Chapter 10:
Phase Transformations
ISSUES TO ADDRESS ...
• Transforming one phase into another takes time.
Fe
γ
(Austenite)
C
FCC
Fe C
3
Eutectoid
transformation (cementite)
+
α
(ferrite)
(BCC)
• How does the rate of transformation depend on
time and T?
• How can we slow the transformation so that
we can engineer non-equilibrium structures?
• Are the properties of non-equilibrium
structures improved?
Fraction of Transformation
• Fraction transformed depends on time.
1
y
0.5
Avrami Eqn.
−ktn
−
=
y 1 e
fraction
transformed
time
Adapted from
Fig. 10.1,
Callister 6e.
Fixed
T
t
log (t)
0.5
0
• Transformation rate depends on T.
t
0.5
43
°C
−
= Ae Q /RT
5°
C
1
11
119°C
103°C
2°
C
88
°C
r=
Ex: recrystallization of Cu
y (%)
100
13
activation energy
50
0
1
10
• r often small: equil not possible!
102
104
log (t) min
Adapted from Fig.
10.2, Callister 6e.
(Fig. 10.2 adapted
from B.F. Decker
and D. Harker,
"Recrystallization in
Rolled Copper",
Trans AIME, 188,
1950, p. 888.)
Transformations and Undercooling
• Eutectoid transf. (Fe-C System): γ ⇒ α + Fe3 C
• Can make it occur at:
0.77wt%C
6.7wt%C
0.022wt%C
...727ºC (cool it slowly)
...below 727ºC (“undercool” it!)
T(°C)
1600
L
1400
1200
γ+L
γ
austenite
L+Fe3C
Eutectoid: γ+Fe3C
γ
α+
800
Equil. cooling: Ttransf. = 727ºC
600
∆T
α+Fe3C
Undercooling by ∆T: Ttransf. < 727ºC
1
2
3
4
5
6
Co, wt% C
6.7
727°C
0.77
400
0
(Fe)
0.022
α
ferrite
1000
Adapted from Fig.
9.21,Callister 6e. (Fig.
9.21 adapted from Binary
Alloy Phase Diagrams,
2nd ed., Vol. 1, T.B.
Massalski (Ed.-in-Chief),
ASM International,
Materials Park, OH, 1990.)
Fe3C
cementite
Eutectoid Transformation Rate ~ ∆T
• Growth of pearlite from austenite:
cementite (Fe3C)
ferrite (α)
• Reaction rate
increases with
∆T.
γ
pearlite
growth
direction
50
0
γ
α
650°C
50
675°C
(∆T smaller)
1
γ
Adapted from
Fig. 9.13,
Callister 6e.
α
0
100
600°C
(∆T larger)
α
100
10 102 103
time (s)
% austenite
α
α
γ α
α
α
α
y (% pearlite)
Austenite (γ)
grain
boundary
Diffusive flow
of C needed
Adapted from
Fig. 10.3,
Callister 6e.
Nucleation and Growth
• Reaction rate is a result of nucleation and growth
of crystals.
100
% Pearlite
Nucleation rate increases w/ ∆T
50 Nucleation
regime
0
Growth
regime
t50
Growth rate increases w/ T
log (time)
Adapted from
Fig. 10.1, Callister 6e.
• Examples:
γ
pearlite
colony
T just below TE
Nucleation rate low
Growth rate high
γ
T moderately below TE
Nucleation rate med .
Growth rate med.
γ
T way below TE
Nucleation rate high
Growth rate low
Isothermal Transformation Diagrams
y,
% transformed
• Fe-C system, Co = 0.77wt%C
• Transformation at T = 675C.
100
T=675°C
50
0
102
1
T(°C)
Austenite (stable)
700 Austenite
(unstable)
0%
10
lite
%
50 pear
0%
400
time (s)
TE (727°C)
isothermal transformation at 675°C
Pearlite
600
500
104
1
10
Adapted from Fig. 10.4,Callister 6e.
(Fig. 10.4 adapted from H. Boyer (Ed.)
Atlas of Isothermal Transformation
and Cooling Transformation Diagrams,
American Society for Metals, 1977, p.
369.)
time
102 103 104 105
(s)
Ex: Cooling History Fe-C System
• Eutectoid composition, Co = 0.77 wt%C
• Begin at T > 727 °C
• Rapidly cool to 625 °C and hold isothermally.
T(°C)
Austenite (stable)
TE (727°C)
700
Adapted from Fig.
10.5,Callister 6e.
(Fig. 10.5 adapted from
H. Boyer (Ed.) Atlas of
Pearlite
600
γ γ
γ γ
0%
10
%
50
ite
arl
pe
0%
500
γ
1
10
γ
Isothermal
Transformation and
Cooling Transformation
Diagrams, American
γ
Society for Metals,
1997, p. 28.)
102
103
104
105
time (s)
Pearlite Morphology
Two cases:
• Ttransf just below TE
• Ttransf well below TE
--Smaller T: diffusion is slower
--Pearlite is finer.
10µm
--Larger T: diffusion is faster
--Pearlite is coarser.
Adapted from Fig. 10.6 (a) and (b),Callister 6e. (Fig. 10.6 from R.M. Ralls et al., An Introduction to
Materials Science and Engineering, p. 361, John Wiley and Sons, Inc., New York, 1976.)
- Smaller ∆T:
colonies are
larger
- Larger ∆T:
colonies are
smaller
Non-Equil. Transformation Products: Fe-C
• Bainite:
--α lathes (stripes) with long
rods of Fe3C
--diffusion controlled.
• Isothermal Transf. Diagram
800
Austenite (stable)
T(°C)
A
100% pearlite
pearlite/bainite boundary
100% bainite
400
B
A
103
0%
10
10
%
50
10-1
0%
200
α (ferrite)
TE
P
600
Fe3C
(cementite)
105
time (s)
5 µm
(Adapted from Fig. 10.8, Callister, 6e.
(Fig. 10.8 from Metals Handbook, 8th ed.,
Vol. 8, Metallography, Structures, and
Phase Diagrams, American Society for
Metals, Materials Park, OH, 1973.)
Bainite reaction rate:
rbainite = e −Q / RT
Adapted from Fig. 10.9,Callister 6e.
(Fig. 10.9 adapted from H. Boyer (Ed.) Atlas of Isothermal Transformation and
Cooling Transformation Diagrams, American Society for Metals, 1997, p. 28.)
Other Products: Fe-C System (1)
• Spheroidite:
α
--α crystals with spherical Fe3C
(ferrite)
--diffusion dependent.
--heat bainite or pearlite for long times
--reduces interfacial area (driving force) Fe3C
• Isothermal Transf. Diagram
800
Austenite (stable)
T(°C)
A
P
600
400
(cementite)
TE
100% spheroidite
Spheroidite
B
A
103
%
100
50%
10
(Adapted from Fig. 10.10, Callister,
6e. (Fig. 10.10 copyright United
States Steel Corporation, 1971.)
Adapted from Fig. 10.9,Callister 6e.
(Fig. 10.9 adapted from H. Boyer (Ed.) Atlas of
0%
200
10-1
100% spheroidite
60 µm
Isothermal Transformation and Cooling
Transformation Diagrams, American Society for
Metals, 1997, p. 28.)
105 time
(s)
Other Products: Fe-C System (2)
• Martensite:
--γ(FCC) to Martensite (BCT)
Fe atom
sites
x
x
x
60 µm
(involves single atom jumps)
potential
C atom sites
x
x
x
(Adapted from Fig.
10.11, Callister, 6e.
• Isothermal Transf. Diagram
800
T(°C)
Austenite (stable)
A
600
Adapted
from Fig.
10.13,
400
TE
P
(Adapted from Fig. 10.12, Callister,
6e. (Fig. 10.12 courtesy United
States Steel Corporation.)
S
A
B
Callister 6e.
%
50
0%
200
Martentite needles
Austenite
• γ to M transformation..
10
0%
M+A
M+A
M+A
10
10-1
103
0%
50%
90%
105
-- is rapid!
-- % transf. depends on T only.
time (s)
Time-Temperature-Transformation (TTT) Diagrams
Isothermal TTT Diagram
Continuous Cooling TTT Diagram
TTT Diagrams for a Eutectoid Steel
Cooling Ex: Fe-C System (1)
• Co = Ceutectoid
• Three histories...
Rapid Hold Rapid Hold Rapid
cool to: for: cool to: for: cool to:
350°C 104s Troom 104s Troom
250°C 102s Troom 102s Troom
650°C 20s 400°C 103s Troom
Case I
800
Austenite (stable)
T(°C)
A
600
A
P
S
B
400
10
100%A
%
50
0%
200 M + A
M+A
M+A
10
10-1
103
100%B
0%
0%
50%
90%
Adapted
from Fig.
10.15,
Callister 6e.
100% Bainite
105 time (s)
Cooling Ex: Fe-C System (2)
•
Co = Ceutectoid
•
Three histories...
Rapid Hold Rapid Hold Rapid
cool to: for: cool to: for: cool to:
350°C 104s Troom 104s Troom
250°C 102s Troom 102s Troom
Case II
800
Austenite (stable)
T(°C)
A
650°C 20s 400°C
P
600
S
A
B
400
0%
%
200 M + A
M+A
M+A
10
10-1
50
100%A
10
0%
0%
50%
90%
Adapted
from Fig.
10.15,
Callister 6e.
M + trace of A
103
105 time (s)
103s Troom
Cooling Ex: Fe-C System (3)
•
Co = Ceutectoid
•
Three histories...
Rapid Hold Rapid Hold Rapid
cool to: for: cool to: for: cool to:
350°C 104s Troom 104s Troom
Case III
800
Austenite (stable)
T(°C)
A
100%A
600
A
50%P, 50%A
P
S
B
400
50%P, 50%B
50%P, 50%A
%
50
0%
200 M + A
M+A
M+A
10
10-1
250°C 102s Troom 102s Troom
650°C 20s 400°C 103s Troom
10
0%
0%
50%
90%
Adapted
from Fig.
10.15,
Callister 6e.
50
103 %P 105 time (s)
,5
0%
B
Mechanical Prop: Fe-C System (1)
• Effect of wt%C
Adapted from Fig. 9.27,Callister
6e. (Fig. 9.27 courtesy Republic
Steel Corporation.)
TS(MPa)
1100
YS(MPa)
Co<0.77wt%C
Hypoeutectoid
Hypo
Hyper
Co>0.77wt%C
Hypereutectoid
%EL
Hypo
Hyper
80
100
900
Adapted from Fig. 9.30,Callister
6e. (Fig. 9.30 copyright 1971 by
United States Steel Corporation.)
hardness
40
700
50
500
0
0.5
1
0
0.77
0
0.77
300
1
Impact energy (Izod, ft-lb)
Pearlite (med)
ferrite (soft)
Pearlite (med)
Cementite
(hard)
0.5
0
wt%C
wt%C
• More wt%C: TS and YS increase, %EL decreases.
Adapted from Fig.
10.20, Callister 6e.
(Fig. 10.20 based on
data from Metals
Handbook: Heat
Treating, Vol. 4, 9th
ed., V. Masseria
(Managing Ed.),
American Society for
Metals, 1981, p. 9.)
Mechanical Prop: Fe-C System (2)
• Fine vs coarse pearlite vs spheroidite
Hyper
Brinell hardness
320
240
fine
pearlite
160
coarse
pearlite
spheroidite
80
0
0.5
1
wt%C
90
Ductility (%AR)
Hypo
Hypo
spheroidite
60
coarse
pearlite
fine
pearlite
30
0
0
• Hardness: fine > coarse > spheroidite
• %AR:
fine < coarse < spheroidite
Hyper
0.5
1
wt%C
Adapted from Fig. 10.21, Callister
6e. (Fig. 10.21 based on data from
Metals Handbook: Heat Treating,
Vol. 4, 9th ed., V. Masseria
(Managing Ed.), American Society
for Metals, 1981, pp. 9 and 17.)
Mechanical Prop: Fe-C System (3)
• Fine Pearlite vs Martensite:
Brinell hardness
Hypo
600
Hyper
martensite
Adapted from Fig. 10.23,
Callister 6e. (Fig. 10.23
adapted from Edgar C. Bain,
400
Functions of the Alloying
Elements in Steel, American
200
0
0
fine pearlite
0.5
Society for Metals, 1939, p.
36; and R.A. Grange, C.R.
Hribal, and L.F. Porter, Metall.
Trans. A, Vol. 8A, p. 1776.)
1
wt%C
• Hardness: fine pearlite << martensite.
Tempering Martensite
• reduces brittleness of martensite,
• reduces internal stress caused by quenching.
TS(MPa)
YS(MPa)
1800
Adapted from
Fig. 10.25,
1400
Callister 6e.
(Fig. 10.25
1200
adapted from
Fig. furnished
courtesy of 1000
Republic Steel
Corporation.) 800
200
TS
YS
60
50
%AR
40
30
%AR
400
9 µm
1600
Adapted from
Fig. 10.24,
Callister 6e.
(Fig. 10.24
copyright by
United States
Steel
Corporation,
1971.)
600
Tempering T (°C)
• produces extremely small Fe3C particles surrounded by α.
• decreases TS, YS but increases %AR
Summary: Processing Options
Austenite (γ)
slow
cool
Pearlite
moderate
cool
Bainite
Martensite
T Martensite
bainite
fine pearlite
coarse pearlite
spheroidite
rapid
quench
Martensite
(BCT phase
diffusionless
transformation)
reheat
Ductility
Strength
(α + Fe3C layers + a (α + Fe3C plates/needles)
proeutectoid phase)
Adapted from
Fig. 10.27,
Callister 6e.
General Trends
Tempered
Martensite
(α + very fine
Fe3C particles)
Chapter 11: Metal Alloys
Applications and Processing
ISSUES TO ADDRESS...
• How are metal alloys classified and how are they used?
• What are some of the common fabrication techniques?
• How do properties vary throughout a piece of material
that has been quenched, for example?
• How can properties be modified by post heat treatment?
Taxonomy of Metals
Metal Alloys
Ferrous
Steels
Steels
<1.4wt%C
<1.4wt%C
Cast Irons
Cast
Irons
3-4.5wt%C
3-4.5wt%C
Cu
Al
1600
δ
L
1400
γ+L
γ
austenite
L+Fe3C
1148°C
Eutectic:
4.30
1000
γ
α+
α800
ferrite
600
400
0
(Fe)
γ+Fe3C
727°C
1
α+Fe3C
2
3
4
Ti
Adapted from Fig. 9.21,Callister 6e.
(Fig. 9.21 adapted from Binary
Alloy Phase Diagrams, 2nd ed.,
Vol. 1, T.B. Massalski (Ed.-in-Chief),
ASM International, Materials Park,
OH, 1990.)
Fe3C
cementite
Eutectoid:
0.77
Mg
microstructure:
ferrite, graphite
cementite
T(°C)
1200
Adapted from
Fig. 11.1,
Callister 6e.
Nonferrous
5
6
Co, wt% C
6.7
Steels
High Alloy
Low Alloy
low carbon med carbon
high carbon
<0.25wt%C 0.25-0.6wt%C 0.6-1.4wt%C
heat
plain
treatable
Cr,V
Cr, Ni
Additions none
none
none
Ni, Mo
Mo
Example 1010 4310 1040
4340 1095
Hardenability 0
+
+
++
++
TS
0
+
++
+
EL
+
+
0
Name
plain HSLA
Uses
auto
bridges
struc. towers
sheet press.
vessels
plain
pistons wear
crank
gears
shafts
applic.
wear
bolts
hammers applic.
blades
tool
Cr, V,
Mo, W
4190
+++
++
-drills
saws
dies
increasing strength, cost, decreasing ductility
Based on data provided in Tables 11.1(b), 11.2(b), 11.3, and 11.4, Callister 6e.
austentitic
stainless
Cr, Ni, Mo
304
0
0
++
high T
applic.
turbines
furnaces
V. corros.
resistant
Basic Ideas in Alloying Steels:
1. Phase Partitioning at Austenite/Pearlite Interface
Carbide Formers
V, Ti, Nb
Ferrite Formers (solid solution)
Ni, Si, Mn
Paritioning at the Austenite/Pearlite Interface
Slows transformation
Allows Bainite or Martensite to form on cooling
Basic Ideas in Alloying Steels:
2. Alloying to Control the Eutectoid Transformation
Alloying
Control ‘Nose’ in TTT Diagram
Control Eutectoid Temperature and C Composition
Cr: added (~8 – 12wt %) to make steel ‘stainless’
Ni: High concentrations to stabilize austenite – austenitic steels
Hardenability of Steels
• Ability to form martensite
• Jominy end quench test to measure hardenability.
1”
specimen
(heated to γ
phase field)
24°C water
flat ground
4”
Adapted from Fig. 11.10,
Callister 6e. (Fig. 11.10
adapted from A.G. Guy,
Essentials of Materials
Science, McGraw-Hill
Book Company, New
York, 1978.)
Hardness, HRC
• Hardness versus distance from the quenched end.
Adapted from Fig. 11.11,
Callister 6e.
Distance from quenched end
Why Hardness Changes with Position
Hardness, HRC
• The cooling rate varies with position.
60
40
20
0
1
2
3
distance from quenched end (in)
T(°C)
600
A→
0%
100%
P
Adapted from Fig. 11.12, Callister 6e.
(Fig. 11.12 adapted from H. Boyer
(Ed.) Atlas of Isothermal
400
200
Transformation and Cooling
Transformation Diagrams, American
M(start)
Society for Metals, 1977, p. 376.)
A→M
1
te
rli
ite ea
e rl P
lit ea +
ar e P ite
Pe in ens e
F
t t
ar si
M ten
ar
0.1
M
0 M(finish)
10
100
1000
Time (s)
Hardenability vs. Alloy Content
• "Alloy Steels"
(4140, 4340, 5140, 8640)
--contain Ni, Cr, Mo
(0.2 to 2wt%)
--these elements shift
the "nose".
--martensite is easier
to form.
10
3
60
2 Cooling rate (°C/s)
100
4340
80
%M
50
40
4140
8640
40
10
Adapted from Fig. 11.13, Callister 6e.
(Fig. 11.13 adapted from figure
furnished courtesy Republic Steel
Corporation.)
100
Hardness, HRC
• Jominy end quench
results, C = 0.4wt%C
5140
20
0 10 20 30 40 50
Distance from quenched end (mm)
800
T(°C)
600
A
400
200
0 -1
10 10
B
TE
shift from
A to B due
to alloying
M(start)
M(90%)
103 105 Time (s)
Quenching Medium and Geometry
• Effect of quenching medium:
Medium
air
oil
water
Severity of Quench
small
moderate
large
Hardness
small
moderate
large
• Effect of geometry:
When surface-to-volume ratio increases:
--cooling rate increases
--hardness increases
Position Cooling rate
center
small
surface
large
Hardness
small
large
Nonferrous Alloys
• Cu Alloys
• Al Alloys
Brass: Zn is subst. impurity -lower ρ: 2.7g/cm3
(costume jewelry, coins,
-Cu, Mg, Si, Mn, Zn additions
corrosion resistant)
-solid sol. or precip.
Bronze: Sn, Al, Si, Ni are
strengthened (struct.
subst. impurity
aircraft parts
(bushings, landing
& packaging)
gear)
• Mg Alloys
NonFerrous
Cu-Be:
-very low ρ: 1.7g/cm3
Alloys
precip. hardened
-ignites easily
for strength
-aircraft, missles
• Ti Alloys
-lower ρ: 4.5g/cm3
• Refractory metals
-high melting T
-Nb, Mo, W, Ta
vs 7.9 for steel
• Noble metals
-reactive at high T -Ag, Au, Pt
-oxid./corr. resistant
-space applic.
Based on discussion and data provided in Section 11.3, Callister 6e.
Metal Fabrication Methods (1)
CASTING
FORMING
• Forging
(wrenches, crankshafts)
force
JOINING
• Rolling
(I-beams, rails)
roll
die
Ao blank
Ad often at
elev. T
• Drawing
force
Ao
die
Ad
roll
• Extrusion
(rods, wire, tubing)
die
Ao
Adapted from
Fig. 11.7,
Callister 6e.
(rods, tubing)
Ao
tensile
force
Ad
force
container
ram
billet
container
die holder
extrusion
die
Ad
Forming Temperature
• Hot working
--recrystallization
• Cold working
--recrystallization
--less energy to deform
--oxidation: poor finish
--lower strength
--less energy to deform
--oxidation: poor finish
--lower strength
• Cold worked microstructures
--generally are very anisotropic!
--Forged
(a)
--Swaged
(b)
--Fracture resistant!
(c)
Reprinted w/ permission from R.W. Hertzberg, "Deformation and Fracture Mechanics of Engineering
Materials", (4th ed.), John Wiley and Sons, Inc., 1996. (a) Fig. 10.5, p. 410 (micrograph courtesy of G.
Vander Voort, Car Tech Corp.); (b) Fig. 10.6(b), p. 411 (Orig. source: J.F. Peck and D.A. Thomas,
Trans. Metall. Soc. AIME, 1961, p. 1240); (c) Fig. 10.10, p. 415 (Orig. source: A.J. McEvily, Jr.
and R.H. Bush, Trans. ASM 55, 1962, p. 654.)
Metal Fabrication Methods (2)
FORMING
CASTING
• Sand Casting
(large parts, e.g.,
auto engine blocks)
Sand
• Die Casting
(high volume, low T alloys)
Sand
molten metal
• Investment Casting
(low volume, complex shapes
e.g., jewelry, turbine blades)
plaster
die formed
around wax
prototype
JOINING
• Continuous Casting
(simple slab shapes)
molten
solidified
wax
Metal Fabrication Methods (3)
FORMING
• Powder Processing
(materials w/low ductility)
pressure
heat
area
contact
densify
point contact
at low T
densification
by diffusion at
higher T
CASTING
JOINING
• Welding
(when one large part is
impractical)
filler metal (melted)
base metal (melted)
fused base metal
heat affected zone
unaffected
unaffected
Adapted from Fig.
piece 1 piece 2
11.8, Callister 6e.
(Fig. 11.8 from
• Heat affected zone:
Iron Castings
Handbook, C.F.
Walton and T.J.
(region in which the
Opar (Ed.), 1981.)
microstructure has been
changed).
Thermal Processing of Metals
Annealing: Heat to Tanneal, then cool slowly.
• Stress Relief: Reduce
stress caused by:
-plastic deformation
-nonuniform cooling
-phase transform.
• Spheroidize (steels):
Make very soft steels for
good machining. Heat just
below TE & hold for
15-25h.
Types of
Annealing
• Process Anneal:
Negate effect of
cold working by
(recovery/
recrystallization)
Based on discussion in Section 11.7, Callister 6e.
• Full Anneal (steels):
Make soft steels for
good forming by heating
to get γ, then cool in
furnace to get coarse P.
• Normalize (steels):
Deform steel with large
grains, then normalize
to make grains small.
Precipitation Hardening
• Particles impede dislocations.
700
• Ex: Al-Cu system
T(°C)
• Procedure:
600
α
α+L
--Pt A: solution heat treat
A
500
(get α solid solution)
--Pt B: quench to room temp.400 C
--Pt C: reheat to nucleate
small θ crystals within
300
0 B 10
α crystals.
(Al)
θ+L
α+θ
20
30
θ
50
wt%Cu
Adapted from Fig. 11.22, Callister 6e. (Fig. 11.22 adapted
from J.L. Murray, International Metals Review 30, p.5, 1985.)
Temp.
Pt A (sol’n heat treat)
Adapted from Fig.
11.20, Callister 6e.
40
CuAl2
composition range
needed for precipitation hardening
• Other precipitation
systems:
• Cu-Be
• Cu-Sn
• Mg-Al
L
Pt C (precipitate θ)
Pt B
Time
Precipitate Effect on TS, %El
• 2014 Al Alloy:
500
400
300
200
• %EL reaches minimum
with precipitation time.
few
p
e
“o recip r lar
ve
ra itate ge
ge
d” s
%EL (2in sample)
no
so n-eq
lid ui
so l .
lut
i on
ma
p r ny s
ec
ipi mall
“a tates
ge
d”
tensile strength (MPa)
• TS peaks with
precipitation time.
• Increasing T accelerates
process.
149°C
204°C
1min
1h 1day 1mo 1yr
precipitation heat treat time (h)
30
20
10
204°C
0
1min
1h 1day 1mo 1yr
precipitation heat treat time (h)
Adapted from Fig. 11.25 (a) and (b), Callister 6e. (Fig. 11.25 adapted from Metals Handbook:
Properties and Selection: Nonferrous Alloys and Pure Metals, Vol. 2, 9th ed., H. Baker
(Managing Ed.), American Society for Metals, 1979. p. 41.)
149°C
SUMMARY
• Steels: increase TS, Hardness (and cost) by adding
--C (low alloy steels)
--Cr, V, Ni, Mo, W (high alloy steels)
--ductility usually decreases w/additions.
• Non-ferrous:
--Cu, Al, Ti, Mg, Refractory, and noble metals.
• Fabrication techniques:
--forming, casting, joining.
• Hardenability
--increases with alloy content.
• Precipitation hardening
--effective means to increase strength in
Al, Cu, and Mg alloys.