep, modelling, phase transformations.

Refs. [1] R.C. Reed and C.M.F. Rae. Physical Metallurgy of the Nickel-Based Superalloys. Elsevier Ltd, 2014 [2] L. Kovarik, R.R. Unocic, J. Li, P. Sarosi, C. Shen, Y. Wang, and M.J. Mills. Microtwinning and

other shearing mechanisms at intermediate temperatures in Ni-based superalloys. Progress in Materials Science, 54(6):839–873, 2009


31

An Efficient Interphase Strength Evaluation of Fibre/Matrix Composite by Using Characteristic Length

Bentang A. Budiman*, Kosuke Takahashi, Kazuaki Inaba, Kikuo Kishimoto Department of Mechanical Sciences and Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo, 152-8550, Japan *[email protected]

Abstract: Studies on a region between a fibre and matrix composite mostly deduce that interphase can be formed on the manufacturing process. The interphase which is a three-dimensional thin layer has different mechanical properties from the fibre or matrix. Weak interphase causes ineffective stress transfer and micro defects which could cause poor performance of the composite as a load-bearing structure. On this study, an efficient evaluation of interphase strength (to) is proposed by introducing a characteristic length (Lt) in a stress contour which can be measured experimentally via photoelasticity. A relationship between to and Lt is expressed by an equation derived from the stress state in the matrix for an isolated single-fibre crack. Finite element analysis is then conducted in order to validate the equation. The analysis proves that the relationship can be approximated as a linear function. A single-fibre fragmentation test for carbon fibre-epoxy specimen is conducted to demonstrate Lt application for evaluating to. The Photoelastic technique is applied to capture a picture of the stress contour in the matrix. Several colours of the picture are then extracted to HSV values to form contours which are plotted in a graph (see Figure). Lt is then measured from the stress contours and an average interfacial strength of 22.1 MPa is successfully obtained.

Keywords: Interphase strength, fibre/matrix composite, stress contour.

Figure. Fibre crack on single-fibre fragmentation test (a) and plotted stress contours (b).


32

Surface Phase Transformation in Austenitic Stainless Steel Induced by Cyclic Oxidation in Humidified Air

Mattias Calmunger 1,*,Robert Eriksson 2, Guocai Chai 1,3, Sten Johansson 1, Johan J. Moverare 1

1. Department of Management and Engineering, Linköping University, 58183 Linköping, Sweden 2. Siemens AG, Huttenstr. 12, 10553 Berlin, Germany 3. AB Sandvik Materials Technology R&D Center, 81181 Sandviken, Sweden *[email protected]

Abstract: The formation of α' martensite at the surface of an AISI 304 stainless steel subjected to cyclic heating in humidified air is reported. The α' martensite formed during the cooling part of the cyclic tests due to local depletion of Cr and Mn and transformed back to austenite when the temperature again rose to 650 °C. The size of the α' martensite region increased with increasing number of cycles. Thermodynamical simulations were used as basis for discussing the formation of α' martensite. The effect of the α' martensite on corrosion is also discussed.

Keywords: Stainless steel, Thermal cycling, High temperature corrosion

Figure. ECCI-image of the microstructure after 10 thermal cycles between 100 °C and 650 °C in ~15 mol% water vapour. The image shows the effect of grain boundary diffusion of Cr, resulting in a thinner outer oxide layer (presumably Fe2O3) indicated by the three arrows at the α' martensite (BCC) regions. Above the α' martensite there is a Cr-rich (Cr, Fe)2O3 scale on the metal surface, compared to the inward growing oxides (presumably a Ni-rich (Cr, Fe, Ni)3O4 and a Ni-poor (Cr, Fe, Ni)3O4 spinel oxides) next to it.


33

Oxidation Behavior of a Single Crystal Ni-based Superalloy at Low Service Temperatures

Angelos Evangelou 1,*, Philippa Reed 1, Scott Lockyer 2, Katherine Soady 2 1. Department of Engineering and the Environment, University of Southampton, Highfield Campus,

Southampton, SO17 1BJ, UK 2. E.ON Technologies (Ratcliffe) Limited, Nottingham, NG11 0EG, UK *[email protected]

Abstract: The oxidation behavior of a single crystal Ni-based superalloy (CMSX-4) has been studied via Scanning Electron Microscopy image analysis (SEM) and Energy Dispersive Spectroscopy (EDS). These analyses have been carried out on the plan views and sections of the oxide scale produced by prolonged exposures in air at 550°C. The oxidation performance of the alloy was investigated under isothermal static exposure and isothermal exposure under a sustained, bending, load. The static oxidation kinetics has been assessed using mass change data from continuous thermo-gravimetric analysis and oxide scale thickness measurements from high magnification SEM images. The oxide scale was found to follow a sub-parabolic rate of growth (Figure 1) and broadly consisted of an outer NiO layer with an Al, Cr, Ti, Ta-rich oxide inner layer. Although there is some evidence of Al-rich oxide for the longer exposure times, it could not be concluded that the Al2O3 inner layer that is responsible for the higher temperature oxidation resistance had formed at these temperatures. Figure 2 shows SEM images of the morphology of the oxides produced under different stress levels. Oxides formed over high stressed regions were observed to develop internal protrusions up to 1.5μm deep. These protrusions mainly consisted of an Al, Re – rich oxide while a Ni, Co – rich oxide was generally observed to form above them.

Keywords: Oxidation, Ni-based superalloy.

Figure 1. Mass change data for CMSX-4 from isothermal testing at 550°C.

Figure 2. Effect of externally applied stress on the oxide scale morphology: A) Scale formed

over a plastically deformed region (high stress) with internal protrusions B) Scale formed over a low stress region

mailto:*[email protected]


34

Oxidation of Nickel-based Superalloys: Modelling & Validation

Yilun Gong 1,*, Henrik Larsson 2, Roger Reed 1, 3 1. Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK 2. Division of Materials Science and Engineering, KTH Royal Institute of Technology, Stockholm, SE-

10044, Sweden / Thermo-Calc Software AB, Sweden 3. Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, UK *[email protected]

Abstract: As conditions become ever more aggressive in the turbine, it is no longer the case that creep deformation alone controls component life; environmental effects such as oxidation and oxidation-assisted cracking are assuming greater importance. But quantitative, physics-based modelling of oxidation is rare.

In this poster, we will report progress made so far on the construction of computational models for oxide formation on Ni-Cr-Al system using coupled CALPHAD thermodynamic and diffusional kinetic approaches. Both cation and anion diffusion within each oxide phase are critically considered and assessed. The compositional-dependent oxidation kinetics are discussed.

Keywords: oxidation, thermodynamics, kinetics, CALPHAD

Figure. The outline of current models predicting the oxidation of nickel-based superalloys.


35

Ab Initio Study of the Effect of Solute Atoms on The Vacancy Diffusion in Ni-based Superalloys

Kamal Nayan Goswami*, Alessandro Mottura School of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK *[email protected]

Abstract: Ni-based superalloys find applications in the high temperature components of the jet turbine engines owing to their excellent properties under creep conditions. These properties are heavily influenced by altering the chemical composition in these alloys. In particular, the addition of small amounts of Re has been seen to dramatically improve the creep lives of Ni-based superalloys, such that this is sometimes referred to as the ‘Re effect’. The microstructure in these alloys consists of high volume fraction of a hard precipitate phase of cuboidal morphology embedded in a softer matrix phase. At high temperatures, the deformation in these alloys is restricted to the soft matrix phase and the creep dislocations cannot shear the precipitates. Gliding dislocations in the matrix phase have to climb at the interface for deformation to continue. Climb of dislocations is diffusion-controlled and depends on the absorption and emission of vacancies at the dislocation cores. Slow-diffusing solutes like Re are expected to hinder the diffusion of vacancies necessary for the dislocation climb. This hypothesis was tested in the present work from ab initio calculations using analytical formulations based on Manning’s random alloy model as well as kinetic Monte Carlo simulations to quantify the effect of solute elements on the vacancy diffusion coefficients (Dv) in Ni. Results from calculations within dilute limits suggest that slow-diffusing solute atoms do not reduce the diffusion of vacancies appreciably in these systems. Work is underway to investigate the effect in non-dilute regimes.

Keywords: Ni-based superalloys; Re-effect; Vacancy diffusion; Ab initio calculations; kinetic Monte Carlo simulations.

Figure. Vacancy diffusion coefficients at 1373 K as a function of solute concentration in Ni from kinetic Monte Carlo simulations.


36

Modelling and Analysis of Porous Core Material for Steel Laminates

Samuel Hammarberg Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, 971 87, Sweden. [email protected]

Abstract: In the modern society reduction of energy use is demanded in various sectors of the industry. Where the common goal is a sustainable society. One sector where this is in focus is the car industry, where lighter components can reduce energy consumption of vehicles. Thus, the manufacturing of lightweight car components is of great interest, and methods for creating these components are desirable.

In this work, the approach is to introduce steel laminates based on ultra-high strength thin steel sheets with a porous core to reduce weight. Initially the required conditions for simulating components subjected to crash loading are investigated. Furthermore the required conditions for simulating the forming of the component will be studied. Thus it is required in the project to bring forth a material model which can accurately predict forming of the porous material. This will be an important tool for future development of steel laminate components, and final use of the component in a vehicle structure.

If the goals of the project are reached it should be possible to reduce the weight of car components by up to 30 %. Which in its turn will reduce energy consumption of vehicles, thus leading to a more sustainable society.

Keywords: Steel laminates, lightweight, constitutive modelling.

.

Figure. Forming of laminate.


37

Effects of Ti/Nb Ratio on Nanoindentation Hardness in High Strength Ni-based Superalloys

Hiromu Hisazawa 1,*, Fauzan Adziman 2, David J Crudden2, David E.J. Armstrong3, Roger C Reed2 1. Department of Materials Science and Engineering, Tokyo Institute of Technology, 4259 J2-61

Nagatsuta-cho, Yokohama, 226-8502, Japan 2. Department of Engineering Science, University of Oxford, Woodstock Road, OX5 1PF, UK 3. Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK *[email protected]

Abstract: Age-hardening behaviours in high strength Ni-based superalloys ABD with varying Ti/Nb ratio have been studied by nanoindentation. ABD series alloys were developed with the aim of great balance of mechanical properties and oxidation resistance at high temperature. Superior mechanical properties use the large volume fraction of J’ precipitates, which make it sensitive to cooling condition in process of heat treatment. There is much of importance to evaluate mechanical property of the alloys varying composition with care of cooling rate. The alloys ABD-D2, D4, and D6 were studied. D2 contains the most Ti and D6 contains the most Nb with substitution on 1:1. They were cut into 2.5×2.5×1 mm3 small pieces to achieve temperature homogeneity, solution treated 30˚C above of J’ solvus and carefully cooled with rate 60 K/min. Aging treatment at 850 ˚C are followed up to 4 h. Nanoindentation test with strain rate between 0.001 and 1 show similar hardness and modulus but scattering at the early stage of indentation related to microscopic inhomogeneity, and stabilized at the last. The figure shows the change in the stabilized nanoindentation-hardness with following heat treatment. The hardness of all alloys once drops down with solution treatment and increase again with aging. ABD-D6 with the most Nb alloy shows the best aging-hardenability among the alloys studied. Nb is known as a better solution hardening element of J’ precipitate than Ti, however hardness need to be attributed to microstructure, which requires further observation to correlate hardness characteristics.

Acknowledgement: This research is a collaboration of University of Oxford and Tokyo Institute of Technology supported by Academy for Co-creative Education of Environment and Energy Science (ACEEES).

Keywords: superalloy, nanoindentation, heat treatment

Figure. Change in averaged nanoindentation hardness with following heat treatment in ABD alloys. They were averaged at the last stage of indentation.


38

10 m

Precipitation of GCP and TCP Phases at Grain Boundaries in Wrought Ni- base Alloys

Shuntaro Ida *, Satoru Kobayashi, Masao Takeyama Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, 2-12-1 Ookayama Meguro-ku, Tokyo 152-8550, Japan *[email protected]

Abstract: Wrought Ni base alloys are commonly strengthened by dispersion of coherent GCP (Geometrically Close-packed) precipitates such as Ni3Al-J' (L12) and Ni3Nb-J" (D022) within grain interiors. This strengthening method works for the materials that require relatively short-term high strength for jet engine components. However, this is not the case for landbase power components which require long-term creep rupture strength, and grain boundary design is definitely needed. In this study, we have first investigated the grain boundary precipitation behaviour of Ni3Nb-G phase (D0a), the poorest symmetry among GCP phases, at elevated temperatures by using model alloys of Ni-Nb-Fe system. The G phase preferentially nucleates on the grain boundaries at temperatures above the nose of the TTP curve. However, because of the distinct crystallographic orientation relationship with matrix ({111}J //(010)G, [110]J //<100>G), the phase grows toward the grain interiors. Thus, the average area fraction U of G phase is limited up to 75 %, depending on grain orientation. Therefore, TCP (Topologically Close-packed) phase such as Laves phase, which has more complex crystal structure, is more probable and promising for nucleation at grain boundaries. We will show you the results of the U by using Ni-Nb-Co ternary model alloys having Co2Nb (C15), together with G phase.

Keywords: Wrought Ni-based alloys, GCP phase, TCP phase.

Figure. BEIs of GCP Ni3Nb G phase on grain boundary aged at 1423 K/1 h in Ni-12Nb-3Fe.


39

Regeneration of Chitin using Conventional Organic Solvents and its Functional Gel Membrane

Yuri Iguchi 1,*, Tomokazu Iyoda 1,2, Keiji Nagai 1,2 1. Department of Innovative and Engineering Materials, Tokyo Institute of Technology, 4259-R1-25,

Nagatsuta, Midori-ku, Yokohama, Kanagawa 243-8506, Japan 2. Division of Integrated Molecular Engineering, Chemical Resources Laboratory, Tokyo Institute of

Technology,4295-S2 -3, Nagatsuta, Midori-ku, Yokohama, Kanagawa 243-8506, Japan *[email protected]

Abstract: Chitin, poly (N-acetyl glucosamine), is the principal ingredient of insect carapaces, and shells of crustaceans which accounts for the rigid structure due to the hydrogen bond between polymer chains. We investigated the mechanical property and the chemical reactivity of the regenerated chitin gel to utilise the gel as a functional membrane for applications such as a membrane catalyst. We regenerated chitin gel by using aprotic organic solvent and the mechanical properties and structure were examined. The chitin gel was highly transparent and its xerogel had layer structure. We found that the chitin gel crystallise after drying from powder-XRD analysis. From compression test, chitin gel had a breaking stress greater than 2.5MPa and breaking strain greater than 88%. The breaking stress of chitin gels differed depending on the solvent, the presence of a partition plate. These results above indicated the regenerated chitin gel has the anisotropic character after drying.

Keywords: Natural polymer, Chitin, Organogel, Organocatalyst, Membrane reactor, S-S curve.

Figure. Analysis of chitin gel.


40

Growth and Collapse of a Single Bubble near a Plate by Spark Discharge in Water

Akcam Inci*, Inaba Kazuaki, Takahashi Kosuke, Kishimoto Kikuo Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8550, Japan *[email protected]

Abstract: Establishing the interaction between the bubbly liquid and solid boundary is important in order to estimate flow profile and there have been many investigations on the bubble behaviour or bubble dynamics near solid boundaries Single bubble dynamics in the vicinity of a solid boundary submerged in water were studied experimentally. Single bubble inside a water tank was generated by a spark discharge of capacitor into a couple of copper wires closing a simple circuit. A circular polycarbonate plate was placed horizontally above the bubble creation site. Polycarbonate plates with two different thicknesses were tested by changing the distance between the plate and the creation site. The effects of distance to the wall and wall thickness on the bubble motion is observed by considering the fluid-structure interaction. It is shown that motion of the two boundaries during the bubble generation differ from each other. Jetting behaviour of two cases is also different. During the experiments, it is seen that direction of the jet is always away from the boundary for the water-air interface. For PC plate boundaries, jet changes its direction towards to the boundary as the stand-off parameter decreases. The value of stand-off parameter to change jet direction is around γ=1.80 and γ=1.20 for 2 mm and 1 mm thick circular plate, respectively. Considering this behaviour together with the different motion of the plates during the bubble generation, it can be said that fluid-structure interaction and plate flexibility plays an important role on collapse motion of the bubble.

Keywords: bubble, fluid-structure interaction, spark-discharge.


41

The Improving Graphene Transfer by Changing Transfer Variables

Yo Kan 1,2,*, Ella Carlsen-O'Conor 1, Adrian Murdock 1, Christian van Engers 3, Nicole Grobert 1 1. Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK 2. Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo, 152-8550, Japan 3. Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QZ, UK *[email protected]

Abstract: Graphene, a single atom thick layer of graphite with a honeycomb structure, possesses incredible electrical and physical properties which could be exploited in a wide range of future applications including faster transistors, flexible transparent conducting layers and more efficient solar cells. Chemical vapour deposition (CVD) is the most promising technique for producing large area sheets with high conductance as it is low cost, easily scalable, and readily controllable. However, one key problem that stands in the way of using CVD graphene is the need for transferring it from its synthesis substrate (e.g. Cu foil) to a target substrate (e.g. silicon wafers). While significant work has been conducted, for example bubbling transfer or electrochemical delamination, however, reliable transfer of CVD graphene is still an issue that needs resolving for graphene to be used in future applications.

We investigated the transfer of CVD graphene from copper foils to silicon wafers using polystyrene as a supporting layer. Graphene was synthesised using methane and hydrogen at an elevated temperature in a CVD system. The roughness of the copper foil was varied by using various etching methods and different foil purities. We varied the thickness of the polystyrene by spin-coating onto the graphene. In particular, for the most efficient transfer we suggest using thinner polystyrene and smoother copper foil. Further investigations into the roughness of silicon support are also planned for the future. Improving our understanding of graphene transfer will hopefully bring us closer to harnessing its exceptional properties for use in future devices.

Keywords: graphene, transfer, polystyrene, carbon, CVD, conductance, Si wafer.

Figure. Graphene transfer method from Cu substrate to Si wafer


42

Wave Propagation across Solid-Fluid Interface with Fluid-Structure Interaction

Tomohisa Kojima*, Kazuaki Inaba, Kosuke Takahashi, Kikuo Kishimoto Department of Mechanical Sciences and Engineering, Tokyo Institute of Technology, 2-12-1-16-5 Ookayama, Meguro-ku, Tokyo, 152-8550, Japan *[email protected]

Abstract: Fluid-structure interaction is one of the most important phenomena to be clarified and controlled in many industrial fields. In some problems, interaction mechanism strongly depends on wave propagation across the interface of solid and fluid. Although many studies have been conducted about fluid-structure interaction, the mechanism of wave propagation close to the solid-fluid interface remains unclear. Our aim is to clarify the mechanism of wave propagation across the solid-fluid interface with fluid-structure interaction and develop the theoretical model to explain this phenomenon. In this study, we investigated the relation between the structural movement and incident / transmitted / interfacial pressure waves on the solid-fluid interface. The results of the experiments indicated that averaged interface pressure can be estimated by the Joukowsky equation substituting interface velocity derived from the impact problems of two rigid bodies with fluid’s momentum. It was also confirmed that under some conditions, cavitation bubbles appeared on the interface so that the continuity assumption of the interface may not be valid.

Keywords: fluid-structure interaction, impact, elastic-waves, propagation.

Figure. Strain histories.


43

The Effect of Boron on Grain Boundary Character in a New Polycrystalline Superalloy

Paraskevas Kontis 1,*, Hanis A. Mohd Yusof 1, Stella Pedrazzini 1, Katie L. Moore 2, Paul A.J. Bagot 1, Michael P. Moody 1, Chris R.M. Grovenor 1, Roger C. Reed 1 1. Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK 2. University of Manchester, Alan Turing Building, Oxford Road, Manchester, M13 9PL, UK *[email protected]

Abstract: The role of boron in conferring the grain boundary character in a new polycrystalline superalloy suitable for power generation applications is considered. One boron-free and three boron-containing variants are studied using a suite of high resolution characterisation techniques including atom probe tomography (APT), secondary ion mass spectroscopy (SIMS) and transmission electron microscopy (TEM). The primary effect of boron addition is the suppression of Cr-rich M23C6 carbide and the formation instead of the Cr-rich M5B3 boride. The SIMS analysis indicates that the boride particles are distributed uniformly along the grain boundaries, of length up to 500nm along the grain boundary and thickness 300nm normal to it. The substantial majority of the boron added resides in the form of the M5B3 boride; some boron segregation is found at the γ'/M5B3 interfaces but interfaces of other forms such as γ/M5B3, γ/MC and γ'/MC are not prone to segregation in this way. Creep testing indicates that the optimum boron content in this alloy is 0.05 at.%.

Keywords: nickel-based superalloys, grain boundaries, borides, mechanical properties.


44

A Study on Si Surface Flattening Process and its Effect on Device Characteristics

Sohya Kudoh*, Shun-ichiro Ohmi** Department of Electronics and Applied Physics, Tokyo Institute of Technology, J2-72, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502, Japan *[email protected];**[email protected]

Abstract: As the scaling down of Metal–Insulator–Semiconductor Field-Effect Transistor (MISFET) which is important for electric devices (e.g. mobile phone and computer), the interface flatness of the gate insulator/Si will significantly affect the device performance. It is well known that carrier scattering caused by roughness at the gate insulator/Si interface degrades the carrier mobility [1]. Furthermore, the interface roughness degraded the reliability and increased the gate leakage current [1,2]. Even for high-k gate insulator which is necessary for further scaling, the roughness at high-k/Si interface significantly affects the MISFET characteristics [3,4]. It has been reported that flat Si surface is able to be obtained by annealing or sacrificial oxidation. Furthermore, the atomically flat surface of Si(100) is able to be obtained by annealing in Ar or H2 ambient. To obtain atomically flat Si surface by sacrificial oxidation process, oxidation mechanism at SiO2/Si interface must be clarified. However, the mechanism of sacrificial oxidation method has not been clearly explained. In my research, I have investigated the effect of the sacrificial oxidation for Si surface roughness to clarify the mechanism, and its effect on electrical characteristics of MIS diodes. By the etching of the 100 nm-thick sacrificial oxide formed by thermal oxidation at 1100 degrees Celsius, the surface Root-Mean-Square (RMS) roughness of Si substrate was reduced from 0.22 nm to 0.07 nm. Moreover, it has been revealed that the electrical reliability, evaluated by time-dependent dielectric breakdown (TDDB) measurement, was dramatically improved by reducing Si surface roughness.

Keywords: Si surface roughness, oxidation process, MIS diode, reliability.

Figure. Reliability of MIS diodes dependence on flattening process.

Acknowledgements The authors would like to thank Mr. N. Hatakeyama and Mr. M. Suzuki of Tokyo Institute of Technology for their support for this research. The authors also thank Prof. Emeritus T. Ohmi and Dr. T. Suwa of Tohoku University, Dr. M. Shimada and Mr. I. Tamai of JSW-AFTY for their support and useful discussions for this research.

References

[1] R. Kuroda, et al., IEEE Trans. Electron Devices., 56, pp. 291-298, 2009. [2] T. Ohkawa, et al., IEEE Trans. Electron Devices., 48, pp.2957-2959, 2001. [3] S. Ohmi, IEICE Electron. Exp., 11, No.14, 20142006, 2014. [4] S. Ohmi, et al., IEEE Trans. Semicond. Manuf. 28, No.3, pp.266-271, 2015.


45

The Development of New Co-Ni Superalloys

Paul Mulvey 1,*, Mark Hardy 2, David Dye 1 1. Department of Materials, Imperial College London, Prince Consort Road, London, SW7 2BP, UK 2. Rolls Royce Plc, Derby, DE24 8BJ, UK *[email protected]

Abstract: In 2006 Sato et al discovered that cobalt based superalloys with a stable L12 gamma prime phase were viable using the Co3(Al,W) system. There is now an on-going effort to develop these alloys with the aim of increasing engine operating temperatures compared to the current capabilities of nickel based superalloys. V208C & V208D are Co-Ni superalloys, with nominal compositions of 36Co-35Ni-15Cr-10Al-3W-1Ta and 40Co-29Ni-17Cr-10Al-3W-1Ta (at%) respectively, produced by hot isostatic pressing and subsequent forging. Both alloys have displayed extremely stable secondary gamma prime after 2000 hours at 800°C with an insignificant degree of coarsening. A combined post-forging heat treatment has been developed firstly to provide initial stabilisation of the gamma prime phase and secondly to form serrated grain boundaries. The thermal stability and ability to form serrated grain boundaries shows great promise for the temperature capabilities and creep performance of these alloys.

Keywords: Cobalt, Superalloy, Heat-treatments.

Figure. Example of a serrated grain boundary achieved with heat treatment.


46

Microstructures and Mechanical Properties of ZrC-added Mo-Si-B alloys

Shunichi Nakayama*, Kyosuke Yoshimi Department of Materials Science, Tohoku University, Sendai, Miyagi, 980-8579, Japan *[email protected]

Abstract: Recently, our research group has newly developed TiC-added Mo-Si-B alloys for ultra-high temperature structural applications. In the alloys, the drawbacks of Mo-Si-B ternary alloys that are relatively high density (~9.5 g/cm3) and poor room-temperature fracture toughness have been improved without impairing high-temperature strength. However, understandings why the material properties of the Mo-Si-B-based alloys are improved by the TiC addition has not advanced yet. Systematic studies are needed to get understandings on carbide-added Mo-Si-B alloys. In this study, ZrC is added to Mo-Si-B alloys and the microstructure and mechanical properties of ZrC-added Mo-Si-B alloys are systematically investigated. Several kinds of ZrC-added Mo-Si-B alloys were prepared by a conventional arc-melting, and heat-treatment at 1800°C for 24 h in an Ar atmosphere was carried out. After heat-treatment, constituent phases in the alloys were Mo solid solution (Moss), Mo5SiB2 (T2), ZrC and/or Mo2B. The density of the alloys measured using the Archimedes’ principle was in the range of Ni-based superalloys. High-temperature compression tests at 1400°C and four-points bending tests with a Chevron notch at room temperature were conducted to investigate their mechanical properties. It was found that high-temperature strength depends on T2, Mo2B and ZrC volume fractions. On the other hand, room-temperature fracture toughness depends on not only Moss volume fraction but also ZrC volume fraction. Therefore, it was strongly suggested in this study that ZrC plays important roles to provide both high-temperature strength and fracture toughness in the Mo-Si-B-based alloys. Carbide-added Mo-Si-B-based alloys will show better structural performance by optimizing composition and microstructure.


47

Intergranular Fracture at 800 deg C in Advanced Nickel-based Superalloys

Andre A.N. Nemeth*, David J. Crudden, David E.J. Armstrong, Roger C. Reed

Department of Materials, University of Oxford, Park Rd, Oxford, OX1 3PH, UK *[email protected]

Abstract: There is significant interest in defining and quantifying the mechanical performance of polycrystalline superalloys particularly high strength ones produced by powder processing at temperatures of 800 deg C for turbine disc applications. In part, this is because the outer rims of a turbine disc, where the locating features for turbine blades can experience such temperatures during some portion of the mission cycle. In this work, an electro-thermal-mechanical testing (ETMT) system is employed which is capable of the rapid assessment of the mechanical properties of commercial superalloys at 800 deg C on an intermediate length scale; it makes use of miniature testpieces with a very small cross-section of 1x1 mm. Uniaxial test results from miniaturised tests were found to be in close agreement to conventional full-scale tests. This finding confirms that the used miniaturized testpieces are of sufficient size to characterise certain bulk material properties. Miniaturised tests were then applied to study a turbine disc relevant problem: intergranular oxidation-assisted cracking. Brittle intergranular failure of a uniaxial test was achieved at 800 deg C by using a slow strain-rate of 0.0001 /s. To interpret the slow strain-rate test results and to correlate them to effects on the micro-scale, the ETMT testpieces were further characterised by the preparation of microcantilevers which allowed the strength of the grain boundary to be assessed. This suite of experimental tools on a small length scale when combined with high resolution characterisation techniques allow the composition-dependence of the mechanical properties to be elucidated.

Keywords: Electro-thermal mechanical testing; Nanoindentation; Superalloys; Fracture.


48

Lifetime Estimation of Heavy-Vehicle Engine Materials

Viktor Norman 1,*, Peter Skoglund 1,2, Johan Moverare 1 and Daniel Leidermark 3 1. Division of Engineering Material, Linköping University, SE-58183 Linköping, Sweden 2. Scania CV AB, Materials Technology, SE-15187 Södertälje, Sweden 3. Division of Solid Mechanics, Linköping University, SE-58183 Linköping, Sweden *[email protected]

Abstract: The demands on newly produced heavy-vehicles expressed by the market and by the society at large are constantly increasing. In particular, the European Union recurrently formulates new emission standards to limit the European exhaust emission, which in turn dictates the lowest acceptable limit of the engine efficiency. Consequently, future engines are expected to operate at higher combustion pressures and temperatures, which will require significant measures to avoid the reduction of the engine lifetime. This has called for more time-efficient and sophisticated design methods, based on finite element and lifetime assessment modelling rather than prototype testing. Accordingly, the purpose of this study is to develop a lifetime assessment model for engine materials, which is capable of estimating the effect of superimposed vibrational (HCF) loads. To this end, the present study has investigated the fatigue life of laboratory specimens subjected to typical engine load conditions; tests denoted as combined thermo-mechanical and high-cycle fatigue (TMF-HCF) tests. The studied materials are those commonly employed in different engine components, namely EN-GJL-250, EN-GJV-400 and EN-GJS-SiMo5-1. It is demonstrated that all materials follow a consistent pattern involving a material-dependent threshold, when subjected to an increasing HCF load, see the figure below. In addition, the developed model manages well to predict this trend. The model is based on Paris law where the crack length is interpreted as an average length of many small microcracks. It is also assumed that the crack mechanism is the same in the TMF and HCF cycle.

Keywords: Cast iron, Thermo-mechanical fatigue, High-cycle fatigue, Fatigue crack growth, Life prediction.

Figure. The effect of the HCF strain range on the fatigue life of EN-GJV-400 compared with the model.


49

Thermo-mechanical Characterization of a Nickel-based Superalloy

Lluís Pérez Caro 1,2,*, Eva-Lis Odenberger 1,2,**, Per Thilderkvist 1,***, Mats Oldenburg 2,**** 1. Forming Group OSAS, Industrial Development Centre in Olofström AB, Vällaregatan 30,

Olofström, SE-293 38, Sweden 2. Division of Solid Mechanics, Luleå University of Technology, University campus - Porsön, Luleå,

SE-971 87, Sweden *[email protected] **[email protected] ***[email protected] ****[email protected]

Abstract: Nickel-based superalloys are often used in the hot sections of gas turbine engines for both military and civil aircrafts due to their mechanical and chemical stability under extreme conditions i.e. high temperatures, for a long time. In order to save weight and, thereby, reduce fuel consumption and carbon dioxide emissions, each part of load carrying structures is made of the most suitable material state, such as sheet metal parts, small ingots and forgings assembled by welding. High-tech companies have implemented FE-analysis to model the whole process chain to improve, identify and solve problem areas in an early stage while minimizing try-outs and modifications in the manufacturing processes or tooling. However, it is necessary to provide highly accurate data about material, boundary conditions and process parameters. In this study, uniaxial tensile tests in Alloy 718 were carried out at different temperatures up to 900°C in order to provide input data for forming simulations in LS-DYNA. The heating of the samples was done using inductive heating, while the strains on the specimens were measured using ARAMIS. Dynamic Strain Aging (DSA) appeared between 300°C and 700°C always followed by an audible acoustic emission, which suggests that type C serrations were present. The results show a decreasing yield stress yet preserved Lankford coefficients while increasing the temperature. The combination of both high temperature and serrations demands the development of a sustainable speckled pattern in order to prevent its progressive loss during the experiments.

Keywords: FE-analysis, Alloy 718, Dynamic Strain Aging, high temperature.

Figure. Hardening curves of Alloy 718 at room temperature and 500°C.


50

Material Characterisation for Containment Dimensioning

Ted Sjöberg 1,*, Jörgen Kajberg 1, Mats Oldenburg 1 1. Division of Mechanics of Solid Materials, Luleå University of Technology, SE-97187 Luleå, Sweden *[email protected]

Abstract: Increasingly tough environmental goals, such as the ones set up by the clean sky joint undertaking, are being put on aircrafts in order to reduce emissions. This is leading aeronautics manufacturers to push materials and structures closer to their limits in order to increase efficiency and save weight. GKN Aerospace has declared that they will reduce the weight of their structural engine components by 20%. At the same time the structural components have to retain their containment capability; that is to prevent damage to the surrounding structure in the event of released parts in a blade out event. Hence, good knowledge in the areas of plastic deformation and failure, especially at high strain rates and elevated temperatures are of great importance.

As part of an on-going research collaboration between GKN Aerospace and Luleå University of Technology a methodology to characterise material at conditions closer to service condition has been developed. Specimens of nickel super alloy 718 have been tested up to strain rates of 1000s-1 by using a high speed tensile testing machine. In order to also test the material at temperatures up to 650 ˚C the machine has been equipped with an induction heater. Using standard uniaxial tensile test it is possible to evaluate the stress-strain relation only up to localisation. To determine the full stress-strain relation all the way to failure a method using digital speckle photography to capture the local strain field in order to calculate a piecewise-linear hardening curve from the global equilibrium equation has been developed at LTU. One further advantage of using this method is the possibility to get the true stress – true strain relation in specimens with geometries undergoing non-uniform deformation.

Figure. a) picture from DSP-measurements showing local strain field b) hardening curves showing the much higher strains reached by using DSP-based evaluation

Acknowledgements: This project is performed at Luleå University of Technology in collaboration with GKN Aerospace, Trollhättan. Economic support is supplied by VINNOVA through the NFFP6 project nr 2013-01155.


51

Fabrication of Al-Cu/pure Al Clad Strips by Vertical-type Tandem Twin-roll Casting

Tomomi Sugiyama 1,*, Yusuke Takayama 1, Yohei Harada 1, Shinji Kumai 1 1. Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, Ookayama, Tokyo,

152-8552, Japan *[email protected]

Abstract: Clad materials consist of layers of different materials which can combine beneficial bulk properties of one material with advantageous layer properties of another. Vertical-type tandem twin-roll casting is a novel method of fabricating aluminium alloy clad strips and can produce three layered clad strips from molten metals directly. It use two vertical-type twin-roll casters arranged vertically. Figure is a schematic diagram of this method for three-layered clad strips. A core layer is fabricated by the first twin-roll, lead into the second roll gap and sanded by solidification shells of clad layers growing from surface of second twin-roll. This method can reduce processing time and steps compared to the conventional one and has some additional merits. Previous studies showed that Al-Mn/Al-Si alloy clad strips, which are widely used as automotive brazing sheets, can be fabricated by this method, but other kinds of clad strips had not been reported. Consequently, Al-Cu/pure Al clad material used in airplane bodies was focused on and its fabrication was attempted. Since the melting temperature of clad is higher than the solidus temperature of core, it was said to be difficult to be made by this method. As a result, continuous three-layered clad strips had been fabricated successfully. However, because of high temperature of clad molten metal and decreasing of cooling ability of rolls during the casting, at the centre of core, solidification was not completed even after the strip passed the final cooling point. Therefore further study especially about cooling ability of rolls is still needed.

Keywords: clad material, twin-roll casting, aluminium alloy.

Figure. A schematic diagram of vertical-type tandem twin-roll casting for three layered clad strips.


52

Effect of Strain Rate and Grain Diameter on Local Deformation Energy of Industrial Pure Iron

Yuji Takeda 1,*, Masatoshi Aramaki 2, Osamu Furukimi 2, Rintaro Ueji 3, Takashi Muzuguchi 4

1. Department of Material Processing Engineering, Kyushu University 2. Department of Materials Science and Engineering, Kyushu University 3. Joining and Welding Research Institute, Osaka University 4. Faculty of Engineering, Kagawa University *[email protected]

Abstract: The effects of strain rate (10-3-103/s) and the grain diameter (60 and 169μm) on the deformation energy of industrial pure iron were investigated by using of load sensing block type testing machine to revealed the basic knowledge for the increase of the energy absorption. We used the specimen with gauge length of 6 mm because of the characteristics of the testing machine. The deformation energy which is the factors for the increase of energy absorbed in the collision was estimated by the area of load-displacement curves. Figure 1 shows that the local deformation energy after the maximum load was increased with the strain rate in the region from 10-3/s to 10-1/s. This increase of the local deformation energy was caused by the increase of dislocation movement velocity and void growth behavior by high strain rate. The increase of the grain diameter also caused the increase of the local deformation energy. The coarsening of grain diameter increased the ligament length of the voids generated from grain boundaries. These results suggested that large ligament length causes the large local deformation energy. On the other hand, the effect of the grain diameter on the uniform deformation energy was not observed. From these results, it was revealed that the increase in grain diameter of steel is effective to improve the energy absorption property.

Keywords: vehicle collision, strain rate, grain diameter, local deformation energy, industrial pure iron, tensile test, load-displacement curves, dislocation, voids, grain boundary.

Figure. Relationships between local deformation energy and strain rate, grain diameter for industrial pure iron.


53

Synthesis of Well-defined Functional Polymer Particles by Living Dispersion Coordination Polymerization of Allene Derivatives

Akira Yamauchi 1,*, Takayuki Omura 2, Yoshiyuki Oguchi 2, Hiroshi Yamauchi 2, Hiroki Nishiyama 1, Shinsuke Inagi 1, and Ikuyoshi Tomita 1 1. Department of Electronic Chemistry, Tokyo Institute of Technology, Nagatsuta-cho 4259-G 1-9,

Midori-ku, Yokohama 226-8502, Japan 2. Sekisui Chemical Co., Ltd. Hyakuyama 2-1, Shimamoto-cho, Mishima-gun, Osaka 618-0021, Japan *[email protected]

Abstract: Monodispersed polymer particles are attractive materials for a wide range of advanced applications. Recently, we have reported that the -allylnickel-catalyzed coordination polymerization of various allene derivatives proceeds in a living fashion also in protic polar media1) and polymer particles with narrowly dispersed diameter distribution can be produced under the dispersion polymerization conditions. In this paper, we describe the living dispersion sequential copolymerization using comonomers having various functional groups such as substituted allenes and substituted acetylenes to obtain well-defined functionalized polymer particles (Scheme 1). As a typical example, the dispersion polymerization of phenoxyallene (1, 100 equiv) was performed at ambient temperature in EtOH. As a result, 1 was consumed quantitatively within several hours to give a suspension of “living” polymer particles. Then, an OH-substituted allene monomer (2, 20 equiv), an OH-substituted acetylene monomer (3, 20 equiv), or a bisallene (4, 20 equiv), was added and the post-polymerization was performed until the second monomer (2-4) consumed completely. The obtained polymer particles proved to have narrowly dispersed diameter distribution as confirmed by SEM observations. The post-polymerization of various allene and acetylene derivatives and the applications of the well-defined functional polymer particles are also described.

Keywords: Allene Derivatives, Living Dispersion Coordination Polymerization, Polymer Particles.

Reference 1) T. Kino, M. Taguchi, A. Tazawa, and I. Tomita, Macromolecules, 39, 7474-7478 (2006).

Ni

OCOCF3

PPh3

OPh•

PVPEtOH

CuI

•

O

O

••

Cross-linked

Functionalized by acetylene derivatives

Functionalized by allene derivatives

Scheme 1.

HO

OH

2

4

3

Living polymer particles

1


54

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In-situ Tensile Deformation Behaviour near Grain Boundary with and without Laves Phase in Novel Fe-Cr-Ni-Nb Steels at 1073 K

Mari Yoshihara*, Masao Takeyama Department of Metallurgy and Ceramics Science, Graduate School of Science and Engineering, Tokyo Institute of Technology, S8-8 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552, Japan *[email protected]

Abstract: A novel austenitic heat resistant steel of Fe-20Cr-30Ni-2Nb (at.%) exhibits excellent creep rupture strength superior to any other conventional steels and comparable to wrought Ni-base superalloys (IN617) at 1073 K. This superior strength is due to the decoration of grain boundaries by Fe2Nb TCP Laves phase with the area fraction (ρ) higher than 80 %. This strengthening method is called “Grain Boundary Precipitation Strengthening (GBPS)”. Our previous research revealed highly misoriented subgrains formed near the grain-boundary region with no Laves phase particles on the grain boundaries, and suggested that GB Laves phase suppresses accelerated local deformation during creep, thereby leading to the excellent strength. Based on those results, Tarigan et al. proposed a model on GBPS mechanism by taking the local misorientation into account. However, due to a lack of initial orientation, this model is not sufficient to evaluate the local deformation. In this study, unique attempt has been made to detect microstructural and orientation change around grain boundary decorated with and without Laves phase accurately, in terms of newly designed in-situ tensile test machine operable at 1073K in SEM chamber. The specimen with a gauge portion of 14x3x1 mm was tested at a strain rate of 8x10-4 /s up to a plastic strain of 0.1. The in-situ EBSD analysis (Figure) clearly detected highly misoriented regions with respect to the initial grain orientation, along the uncovered grain-boundary region, even under relatively higher strain rates. The highly misoriented region becomes more obvious, depending on grain orientations with respect to loading axis.

Keywords: In-situ observation, grain-boundary precipitation strengthening.

Figure SEIs and corresponding GROD maps showing the orientation change near grain boundarie during in-situ tensile test at 1073 K; (a) (c) before and at (b) (d) plastic strain of 0.1. The support of the Grant-in-Aid (JY220215) on Advanced Low Carbon Technology Research and Development Program (ALCA), Japan Science and Technology Agency (JST) is gratefully acknowledged.


55

Sponsors

Symposium secretariat

Technical and on-site enquiries:

Dr Fauzan Adziman

Department of Engineering Science University of Oxford

Begbroke Science Park Begbroke Hill

Woodstock Road Oxfordshire, OX5 1PF, UK Tel: +44 (0)1865 613076

Email: [email protected]

General enquiries:

Mrs Karen Bamford

Department of Engineering Science University of Oxford

Begbroke Science Park Begbroke Hill

Woodstock Road Oxfordshire, OX5 1PF, UK Tel: +44 (0)1865 613450

Email: [email protected]

Symposium venue: Pembroke College,

Oxford, UK

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