Chapter 11 -
Reminders
Exam II: Wednesday March 25th
Quiz: Wednesday March 18th
Material: Chapters 6 - 10
1
Chapter 11 -
ISSUES TO ADDRESS...
Chapter 11: Applications and Processing of Metal Alloys
How are commercial alloys classified and what are their common applications? What are some of the common fabrication techniques
for metals? How do they alter the properties? What heat treatment procedures are used to improve the
mechanical properties of both ferrous and nonferrousalloys?
2
Chapter 11 -Fig_11-1
Chapter 11 -
How much steel is produced in the US?
A. 5,000 metric tonsB. 100,000 metric tonsC. 1 million metric tonsD. 5 million metric tonsE. 100 million metric tons
Chapter 11 -
Chapter 11 -americanresources.org
Chapter 11 -
World primary Titanium sponge production volumes increased by 11% to 222 thousand tons in 2013 compared with production in 2012. New production capacities are to be introduced by Ukraine and Canada. Commercial aerospace industry supports the market with high demand for titanium. In Singapore, on the contrary, a TiO2 plant was closed in 2013 due to high prices and sluggish distribution channels.
http://mcgroup.co.uk/researches/titanium
Chapter 11 -
Wide spread use of steel due to:
iron-containing compounds are abundantin the Earths crust
Relatively economical extraction, refining, alloying and fabrication
Ferrous alloys are extremely versatile
Disadvantage: corrosiondensity
Sao Francisco Craton, Minas Gerais, Brazil8
Chapter 11 -
Chapter 11 -
Chapter 11 -
Adapted from Fig. 11.1, Callister & Rethwisch 9e.
Classification of Metal AlloysMetal Alloys
Steels
Ferrous Nonferrous
Cast Irons
Chapter 11 -Based on data provided in Tables 11.1(b), 13.2(b), 11.3, and 11.4, Callister & Rethwisch 9e.
SteelsLow Alloy High Alloy
low carbon
Chapter 11 -
Ferrous AlloysIron-based alloys
Nomenclature for steels (AISI/SAE)10xx Plain Carbon Steels11xx Plain Carbon Steels (resulfurized for machinability) 15xx Mn (1.00 - 1.65%)40xx Mo (0.20 ~ 0.30%)43xx Ni (1.65 - 2.00%), Cr (0.40 - 0.90%), Mo (0.20 - 0.30%)44xx Mo (0.5%)
where xx is wt% C x 100example: 1060 steel plain carbon steel with 0.60 wt% C
Stainless Steel >11% Cr
Steels Cast Irons
13
PresenterPresentation NotesSAE: Society of automotive engineersAISI: The American Iron and Steel Insititute
Chapter 11 -
Ferrous Alloys:Advanced High Strength Steels (AHSS)
AISI: www.steel.org (2006)14
PresenterPresentation NotesSAE: Society of automotive engineersAISI: The American Iron and Steel Insititute
Chapter 11 -
Typical: C: 0.05 - 0.15 Mn: 1.0 2.0Others: Si, Cr, Ni, Mo, Nb, V
0.15C, 1.5 Mn, 1.5 SiWQ from 775oC
V 9 %; C 0.45
V 30 %; C 0.17
C = 0.06
810 oC
750 oC
A.De et al. Adv. Mat. Proc. 2003
Dual Phase Steels
Ferrite-martensitemicrostructures
Chapter 11 -
Davies (1978)
Strengthening in DP Steels
Strength increase follows rule of mixtures for composites: T = Vff + VMM
16
Chapter 11 -
Cast Irons Ferrous alloys with > 2.14 wt% C
more commonly 3 - 4.5 wt% C Low melting relatively easy to cast Generally brittle Cementite is a metastable compound, it can
decompose to ferrite + graphiteFe3C 3 Fe () + C (graphite)
generally a slow process
17
PresenterPresentation NotesSo phase diagram for this system is different (Fig 12.4)
Chapter 11 -
Fe-C True Equilibrium Diagram
Graphite formation promoted by
Si > 1 wt%
slow cooling
Fig. 11.2, Callister & Rethwisch 9e.[Adapted from Binary Alloy Phase Diagrams, T. B. Massalski (Editor-in-Chief), 1990. Reprinted by permission of ASM International, Materials Park, OH.]
1600
1400
1200
1000
800
600
4000 1 2 3 4 90
L
+L
+ Graphite
Liquid +Graphite
(Fe) C, wt% C
0.65
740C
T(C)
+ Graphite
100
1153CAustenite 4.2 wt% C
+
18
PresenterPresentation NotesCast irons have graphite
Chapter 11 -
Types of Cast IronGray iron graphite flakes gray fracture surface weak & brittle in tension stronger in compression excellent vibrational dampening wear resistantDuctile (or Nodular) iron add Mg and/or Ce graphite as nodules not flakes matrix often pearlite or ferrite Valves, pump bodies,
crankshafts, gears.
Figs. 11.3(a) & (b), Callister & Rethwisch 9e.[Courtesy of C. H.Brady and L. C. Smith,National Bureau ofStandards, Washington,DC (now the NationalInstitute of Standardsand Technology, Gaithersburg, MD]
19
PresenterPresentation NotesCe: cerium
Chapter 11 -
Production of Cast Irons
Fig.11.5, Callister & Rethwisch 9e.(Adapted from W. G. Moffatt, G. W. Pearsall, and J. Wulff, The Structure and Properties of Materials, Vol. I, Structure, p. 195. Copyright 1964 by John Wiley & Sons, New York. Reprinted by permission of John Wiley & Sons, Inc.)
20
Chapter 11 -
Types of Cast Iron (cont.)
White iron < 1 wt% Si pearlite + cementite very hard and brittle Fracture surface:
white appearance
Malleable iron heat treat white iron at 800-900 C graphite in rosettes within ferrite matrix reasonably strong and ductile
Figs. 11.3(c) & (d), Callister & Rethwisch 9e.
Courtesy of A
mcast Industrial C
orporation
Reprinted w
ith permission of the
Iron Castings Society, D
es Plaines, IL
21
Chapter 11 -
Types of Cast Iron (cont.)Compacted graphite iron graphite nodules and flakes some Mg or Ce added but less than
used in nodular cast irons relatively high thermal conductivity good resistance to thermal shock lower oxidation at elevated
temperatures diesel engine blocks
Fig. 11.3(e), Callister & Rethwisch 9e.
Courtesy of Sinter-C
ast, Ltd.
22
Chapter 11 -
Limitations of Ferrous Alloys
1) Relatively high densities2) Relatively low electrical conductivities3) Generally poor corrosion resistance
23
Chapter 11 -
Classification scheme for nonferrous alloys
Fig. 11.6
24
Chapter 11 -Based on discussion and data provided in Section 11.3, Callister & Rethwisch 9e.
Nonferrous Alloys
NonFerrous Alloys
Al Alloys-low : 2.7 g/cm3-Cu, Mg, Si, Mn, Zn additions -solid sol. or precip.
strengthened (struct. aircraft parts)
Mg Alloys-very low : 1.7g/cm3- Powder ignites easily - Steering wheel, laptop
Refractory metals-high melting Ts-Nb, Mo, W, Ta Noble metals
-Ag, Au, Pt -oxid./corr. resistant
Ti Alloys-relatively low : 4.5 g/cm3
vs 7.9 for steel-reactive at high Ts-space applic.
Cu AlloysBrass: Zn is subst. impurity(costume jewelry, coins)
corrosion resistant)
Bronze : Sn, Al, Si, Ni are subst. impurities(stronger,
(bushings)
Cu-Be: precip. hardened for strength
25
PresenterPresentation NotesBushing,Landing gear Pt - platinum
Chapter 11 -Table. 11.7
Temper Designation Scheme for Aluminum Alloys
Aluminum (Al) alloys are classified as either cast or wrought. Cast Al alloys: e.g., 295.0, 356.0 Temper designation indicates the mechanical and/or heat treatment the alloy
has been subjected to.
26
Chapter 11 -
Metal Fabrication How do we fabricate metals?
Example: Steelmaking
Extract metal from ore https://www.youtube.com/watch?v=9l7JqonyoKA
Recycling through scrap remelting https://www.youtube.com/watch?NR=1&v=T1CJ5NP
W8MU&feature=endscreen
27
Chapter 11 -
Metal Fabrication How do we fabricate metals?
Blacksmith - hammer (forged) Cast molten metal into mold
Forming Operations Rough stock formed to final shape
Hot working vs. Cold working Deformation temperature
high enough for recrystallization
Large deformations
Deformation belowrecrystallization temperature
Strain hardening occurs Small deformations
28
Chapter 11 -
FORMING
roll
AoAd
roll
Rolling (Hot or Cold Rolling)(I-beams, rails, sheet & plate)
Ao Ad
force
dieblank
force
Forging (Hammering; Stamping)(wrenches, crankshafts)
often atelev. T
Adapted from Fig. 11.9, Callister & Rethwisch 9e.
Metal Fabrication Methods (i)
ram billet
container
containerforce die holder
die
Ao
Adextrusion
Extrusion(rods, tubing)
ductile metals, e.g. Cu, Al (hot)
tensile force
AoAddie
die
Drawing(rods, wire, tubing)
die must be well lubricated & clean
CASTING MISCELLANEOUS
29
Chapter 11 -
FORMING CASTING
Metal Fabrication Methods (ii)
Casting- mold is filled with molten metal metal melted in furnace, perhaps alloying
elements added, then cast in a mold common and inexpensive gives good production of shapes weaker products, internal defects good option for brittle materials
MISCELLANEOUS
30
Chapter 11 -
Sand Casting(large parts, e.g.,auto engine blocks)
Metal Fabrication Methods (iii)
What material will withstand T >1600Cand is inexpensive and easy to mold?
Answer: sand!!!
To create mold, pack sand around form (pattern) of desired shape
Sand Sand
molten metal
FORMING CASTING MISCELLANEOUS
31
Chapter 11 -
Metal Fabrication Methods (v)
Continuous Casting-- simple shapes
(e.g., rectangular slabs, cylinders)
molten
solidified
FORMING CASTING MISCELLANEOUS
Die Casting-- high volume-- for alloys having low melting
temperatures
https://www.youtube.com/watch?v=BX8w-GUPz1w
Investment Casting:
32
Chapter 11 -
MISCELLANEOUSCASTING
Metal Fabrication Methods (vi)
Powder Metallurgy(metals w/low ductilities)
pressure
heat
point contact at low T
densificationby diffusion at higher T
area contact
densify
Welding(when fabrication of one large part is impractical)
Heat-affected zone:(region in which themicrostructure has beenchanged).
Fig. 11.10, Callister & Rethwisch 9e.[From Iron Castings Handbook, C.F. Walton and T.J. Opar (Ed.), Iron Castings Society,Des Plaines, IL,1981.]
piece 1 piece 2
fused base metal
filler metal (melted)base metal (melted)
unaffectedunaffectedheat-affected zone
FORMING
33
Chapter 11 -
Heat treating following prior processing affects final properties.
Effect of prior processing can be canceled out.
Thermal processing to soften (e.g. full anneal) or strengthen material (e.g. precipitation strengthening).
Thermal Processing of Metals
34
Chapter 11 -
Annealing: Heat to Tanneal, then cool slowly.
Based on discussion in Section 11.7, Callister & Rethwisch 9e.
Thermal Processing of Metals
Types of Annealing
Stress Relief: Reducestresses resulting from:
- plastic deformation - nonuniform cooling - phase transform.
Normalize (steels): Deformsteel with large grains. Then heattreat to allow recrystallization and formation of smaller grains.
Full Anneal (steels): Make soft steels for good forming. Heat to get , then furnace-coolto obtain coarse pearlite.
Spheroidize (steels): Make very soft steels for good machining. Heat just
below Teutectoid & hold for15-25 h.
35
Chapter 11 -
a) Full Annealingb) Quenching
Heat Treatment Temperature-Time Paths
c)
c) Tempering (Tempered Martensite)
P
B
A
A
a)b)
Fig. 10.25, Callister & Rethwisch 9e. [Adapted from H. Boyer (Editor), Atlas of Isothermal Transformation and Cooling Transformation Diagrams, 1977. Reproduced by permission of ASM International, Materials Park, OH.]
36
Chapter 11 -
Hardenability -- Steels Hardenability measure of the ability to form martensite Jominy end quench test used to measure hardenability.
Fig. 11.12, Callister & Rethwisch 9e. (Adapted from A.G. Guy, Essentials of Materials Science, McGraw-Hill Book Company, New York, 1978.)
24C water
specimen (heated to phase field)
flat ground
Rockwell Chardness tests
https://www.youtube.com/watch?v=nEV6RqDr9CA
37
Chapter 11 -
Hardenability -- Steels Hardenability measure of the ability to form martensite Jominy end quench test used to measure hardenability.
Plot hardness versus distance from the quenched end.
Fig. 11.12, Callister & Rethwisch 9e. (Adapted from A.G. Guy, Essentials of Materials Science, McGraw-Hill Book Company, New York, 1978.)
Fig. 11.13, Callister & Rethwisch 9e.
24C water
specimen (heated to phase field)
flat ground
Rockwell Chardness tests
Har
dnes
s, H
RC
Distance from quenched end38
Chapter 11 -
The cooling rate decreases with distance from quenched end.
Fig. 11.14, Callister & Rethwisch 9e. [Adapted from H. Boyer (Ed.), Atlas of Isothermal Transformation and Cooling Transformation Diagrams, 1977. Reproduced by permission of ASM International, Materials Park, OH.]
Reason Why Hardness Changes with Distance
distance from quenched end (in)Har
dnes
s, H
RC
20
40
60
0 1 2 3
600
400
200A M
0.1 1 10 100 1000
T(C)
M(start)
Time (s)
0
0%100%
M(finish)
39
Chapter 11 -
Hardenability vs Alloy Composition Hardenability curves for
five alloys each with, C = 0.4 wt% C
"Alloy Steels"(4140, 4340, 5140, 8640)-- contain Ni, Cr, Mo
(0.2 to 2 wt%)-- these elements shift
the "nose" to longer times (from A to B)
-- martensite is easierto form
Fig. 11.15, Callister & Rethwisch 9e. (Adapted from figure furnished courtesy Republic Steel Corporation.)
Cooling rate (C/s)
Har
dnes
s, H
RC
20
40
60
100 20 30 40 50Distance from quenched end (mm)
210100 3
41408640
5140
50
80
100
%M4340
T(C)
10-1 10 103 1050
200
400
600
800
Time (s)
M(start)M(90%)
BA
TE
40
PresenterPresentation NotesMo- Molybdenum
Chapter 11 -
Internal wing structure on Boeing 767
Aluminum is strengthened with precipitates formedby alloying.
Adapted from Fig. 11.26, Callister & Rethwisch 8e. (Fig. 11.26 is courtesy of G.H. Narayanan and A.G. Miller, Boeing Commercial Airplane Company.)
1.5m
Precipitation Strengthening
Adapted from chapter-opening photograph, Chapter 11, Callister & Rethwisch 3e. (courtesy of G.H. Narayanan and A.G. Miller, Boeing Commercial Airplane Company.)
Precipitates are developed by heat treating.42
Chapter 11 -
Particles impede dislocation motion. Ex: Al-Cu system Procedure:
0 10 20 30 40 50wt% Cu
L+L
+
+L
300
400
500
600
700
(Al)
T(C)
composition range available for precipitation hardening
CuAl2
A
Fig. 11.25, Callister & Rethwisch 9e. (Adapted from J.L. Murray, International Metals Review 30, p.5, 1985. Reprinted by permission of ASM International.)
Precipitation Hardening
Adapted from Fig. 11.23, Callister & Rethwisch 9e.
-- Pt B: quench to room temp.(retain solid solution)
-- Pt C: reheat to nucleatesmall particles within phase.
Other alloys that precipitationharden: Cu-Be Cu-Sn Mg-Al
Temp.
Time
-- Pt A: solution heat treat(get solid solution)
Pt A (soln heat treat)
B
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Pt B
C
Pt C (precipitate )
43
PresenterPresentation NotesBe- Beryllium
Chapter 11 -
2014 Al Alloy:
Maxima on TS curves. Increasing T accelerates
process.
Fig. 11.28, Callister & Rethwisch 9e. [Adapted from Metals Handbook: Properties and Selection: Nonferrous Alloys and Pure Metals, Vol. 2, 9th ed., H. Baker (Managing Ed.), 1979. Reproduced by permission of ASM International, Materials Park, OH.]
Influence of Precipitation Heat Treatment on TS, %EL
precipitation heat treat time
tens
ile s
treng
th (M
Pa)
200
300
400
100 1min 1h 1day 1mo 1yr
204C149C
Minima on %EL curves.
%E
L10
20
30
0 1min 1h 1day 1mo 1yr
204C 149C
precipitation heat treat time
44
Chapter 11 -
Ferrous alloys: steels and cast irons Non-ferrous alloys:
-- Cu, Al, Ti, and Mg alloys; refractory alloys; and noble metals. Metal fabrication techniques:
-- forming, casting, miscellaneous. Hardenability of metals
-- measure of ability of a steel to be heat treated.-- increases with alloy content.
Precipitation hardening--hardening, strengthening due to formation of
precipitate particles.--Al, Mg alloys precipitation hardenable.
Summary
45
Chapter 12 -
Chapter 12: Structures & Properties of Ceramics
ISSUES TO ADDRESS... How do the crystal structures of ceramic materials
differ from those for metals? How do point defects in ceramics differ from those
defects found in metals? How are impurities accommodated in the ceramic lattice?
How are the mechanical properties of ceramics measured, and how do they differ from those for metals?
In what ways are ceramic phase diagrams different from phase diagrams for metals?
1
Chapter 12 -
Bonding:-- Can be ionic and/or covalent in character.-- % ionic character increases with difference in
electronegativity of atoms. Degree of ionic character may be large or small:
Atomic Bonding in Ceramics
SiC: smallCaF2: large
2
Chapter 12 -
Factors that Determine Crystal Structure1. Relative sizes of ions Formation of stable structures:
--maximize the # of oppositely charged ion neighbors.
Adapted from Fig. 12.1, Callister & Rethwisch 9e.
- -
- -+
unstable
- -
- -+
stable
- -
- -+
stable2. Maintenance of
Charge Neutrality :--Net charge in ceramic
should be zero.--Reflected in chemical
formula:
CaF2: Ca2+
cationF-
F-
anions+
AmXpm, p values to achieve charge neutrality 3
PresenterPresentation NotesF: fluorineCa: Calcium
Chapter 12 -
Coordination Number increases with
Coordination Number and Ionic Radii
Adapted from Table 12.2, Callister & Rethwisch 9e.
2
rcationranion
Coord. Number
< 0.155
0.155 - 0.225
0.225 - 0.414
0.414 - 0.732
0.732 - 1.0
3
4
6
8
linear
triangular
tetrahedral
octahedral
cubic
Adapted from Fig. 12.2, Callister & Rethwisch 9e.
Adapted from Fig. 12.3, Callister & Rethwisch 9e.
Adapted from Fig. 12.4, Callister & Rethwisch 9e.
ZnS (zinc blende)
NaCl(sodium chloride)
CsCl(cesium chloride)
rcationranion
To form a stable structure, how many anions cansurround around a cation?
4
PresenterPresentation NotesZnS: Zinc sulphideCoordination number: number of anion near neighbors for a cationCl: chlorine
Chapter 12 -
Computation of Minimum Cation-Anion Radius Ratio
Determine minimum rcation/ranion for an octahedral site (C.N. = 6)
a = 2ranion
5
Chapter 12 -
On the basis of ionic radii, what crystal structurewould you predict for FeO?
Answer:
550014000770
anion
cation
...
rr
=
=
based on this ratio,-- coord # = 6 because
0.414 < 0.550 < 0.732
-- crystal structure is NaClData from Table 12.3, Callister & Rethwisch 8e.
Example Problem: Predicting the Crystal Structure of FeO
Ionic radius (nm)0.0530.0770.0690.100
0.1400.1810.133
Cation
Anion
Al3+
Fe2+
Fe3+
Ca2+
O2-
Cl-
F-6
Chapter 12 -
Rock Salt StructureSame concepts can be applied to ionic solids in general. Example: NaCl (rock salt) structure
rNa = 0.102 nm
rNa/rCl = 0.564
cations (Na+) prefer octahedral sites
Adapted from Fig. 12.2, Callister & Rethwisch 8e.
rCl = 0.181 nm
7
Chapter 12 -
MgO and FeO
O2- rO = 0.140 nm
Mg2+ rMg = 0.072 nm
rMg/rO = 0.514
cations prefer octahedral sites
So each Mg2+ (or Fe2+) has 6 neighbor oxygen atoms
Adapted from Fig. 12.2, Callister & Rethwisch 9e.
MgO and FeO also have the NaCl structure
8
Chapter 12 -
AX Crystal Structures
Fig. 12.3, Callister & Rethwisch 9e.
Cesium Chloride structure:
Since 0.732 < 0.939 < 1.0, cubic sites preferred
So each Cs+ has 8 neighbor Cl-
AXType Crystal Structures include NaCl, CsCl, and zinc blende
9
Chapter 12 -
ABX3 Crystal Structures
Adapted from Fig. 12.6, Callister & Rethwisch 8e.
Perovskite structure
Ex: complex oxide BaTiO3
10
Chapter 12 -
Silicate CeramicsMost common elements on earth are Si & O
SiO2 (silica) polymorphic forms are quartz, crystobalite, & tridymite
The strong Si-O bonds lead to a high melting temperature (1710C) for this material
Si4+
O2-
Figs. 12.9 & 12.10, Callister & Rethwisch 9e crystobalite
11
PresenterPresentation NotesCrystobalite: Tridymite: Silicate:
Chapter 12 -
Polymorphic Forms of CarbonDiamond tetrahedral bonding of
carbon hardest material known very high thermal
conductivity small crystals used to
grind/cut other materials diamond thin films
hard surface coatings used for cutting tools, medical devices, etc. Fig. 12.16, Callister &
Rethwisch 9e.
12
Chapter 12 -
Polymorphic Forms of Carbon (cont)Graphite layered structure parallel hexagonal arrays of
carbon atoms
weak forces between layers planes slide easily over one another -- good
lubricant
Fig. 12.17, Callister & Rethwisch 9e.
13
Chapter 12 -
Polymorphic Forms of Carbon (cont)Fullerenes and Nanotubes
Fullerenes spherical cluster of 60 carbon atoms, C60 Like a soccer ball
Carbon nanotubes sheet of graphite rolled into a tube Ends capped with fullerene hemispheres
Adapted from Figs. 12.18 & 12.19, Callister & Rethwisch 8e.
14
Chapter 12 -
Factors that Determine Crystal Structure1. Relative sizes of ions Formation of stable structures:
--maximize the # of oppositely charged ion neighbors.
Adapted from Fig. 12.1, Callister & Rethwisch 9e.
- -
- -+
unstable
- -
- -+
stable
- -
- -+
stable2. Maintenance of
Charge Neutrality :--Net charge in ceramic
should be zero.CaF2: Ca
2+cation
F-
F-
anions+
AmXpm, p values to achieve charge neutrality
rcationranion
determinescrystal structure
15
PresenterPresentation NotesF: fluorineCa: Calcium
Chapter 12 -
Vacancies-- vacancies exist in ceramics for both cations and anions
Interstitials-- interstitials exist for cations-- interstitials are not normally observed for anions because anions
are large relative to the interstitial sites
Fig. 12.18, Callister & Rethwisch 9e.(From W.G. Moffatt, G.W. Pearsall, and J. Wulff, The Structure and Properties of Materials, Vol. 1, Structure, p.78. Copyright 1964 by John Wiley & Sons, New York. Reprinted by permission of John Wiley and Sons, Inc.)
Point Defects in Ceramics (i)
Cation Interstitial
Cation Vacancy
Anion Vacancy 16
PresenterPresentation NotesCation:
Chapter 12 -
Frenkel Defect-- a cation vacancy-cation interstitial pair.
Shottky Defect-- a paired set of cation and anion vacancies.
Equilibrium concentration of defects
Point Defects in Ceramics (ii)
Shottky Defect:
Frenkel Defect
Fig. 12.19, Callister & Rethwisch 9e.(From W.G. Moffatt, G.W. Pearsall, and J. Wulff, The Structure and Properties of Materials, Vol. 1, Structure, p.78. Copyright 1964 by John Wiley & Sons, New York. Reprinted by permission of John Wiley and Sons, Inc.)
17
Chapter 12 -
Ceramic Phase DiagramsMgO-Al2O3 diagram:
Fig. 12.23, Callister & Rethwisch 9e. [Adapted from B. Hallstedt,Thermodynamic Assessment of the System MgOAl2O3, J. Am. Ceram. Soc., 75[6], 1502 (1992). Reprinted by permission of the American Ceramic Society.]
18
Chapter 12 -
Mechanical PropertiesCeramic materials are more brittle than metals.
Why is this so? Consider mechanism of deformation
In crystalline, by dislocation motion In highly ionic solids, dislocation motion is difficult
few slip systems resistance to motion of ions of like charge (e.g., anions)
past one another bend test to measure room-T flexural strength.
FL/2 L/2
= midpoint deflection
cross section
R
b
d
rect. circ.
location of max tension19
Chapter 12 -
SUMMARY Interatomic bonding in ceramics is ionic and/or covalent. Ceramic crystal structures are based on:
-- maintaining charge neutrality-- cation-anion radii ratios.
Imperfections-- Atomic point: vacancy, interstitial (cation), Frenkel, Schottky-- Impurities: substitutional, interstitial-- Maintenance of charge neutrality
Room-temperature mechanical behavior flexural tests
20
Chapter 13 - 1
Chapter 13: Applications and
Processing of Ceramics
ISSUES TO ADDRESS...
How do we classify ceramics?
What are some applications of ceramics?
How is processing of ceramics different than for metals?
Chapter 13 - 2
Glasses Clay
products
Refractories Abrasives Cements Advanced
ceramics
-optical
-composite
reinforce
-containers/
household
-whiteware
-structural
-bricks for
high T
(furnaces)
-sandpaper
-cutting
-polishing
-composites
-structural
-engine
rotors
valves
bearings-sensors
Adapted from Fig. 13.1 and discussion in
Section 13.2-8, Callister & Rethwisch 8e.
Classification of Ceramics
Ceramic Materials
Chapter 13 - 3
tensile force
Ao
Addie
die
Die blanks:-- Need wear resistant properties!
Die surface:-- 4 mm polycrystalline diamond
particles that are sintered onto a
cemented tungsten carbide
substrate.
-- polycrystalline diamond gives uniform
hardness in all directions to reduce
wear.
Adapted from Fig. 11.8(d),
Callister & Rethwisch 8e.
Courtesy Martin Deakins, GE
Superabrasives, Worthington,
OH. Used with permission.
Ceramics Application: Die Blanks
Chapter 13 - 4
Tools:-- for grinding glass, tungsten,
carbide, ceramics
-- for cutting Si wafers
-- for oil drilling
bladesoil drill bits
Single crystal
diamonds
polycrystalline
diamonds in a resin
matrix.
Photos courtesy Martin Deakins,
GE Superabrasives, Worthington,
OH. Used with permission.
Ceramics Application:
Cutting Tools
Materials:-- manufactured single crystal
or polycrystalline diamonds
in a metal or resin matrix.
-- polycrystalline diamonds
resharpen by microfracturing
along cleavage planes.
Chapter 13 - 5
Materials to be used at high temperatures (e.g., in high temperature furnaces).
Consider the Silica (SiO2) - Alumina (Al2O3) system. Silica refractories - silica rich - small additions of alumina
depress melting temperature (phase diagram):
Fig. 12.27, Callister &
Rethwisch 8e. (Fig. 12.27
adapted from F.J. Klug and
R.H. Doremus, J. Am. Cer.
Soc. 70(10), p. 758, 1987.)
Refractories
Composition (wt% alumina)
T(C)
1400
1600
1800
2000
2200
20 40 60 80 1000
alumina+
mullite
mullite + L
mulliteLiquid
(L)
mullite+ crystobalite
crystobalite + L
alumina + L
3Al2O3-2SiO2
Chapter 13 - 6
Advanced Ceramics:
Materials for Automobile Engines
Advantages:
Operate at high temperatures high efficiencies
Low frictional losses
Operate without a cooling system
Lower weights than current engines
Disadvantages:
Ceramic materials are brittle
Difficult to remove internal voids (that weaken
structures)
Ceramic parts are difficult to form and machine
Potential candidate materials: Si3N4, SiC, & ZrO2 Possible engine parts: engine block & piston coatings
Chapter 13 - 7
Advanced Ceramics:
Materials for Ceramic Armor
Components:-- Outer facing plates
-- Backing sheet
Properties/Materials:-- Facing plates -- hard and brittle
fracture high-velocity projectile Al2O3, B4C, SiC, TiB2
-- Backing sheets -- soft and ductile
deform and absorb remaining energy aluminum, synthetic fiber laminates
Chapter 13 - 8
Blowing of Glass Bottles:
GLASS
FORMING
Adapted from Fig. 13.8, Callister & Rethwisch 8e. (Fig. 13.8 is adapted from C.J.
Phillips, Glass: The Miracle Maker, Pittman Publishing Ltd., London.)
Ceramic Fabrication Methods (i)
Gob
Parison mold
Pressing operation
Suspended parison
Finishing mold
Compressed air
Fiber drawing:
wind up
PARTICULATE
FORMING
CEMENTATION
-- glass formed by application of
pressure
-- mold is steel with graphite
lining
Pressing: plates, cheap glasses
Chapter 13 - 9
Sheet Glass Forming
Sheet forming continuous casting
sheets are formed by floating the molten glass on a pool of molten tin
Adapted from Fig. 13.9,
Callister & Rethwisch 8e.
Chapter 13 -10
Quartz is crystallineSiO2:
Basic Unit: Glass is noncrystalline (amorphous) Fused silica is SiO2 to which no
impurities have been added
Other common glasses contain impurity ions such as Na+, Ca2+,
Al3+, and B3+
(soda glass)
Adapted from Fig. 12.11,
Callister & Rethwisch 8e.
Glass Structure
Si04 tetrahedron4-
Si4+
O2-
Si4+
Na+
O2-
Chapter 13 - 11
Specific volume (1/r) vs Temperature (T):
Glasses: -- do not crystallize
-- change in slope in spec. vol. curve at
glass transition temperature, Tg-- transparent - no grain boundaries to
scatter light
Crystalline materials: -- crystallize at melting temp, Tm-- have abrupt change in spec.
vol. at Tm
Adapted from Fig. 13.6,
Callister & Rethwisch 8e.
Glass Properties
T
Specific volume
Supercooled Liquid
solid
Tm
Liquid(disordered)
Crystalline (i.e., ordered)
Tg
Glass
(amorphous solid)
Chapter 13 -
Production Processes
12
https://www.youtube.com/watch?v=yvqLtTUlZcA
Glass bottles:
https://www.youtube.com/watch?v=dw7623hu7wM
Glass windows:
Chapter 13 -14
Mill (grind) and screen constituents: desired particle size
Extrude this mass (e.g., into a brick)
Dry and fire the formed piece
ram billet
container
containerforce
die holder
die
Ao
AdextrusionAdapted from
Fig. 12.8(c),
Callister &
Rethwisch 8e.
Ceramic Fabrication Methods (iia)
GLASS
FORMING
PARTICULATE
FORMING
CEMENTATION
Hydroplastic forming:
Chapter 13 -15
Mill (grind) and screen constituents: desired particle size
Slip casting operation
Dry and fire the cast piece
Ceramic Fabrication Methods (iia)
solid component
Adapted from Fig.
13.12, Callister &
Rethwisch 8e. (Fig.
13.12 is from W.D.
Kingery, Introduction
to Ceramics, John
Wiley and Sons,
Inc., 1960.)
hollow component
pour slip
into mold
drain
moldgreen ceramic
pour slip into mold
absorb water into mold
green ceramic
GLASS
FORMING
PARTICULATE
FORMING
CEMENTATION
Slip casting:
Mix with water and other constituents to form slip
Chapter 13 -16
Typical Porcelain Composition
(50%) 1. Clay
(25%) 2. Filler e.g. quartz (finely ground)
(25%) 3. Fluxing agent (Feldspar)
-- aluminosilicates plus K+, Na+, Ca+
-- upon firing - forms low-melting-temp. glass
https://www.youtube.com/watch?v=9lD999ZjD7E
Porcelain
Porcelain Production:
Chapter 13 -17
Drying: as water is removed - interparticle spacings decrease shrinkage .
Adapted from Fig.
13.13, Callister &
Rethwisch 8e. (Fig.
13.13 is from W.D.
Kingery, Introduction
to Ceramics, John
Wiley and Sons,
Inc., 1960.)
Drying and Firing
Drying too fast causes sample to warp or crack due to non-uniform shrinkage
wet body partially dry completely dry
Firing:-- heat treatment between
900-1400C
-- vitrification: liquid glass forms
from clay and flux flows between SiO2 particles. (Flux
lowers melting temperature). Adapted from Fig. 13.14, Callister & Rethwisch 8e. (Fig. 13.14 is courtesy H.G. Brinkies, Swinburne
University of Technology, Hawthorn Campus,
Hawthorn, Victoria, Australia.)
Si02 particle
(quartz)
glass formed around the particle
mic
rog
rap
h o
f p
orc
ela
in
70mm
Chapter 13 -18
Powder Pressing: used for both clay and non-clay compositions.
Powder (plus binder) compacted by pressure in a mold-- Uniaxial compression - compacted in single direction
-- Isostatic (hydrostatic) compression - pressure applied by
fluid - powder in rubber envelope
-- Hot pressing - pressure + heat
Ceramic Fabrication Methods (iib)
GLASS
FORMING
PARTICULATE
FORMING
CEMENTATION
Chapter 13 -19
Sintering
Adapted from Fig. 13.16,
Callister & Rethwisch 8e.
Aluminum oxide powder:-- sintered at 1700C
for 6 minutes.Adapted from Fig. 13.17, Callister
& Rethwisch 8e. (Fig. 13.17 is from
W.D. Kingery, H.K. Bowen, and
D.R. Uhlmann, Introduction to
Ceramics, 2nd ed., John Wiley and
Sons, Inc., 1976, p. 483.)
15mm
Sintering occurs during firing of a piece that has
been powder pressed
-- powder particles coalesce and reduction of pore size
Chapter 13 -20
Tape Casting Thin sheets of green ceramic cast as flexible tape
Used for integrated circuits and capacitors
Slip = suspended ceramic particles + organic liquid (contains binders, plasticizers)
Fig. 13.18, Callister &
Rethwisch 8e.
Chapter 13 -21
Hardening of a paste paste formed by mixing cement material with water
Formation of rigid structures having varied and complex
shapes
Hardening process hydration (complex chemical reactions involving water and cement particles)
Ceramic Fabrication Methods (iii)
GLASS
FORMING
PARTICULATE
FORMING
CEMENTATION
Portland cement production of:-- mix clay and lime-bearing minerals
-- calcine (heat to 1400C)
-- grind into fine powder
https://www.youtube.com/watch?v=m8U76Bm8kDY
Chapter 13 -22
Categories of ceramics: -- glasses -- clay products
-- refractories -- cements
-- advanced ceramics
Ceramic Fabrication techniques:-- glass forming (pressing, blowing, fiber drawing).
-- particulate forming (hydroplastic forming, slip casting,
powder pressing, tape casting)
-- cementation
Heat treating procedures-- glassesannealing-- particulate formed piecesdrying, firing (sintering)
Summary
Chapter 14 -
11.2, 11.7 (composition only), 11.19, 11.24, 11.D14Due: Wednesday April 8th, 2015
Homework IV Assignment
Homework V Assignment
Due: Wednesday April 15th, 2015
Exam III: Wednesday April 22nd, 2015
12.4, 12.5, 13.8, 13.21
1
Chapter 14 -
Coordination Number increases with
Coordination Number and Ionic Radii
Adapted from Table 12.2, Callister & Rethwisch 9e.
2
rcationranion
Coord. Number
< 0.155
0.155 - 0.225
0.225 - 0.414
0.414 - 0.732
0.732 - 1.0
3
4
6
8
linear
triangular
tetrahedral
octahedral
cubic
Adapted from Fig. 12.2, Callister & Rethwisch 9e.
Adapted from Fig. 12.3, Callister & Rethwisch 9e.
Adapted from Fig. 12.4, Callister & Rethwisch 9e.
ZnS (zinc blende)
NaCl(sodium chloride)
CsCl(cesium chloride)
rcationranion
To form a stable structure, how many anions cansurround around a cation?
2
Chapter 14 -
ISSUES TO ADDRESS... What are the general structural and chemical
characteristics of polymer molecules? What are some of the common polymeric
materials, and how do they differ chemically?
How is the structure of polymers different than that in metals and ceramics ?
Chapter 14:Polymer Structures
3
Chapter 14 -
What is a Polymer?
Poly mermany repeat unit
Adapted from Fig. 14.2, Callister & Rethwisch 9e.
C C C C C CHHHHHH
HHHHHH
Polyethylene (PE)ClCl Cl
C C C C C CHHH
HHHHHH
Poly(vinyl chloride) (PVC)HH
HHH H
Polypropylene (PP)
C C C C C CCH3
HH
CH3CH3H
repeatunit
repeatunit
repeatunit
4
Chapter 14 -
Natural Polymers Originally natural polymers were used
Wood Rubber Cotton Wool Leather Silk
Oldest known uses Rubber balls used by Incas Biblical reference to pitch(a natural polymer)
5
Chapter 14 -
Polymer CompositionMost polymers are hydrocarbons
i.e., made up of H and C Saturated hydrocarbons
Each carbon singly bonded to four other atoms Example:
Ethane, C2H6
C C
H
H H H
HH
6
Chapter 14 - 7
Chapter 14 -
Unsaturated Hydrocarbons Double & triple bonds somewhat unstable
can form new bonds Double bond found in ethylene - C2H4
Triple bond found in acetylene - C2H2
C CH
H
H
H
C C HH
8
Chapter 14 -
Chemistry and Structure of Polyethylene
Adapted from Fig. 14.1, Callister & Rethwisch 9e.
Note: polyethylene is a long-chain hydrocarbon- paraffin wax for candles is short polyethylene
9
Chapter 14 -
Isomerism Isomerism
two compounds with same chemical formula can have quite different structures
for example: C8H18 normal-octane
2,4-dimethylhexane
C C C C C C C CH
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H H3C CH2 CH2 CH2 CH2 CH2 CH2 CH3=
H3C CH
CH3CH2 CH
CH2
CH3
CH3
H3C CH2 CH3( )6
10
Chapter 14 -
Bulk or Commodity Polymers
12
Chapter 14 -
Adapted from Fig. 14.7, Callister & Rethwisch 9e.
Molecular Structures for Polymers
Branched Cross-Linked NetworkLinear
secondarybonding
15
Chapter 14 -
Polymers Molecular ShapeMolecular Shape chain bending and twisting
are possible by rotation of carbon atoms around their chain bonds note: not necessary to break chain bonds
to alter molecular shapeAdapted from Fig. 14.5, Callister & Rethwisch 9e.
16
Chapter 14 -
Chain End-to-End Distance, r
Fig. 14.6, Callister & Rethwisch 9e.
17
Chapter 14 -
Polymer Crystallinity Crystalline regions
thin platelets with chain folds at faces Chain folded structure
Fig. 14.12, Callister & Rethwisch 9e.
10 nm
18
Chapter 14 -
Crystallinity in Polymers Ordered atomic
arrangements involving molecular chains
Crystal structures in terms of unit cells
Example shown polyethylene unit cell
Fig. 14.10, Callister & Rethwisch 9e.
19
Chapter 14 -
Polymer Crystallinity (cont.)Polymers rarely 100% crystalline Difficult for all regions of all chains to
become aligned
Degree of crystallinity expressed as % crystallinity.-- Some physical properties
depend on % crystallinity.-- Heat treating causes
crystalline regions to grow and % crystallinity to increase.
Fig. 14.11, Callister 6e. (From H.W. Hayden, W.G. Moffatt, and J. Wulff, The Structure and Properties of Materials, Vol. III, Mechanical Behavior, John Wiley and Sons, Inc., 1965.)
crystalline region
amorphousregion
20
Chapter 14 -
Semicrystalline Polymers
Spherulite surface
Fig. 14.13, Callister & Rethwisch 9e.
Some semicrystalline polymers form spherulite structures
Alternating chain-folded crystallites and amorphous regions
Spherulite structure for relatively rapid growth rates
21
Chapter 14 -
MOLECULAR WEIGHT Molecular weight, M: Mass of a mole of chains.
Low M
high M
Not all chains in a polymer are of the same length i.e., there is a distribution of molecular weights
22
Chapter 14 -
MOLECULAR WEIGHT DISTRIBUTION
Fig. 14.4, Callister & Rethwisch 9e.
= numerical average
23
Chapter 14 -
Degree of Polymerization, DPDP = average number of repeat units per chain
C C C C C C C CH
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
C C C C
H
H
H
H
H
H
H
H
H( ) DP = 6
mol. wt of repeat unit iChain fraction28
Chapter 14 -
Copolymerstwo or more monomers
polymerized together random A and B randomly
positioned along chain alternating A and B
alternate in polymer chain block large blocks of A
units alternate with large blocks of B units
graft chains of B units grafted onto A backbone
A B
random
block
graft
Fig. 14.9, Callister & Rethwisch 9e.
alternating
29
Chapter 15 -
Chapter 15: Characteristics, Applications &
Processing of Polymers
ISSUES TO ADDRESS...
What are the tensile properties of polymers and how are they affected by basic microstructural features?
Hardening, anisotropy, and annealing in polymers.
How does the elevated temperature mechanicalresponse of polymers compare to ceramics and metals?
What are the primary polymer processing methods?
1
Chapter 15 -
Mechanical Properties of Polymers Stress-Strain Behavior
Fracture strengths of polymers ~ 10% of those for metals Deformation strains for polymers > 1000%
for most metals, deformation strains < 10%
brittle polymer
plasticelastomer
elastic moduli less than for metals Adapted from Fig. 15.1,
Callister & Rethwisch 9e.
2
Chapter 15 -
Mechanical Properties of Polymers Stress-Strain Behavior
www.packaging-gateway.com3
Chapter 15 -
Mechanisms of DeformationBrittle Crosslinked and Network Polymers
brittle failure
plastic failure
e
x
x
aligned, crosslinkedpolymer Stress-strain curves adapted from Fig. 15.1,
Callister & Rethwisch 9e.
InitialNear
Failure
network polymer
(MPa)
4
Chapter 15 -
Mechanisms of Deformation Semicrystalline (Plastic) Polymers
brittle failure
plastic failure
(MPa)
x
x
crystallineblock segments
separate
fibrillar structure
near failure
crystallineregions align
onset of necking
undeformedstructure amorphous
regionselongate
unload/reload
Stress-strain curves adapted from Fig. 15.1, Callister & Rethwisch 9e. Inset figures along plastic response curve adapted from Figs. 15.12 & 15.13, Callister & Rethwisch 9e. (From SCHULTZ, POLYMER MATERIALS SCIENCE, 1st Edition, 1974. Reprinted by permission of Pearson Education, Inc., Upper Saddle River, NJ.)1974, pp 500-501.)
e
5
Chapter 15 -
Predeformation by Drawing Drawing(ex: monofilament fishline)
-- stretches the polymer prior to use-- aligns chains in the stretching direction
Results of drawing:-- increases the elastic modulus (E) in the
stretching direction-- increases the tensile strength (TS) in the
stretching direction-- decreases ductility (%EL)
Annealing after drawing...-- decreases chain alignment-- reverses effects of drawing (reduces E and
TS, enhances %EL) Contrast to effects of cold working in metals!
Adapted from Fig. 15.13, Callister & Rethwisch 9e.(From Schultz, Polymer Materials Science, 1st Edition, 1974. Reprinted by permission of Pearson Education, Inc., Upper Saddle River, NJ.)1974, pp 500-501.)
6
Chapter 15 -
Compare elastic behavior of elastomers with the:-- brittle behavior (of aligned, crosslinked & network polymers), and-- plastic behavior (of semicrystalline polymers)
(as shown on previous slides)
Stress-strain curves adapted from Fig. 15.1, Callister & Rethwisch 9e.Inset figures along elastomer curve (green) adapted from Fig. 15.15, Callister & Rethwisch 9e. (Fig. 15.15 adapted from Z. D. Jastrzebski, The Nature and Properties of Engineering Materials, 3rd edition. Copyright 1987 by John Wiley & Sons, New York. Reprinted by permission of John Wiley & Sons, Inc.)
Mechanisms of DeformationElastomers
initial: amorphous chains are kinked, cross-linked.
x
final: chainsare straighter,
stillcross-linked
elastomer
deformation is reversible (elastic)!
brittle failure
plastic failurex
x(MPa)
e
7
Chapter 15 -
Thermoplastics:-- little crosslinking-- ductile-- soften w/heating-- polyethylene, polypropylene
polycarbonate, polystyrene
Thermoplastics vs. Thermosets
8
Chapter 15 -
Thermosets:-- significant crosslinking
(10 to 50% of repeat units)-- hard and brittle-- do NOT soften w/heating-- vulcanized rubber, epoxies,
polyester resin, phenolic resin
Thermoplastics vs. Thermosets
9
Chapter 15 -
Decreasing T...-- increases E-- increases TS-- decreases %EL
Increasingstrain rate...
-- same effectsas decreasing T.
Adapted from Fig. 15.3, Callister & Rethwisch 9e. (Reprinted with permission from T. S. Carswell and H. K. Nason, Effect of Environmental Conditions on the Mechanical Properties of Organic Plastics, in Symposium on Plastics. Copyright ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428.)
Influence of T and Strain Rate on Thermoplastics
20
40
60
80
00 0.1 0.2 0.3
4C
20C
40C
60C to 1.3
Plots forsemicrystalline PMMA (Plexiglas)
(MPa)
e
10
Chapter 15 -
Melting & Glass Transition Temps.What factors affect Tm and Tg?
Both Tm and Tg increase with increasing chain stiffness
Chain stiffness increased by presence of1. Bulky sidegroups2. Chain double bonds
Adapted from Fig. 15.18, Callister & Rethwisch 9e.
Representative Tg values (C):PE (low density)PE (high density)PVCPSPC
- 110- 90+ 87+100+150
Selected values from Table 15.2, Callister & Rethwisch 9e.
11
Chapter 15 -
Stress relaxation test:-- strain in tension to e
and hold.-- observe decrease in
stress with time.
Relaxation modulus:
Time-Dependent Deformation
time
straintensile test
eo(t)
There is a large decrease in Erfor T > Tg. (amorphous
polystyrene)Fig. 15.7, Callister & Rethwisch 9e. (From A. V. Tobolsky, Properties and Structures of Polymers. Copyright 1960 by John Wiley & Sons, New York. Reprinted by permission of John Wiley & Sons, Inc.)
103
101
10-1
10-3
105
60 100 140 180
rigid solid (small relax)
transition region
T(C)Tg
Er (10 s)in MPa
viscous liquid (large relax)
12
Chapter 15 -
Polymer Formation There are two types of polymerization
Addition (or chain) polymerization
Condensation (step) polymerization (beyond scope)
13
Chapter 15 -
Addition (Chain) Polymerization
InitiationR: initiator or catalyst
Propagation
Termination
14
Chapter 15 -
Polymer AdditivesImprove mechanical properties, processability,
durability, etc. Fillers
Added to improve tensile strength & abrasion resistance, toughness & decrease cost
ex: carbon black, glass, limestone, talc, etc.
Plasticizers small molecules that take place between polymer chains-reduce secondary bonding Presence of plasticizer transforms brittle polymer to a
ductile one Commonly added to PVC - otherwise it is brittle
15
Chapter 15 -
Polymer Additives (cont.) Stabilizers
UV protectants Lubricants
Added to allow easier processing polymer slides through dies easier
Colorants Dyes and pigments
Flame Retardants Substances containing chlorine, fluorine, and boron
16
Chapter 15 -
Processing of Plastics Thermoplastic
can be reversibly cooled & reheated, i.e. recycled heat until soft, shape as desired, then cool ex: polyethylene, polypropylene, polystyrene.
Thermoset forms a molecular network (chemical reaction) degrades (doesnt melt) when heated a prepolymer molded into desired shape, then
chemical reaction occurs ex: urethane, epoxy
17
Chapter 15 -
Example: Two component epoxy glue
Thermoset
18
Chapter 15 -
Processing Plastics Compression MoldingThermoplastics and thermosets polymer and additives placed in mold cavity mold heated and pressure applied fluid polymer assumes shape of mold
Fig. 15.23, Callister & Rethwisch 9e. (From F. W. Billmeyer, Jr., Textbook of Polymer Science, 3rd edition. Copyright 1984 by John Wiley & Sons, New York. Reprinted by permission of John Wiley & Sons, Inc.)
19
Chapter 15 -
Processing Plastics Injection Molding
Fig. 15.24, Callister & Rethwisch 9e. (From F. W. Billmeyer, Jr., Textbook of Polymer Science, 3rd edition. Copyright 1984 by John Wiley & Sons, New York. Reprinted by permission of John Wiley & Sons, Inc.)
Thermoplastics and some thermosets when ram retracts, plastic pellets drop from hopper into barrel ram forces plastic into the heating chamber (around the
spreader) where the plastic melts as it moves forward molten plastic is forced under pressure (injected) into the mold
cavity where it assumes the shape of the mold
Barrelhttps://www.youtube.com/watch?v=eUthHS3MTdA
20
Chapter 15 -
Processing Plastics Extrusion
Fig. 15.25, Callister & Rethwisch 9e. (Reprinted with permission from Encyclopdia Britannica, 1997 by Encyclopdia Britannica, Inc.)
thermoplastics plastic pellets drop from hopper onto the turning screw plastic pellets melt as the turning screw pushes them
forward by the heaters molten polymer is forced under pressure through the
shaping die to form the final product
21
Chapter 15 -
Processing Plastics Blown-Film Extrusion
Fig. 15.26, Callister & Rethwisch 9e. (Reprinted with permission from Encyclopdia Britannica, 1997 by Encyclopdia Britannica, Inc.)
22
Chapter 15 -
Polymer Types FibersFibers - length/diameter >100 Primary use is in textiles. Fiber characteristics:
high tensile strengths high degrees of crystallinity Nylon:https://www.youtube.com/watch?v=yFEHKRdXb9Y
Formed by spinning extrude polymer through a spinneret (a die
containing many small orifices) the spun fibers are drawn under tension leads to highly aligned chains - fibrillar structure
23
Chapter 15 -
Polymer Types Miscellaneous Coatings thin polymer films applied to surfaces i.e.,
paints, varnishes protects from corrosion/degradation decorative improves appearance can provide electrical insulation
Adhesives bonds two solid materials (adherands)
Films produced by blown film extrusion
Foams gas bubbles incorporated into plastic
https://www.youtube.com/watch?v=xjap74m4228
24
Chapter 15 -
Advanced Polymers
Molecular weight ca. 4x106 g/mol Outstanding properties
high impact strength resistance to wear/abrasion low coefficient of friction self-lubricating surface
Important applications bullet-proof vests golf ball covers hip implants (acetabular cup)
UHMWPE
Adapted from chapter-opening photograph, Chapter 22, Callister 7e.
Ultrahigh Molecular Weight Polyethylene (UHMWPE)
25
Chapter 15 -
Advanced Polymers
styrene
butadiene
Thermoplastic Elastomers
Styrene-butadiene block copolymerhard
component domain
soft component
domainFig. 15.22, Callister & Rethwisch 9e.Fig. 15.21(a), Callister & Rethwisch 9e.
26
Chapter 15 -
Limitations of polymers:-- E, y, Tapplication are generally small.-- Deformation is often time and temperature dependent.
Thermoplastics (PE, PS, PP, PC):-- Smaller E, y, Tapplication-- Easier to form and recycle
Elastomers (rubber):-- Large reversible strains!
Thermosets (epoxies, polyesters):-- Larger E, y, Tapplication
Table 15.3 Callister & Rethwisch 9e:
Good overviewof applicationsand trade namesof polymers.
Summary
27
Chapter 15 -
Summary Polymer Processing
-- compression and injection molding, extrusion, blown film extrusion
Polymer melting and glass transition temperatures Polymer applications
-- elastomers -- fibers-- coatings -- adhesives-- films -- foams-- advanced polymeric materials
28
Chapter 16 - 1
Reminders
Homework V Assignment
Due: Wednesday April 15th, 2015
Exam III: Wednesday April 22nd, 2015Chapter 11, 12, 13, 14, 15, 16
12.4, 12.5, 13.8, 13.21
Chapter 16 - 2
ISSUES TO ADDRESS... What are the classes and types of composites?
What are the advantages of using composite materials?
How do we predict the stiffness and strength of the various types of composites?
Chapter 16: Composites
Chapter 16 - 3
Composite
Combination of two or more individual materials
Design goal: obtain a more desirable combination of properties e.g., low density and high strength
Chapter 16 - 4
Composite:-- Multiphase material
Phase types:-- Matrix - is continuous-- Dispersed - is discontinuous and
surrounded by matrix
Terminology/Classification
Adapted from Fig. 16.1(a), Callister & Rethwisch 9e.
Chapter 16 - 5
Matrix phase:-- Purposes are to:
- transfer stress to dispersed phase- protect dispersed phase from environment
-- Types: MMC, CMC, PMC
metal ceramic polymer
Terminology/Classification
Dispersed phase:-- Types: particle, fiber
Reprinted with permission fromD. Hull and T.W. Clyne, An Introduction to Composite Materials, 2nd ed., Cambridge University Press, New York, 1996, Fig. 3.6, p. 47.
woven fibers
cross section view
0.5mm
0.5mm
Chapter 16 - 6
Chapter 16 -
Chapter 16 -
Boeing 787 Dreamliner
8
http://www.reinforcedplastics.com/
http://www.boeing.com/
http://www.dailytech.com/
https://www.youtube.com/watch?v=f07HpUAuWgk
Chapter 16 - 9
Classification of Composites
Large-particle
Dispersion-strengthened
Particle-reinforced
Continuous(aligned)
Aligned Randomlyoriented
Discontinuous(short)
Fiber-reinforced
Laminates Sandwichpanels
Structural
Composites
Adapted from Fig. 16.2, Callister & Rethwisch 9e.
Chapter 16 - 10
Classification: Particle-Reinforced (i)
Examples:
Fig. 11.19, Callister & Rethwisch 9e. (Copyright 1971 by United States Steel Corporation.)
- Spheroidite steel
matrix: ferrite ()(ductile)
particles: cementite(Fe
3C)
(brittle)60m
Fig. 16.4, Callister & Rethwisch 9e. (Courtesy of Carboloy Systems Department, General Electric Company.)
- WC/Co cemented carbide
matrix: cobalt (ductile, tough)
particles: WC (brittle, hard):
600m
Fig. 16.5, Callister & Rethwisch 9e. (Courtesy of Goodyear Tire and Rubber Company.)
- Automobile tire rubber
matrix: rubber (compliant)
particles: carbon black (stiff) 0.75m
Particle-reinforced Fiber-reinforced Structural
Chapter 16 - 11
Classification: Particle-Reinforced (ii)
Concrete gravel + sand + cement + water- Why sand and gravel? Sand fills voids between gravel particles
Reinforced concrete Reinforce with steel rebar or remesh- increases strength - even if cement matrix is cracked
Particle-reinforced Fiber-reinforced Structural
http://www.rebartool.com/
Chapter 16 - 12
Elastic modulus, Ec, of composites:-- rule of mixture:
Application to other properties:-- Electrical conductivity, e: Replace Es in equation with es.-- Thermal conductivity, k: Replace Es in equation with ks.
Fig. 16.3, Callister & Rethwisch 9e. (Reprinted with permission from R. H. Krock, ASTM Proceedings, Vol. 63, 1963. Copyright ASTM International, 100 Barr Harbor Drive, West Conschohocken, PA 19428.)
Classification: Particle-Reinforced (iii)
upper limit: c m mE = V E + VpEp
Particle-reinforced Fiber-reinforced Structural
Data: Cu matrix w/tungsten particles
0 20 40 60 80 100
150200250300350
vol% tungsten
E(GPa)
(Cu) (W)
Chapter 16 - 13
Classification: Fiber-Reinforced (i)
Fibers very strong in tension Provide significant strength improvement to the
composite Ex: fiber-glass - continuous glass filaments in a
polymer matrix Glass fibers
strength and stiffness Polymer matrix
holds fibers in place protects fiber surfaces transfers load to fibers
Particle-reinforced Fiber-reinforced Structural
Chapter 16 - 14
Classification: Fiber-Reinforced (ii)
Fiber TypesParticle-reinforced Fiber-reinforced Structural
Fibers polycrystalline or amorphous generally polymers or ceramics Ex: alumina, aramid, boron, UHMWPE
Wires metals steel, molybdenum, tungsten
Chapter 16 - 15
Fiber Alignment
alignedcontinuous
aligned randomdiscontinuous
Fig. 16.8, Callister & Rethwisch 9e.
Transverse direction
Longitudinal direction
Chapter 16 - 16
Aligned Continuous fibers Examples:
From W. Funk and E. Blank, Creep deformation of Ni3Al-Mo in-situ composites", Metall. Trans. A Vol. 19(4), pp. 987-998, 1988. Used with permission.
-- Metal: (Ni3Al)-(Mo)by eutectic solidification.
Classification: Fiber-Reinforced (iii)
Particle-reinforced Fiber-reinforced Structural
matrix: (Mo) (ductile)
fibers: (Ni3Al) (brittle)
2m
-- Ceramic: Glass w/SiC fibersformed by glass slurryEglass = 76 GPa; ESiC = 400 GPa.
From F.L. Matthews and R.L. Rawlings, Composite Materials; Engineering and Science, Reprint ed., CRC Press, Boca Raton, FL, 2000. Used with permission of CRCPress, Boca Raton, FL.
Chapter 16 - 17
Discontinuous fibers, random in 2 dimensions Example: Carbon-Carbon
-- carbon fibers embedded in polymer resin matrix,
-- uses: disk brakes, gas turbine exhaust flaps, missile nose cones.
Other possibilities:-- Discontinuous, random 3D-- Discontinuous, aligned
Adapted from F.L. Matthews and R.L. Rawlings, Composite Materials; Engineering and Science, Reprint ed., CRC Press, Boca Raton, FL, 2000. (a) Fig. 4.24(a), p. 151; (b) Fig. 4.24(b) p. 151. (Courtesy I.J. Davies) Reproduced with permission of CRC Press, Boca Raton, FL.
Classification: Fiber-Reinforced (iv)
Particle-reinforced Fiber-reinforced Structural
(b)
fibers lie in plane
view onto plane
C fibers: very stiff very strong
C matrix: less stiff less strong
(a)
500 m
Chapter 16 - 18
Composite Stiffness:Longitudinal Loading
Continuous fibers - Estimate fiber-reinforced composite modulus of elasticity for continuous fibers
Longitudinal deformation
c = mVm + fVf and ec = em = ef
volume fraction isostrain
Ecl = EmVm + Ef Vf Ecl = longitudinal modulus
c = compositef = fiberm = matrix
Chapter 16 -Fig_16-9
Chapter 16 - 20
Composite Production Methods (i)
Fig. 16.13, Callister & Rethwisch 9e.
Pultrusion Continuous fibers pulled through resin tank to impregnate fibers with
thermosetting resin Impregnated fibers pass through steel die that preforms to the desired shape Preformed stock passes through a curing die that is
precision machined to impart final shape heated to initiate curing of the resin matrix
Chapter 16 - 21
Composite Production Methods (ii) Filament Winding
Continuous reinforcing fibers are accurately positioned in a predetermined pattern to form a hollow (usually cylindrical) shape
Fibers are fed through a resin bath to impregnate with thermosetting resin Impregnated fibers are continuously wound (typically automatically) onto a
mandrel After appropriate number of layers added, curing is carried out either in an
oven or at room temperature The mandrel is removed to give the final product
Fig. 16.15, Callister & Rethwisch 9e. [From N. L. Hancox, (Editor), Fibre Composite Hybrid Materials, The Macmillan Company, New York, 1981.]
Chapter 16 - 22
Laminates --- stacked and bonded fiber-reinforced sheets
- stacking sequence: e.g., 0/90Adapted from Fig. 16.16, Callister & Rethwisch 8e.
Classification: StructuralParticle-reinforced Fiber-reinforced Structural
Sandwich panels-- honeycomb core between two facing sheets
- benefits: low density, large bending stiffness
honeycombadhesive layer
face sheet
Fig. 16.18, Callister & Rethwisch 9e. (Reprinted with permission from Engineered Materials Handbook, Vol. 1, Composites,ASM International, Materials Park, OH, 1987.)
Chapter 16 - 23
Composites types are designated by:-- the matrix material (CMC, MMC, PMC)-- the reinforcement (particles, fibers, structural)
Composite property benefits:-- MMC: enhanced E, , creep performance-- CMC: enhanced toughness-- PMC: enhanced E/, y, TS/
Particulate-reinforced:-- Types: large-particle and dispersion-strengthened-- Properties are isotropic
Fiber-reinforced:-- Types: continuous (aligned)
discontinuous (aligned or random)-- Properties can be isotropic or anisotropic
Structural:-- Laminates and sandwich panels
Summary
RemindersChapter 11: Applications and Processing of Metal AlloysSlide Number 3Slide Number 4Slide Number 5Slide Number 6Slide Number 7Slide Number 8Slide Number 9Slide Number 10Classification of Metal AlloysSteelsFerrous AlloysFerrous Alloys:Advanced High Strength Steels (AHSS)Slide Number 15Slide Number 16Cast IronsFe-C True Equilibrium Diagram Types of Cast IronProduction of Cast IronsTypes of Cast Iron (cont.)Types of Cast Iron (cont.)Limitations of Ferrous AlloysClassification scheme for nonferrous alloysNonferrous AlloysSlide Number 26Metal FabricationMetal FabricationMetal Fabrication Methods (i)Metal Fabrication Methods (ii)Metal Fabrication Methods (iii)Metal Fabrication Methods (v)Metal Fabrication Methods (vi)Thermal Processing of MetalsThermal Processing of MetalsHeat Treatment Temperature-Time PathsHardenability -- SteelsHardenability -- SteelsReason Why Hardness Changes with DistanceHardenability vs Alloy Composition Precipitation StrengtheningPrecipitation HardeningInfluence of Precipitation Heat Treatment on TS, %ELSummaryChapter 12: Structures & Properties of CeramicsAtomic Bonding in CeramicsFactors that Determine Crystal StructureCoordination Number and Ionic RadiiComputation of Minimum Cation-Anion Radius RatioExample Problem: Predicting the Crystal Structure of FeORock Salt StructureMgO and FeOAX Crystal StructuresABX3 Crystal StructuresSilicate CeramicsPolymorphic Forms of CarbonPolymorphic Forms of Carbon (cont)Polymorphic Forms of Carbon (cont) Fullerenes and NanotubesFactors that Determine Crystal StructurePoint Defects in Ceramics (i)Point Defects in Ceramics (ii)Ceramic Phase DiagramsMechanical PropertiesSUMMARYHomework IV AssignmentCoordination Number and Ionic RadiiChapter 14:Polymer StructuresWhat is a Polymer?Natural PolymersPolymer CompositionSlide Number 7Unsaturated HydrocarbonsChemistry and Structure of PolyethyleneIsomerismBulk or Commodity PolymersMolecular Structures for PolymersPolymers Molecular ShapeChain End-to-End Distance, rPolymer CrystallinityCrystallinity in PolymersPolymer Crystallinity (cont.)Semicrystalline PolymersMOLECULAR WEIGHTMOLECULAR WEIGHT DISTRIBUTIONDegree of Polymerization, DP CopolymersChapter 15: Characteristics, Applications & Processing of PolymersMechanical Properties of Polymers Stress-Strain BehaviorMechanical Properties of Polymers Stress-Strain BehaviorMechanisms of DeformationBrittle Crosslinked and Network Polymers Mechanisms of Deformation Semicrystalline (Plastic) Polymers Predeformation by DrawingMechanisms of DeformationElastomersThermoplastics vs. ThermosetsThermoplastics vs. ThermosetsInfluence of T and Strain Rate on Thermoplastics Melting & Glass Transition Temps.Time-Dependent DeformationPolymer FormationAddition (Chain) PolymerizationPolymer AdditivesPolymer Additives (cont.)Processing of PlasticsSlide Number 18Processing Plastics Compression MoldingProcessing Plastics Injection MoldingProcessing Plastics ExtrusionProcessing Plastics Blown-Film ExtrusionPolymer Types FibersPolymer Types MiscellaneousAdvanced PolymersAdvanced PolymersSummarySummary