The Science and Engineering
of Materials, 4th ed
Donald R. Askeland – Pradeep P. Phulé
Chapter 13 – Nonferrous Alloys
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Objectives of Chapter 13
 Explore the properties and applications of
Cu, Al, and Ti alloys in load-bearing
applications.
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Chapter Outline
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
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13.1
13.2
13.3
13.4
13.5
13.6
Aluminum Alloys
Magnesium and Beryllium Alloys
Copper Alloys
Nickel and Cobalt Alloys
Titanium Alloys
Refractory and Precious Metals
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Section 13.1
Aluminum Alloys
 Hall-Heroult process - An electrolytic process by which
aluminum is extracted from its ore.
 Temper designation - A shorthand notation using letters
and numbers to describe the processing of an alloy. H
tempers refer to cold-worked alloys; T tempers refer to
age-hardening treatments.
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Figure 13.1
Production of
aluminum in an
electrolytic cell.
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Figure 13.2 (a) FeAl3 inclusions in annealed 1100
aluminum ( 350). (b) Mg2Si precipitates in annealed
5457 aluminum alloy ( 75). (From ASM Handbook,
Vol. 7, (1972), ASM International, Materials Park, OH
44073.)
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Figure 13.3 Portion of the aluminum-magnesium
phase diagram.
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Figure 13.4 (a) Sand-cast 443 aluminum alloy containing
coarse silicon and inclusions. (b) Permanent-mold 443 alloy
containing fine dendrite cells and fine silicon due to faster
cooling. (c) Die-cast 443 alloy with a still finer microstructure
( 350). (From ASM Handbook, Vol. 7, (1972), ASM
International, Materials Park, OH 44073.)
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Example 13.1
Strength-to-Weight Ratio in Design
A steel cable 0.5 in. in diameter has a yield strength of 70,000
psi. The density of steel is about 7.87 g/cm3. Based on the data
in Table 13-5, determine (a) the maximum load that the steel
cable can support, (b) the diameter of a cold-worked
aluminum-manganese alloy (3004-H 18) required to support
the same load as the steel, and (c) the weight per foot of the
steel cable versus the aluminum alloy cable.
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Example 13.1 SOLUTION
a. Load = F = σy  A = 70.000 (π/4) (0.5 in.)2 = 13,744 lb
b. The yield strength of the aluminum alloy is 36,000 psi.
Thus:
A = (π/4)d2 = F/σy = 13,744/36,000 = 0.38 in.2
d = 0.697 in.
Density of steel = ρ = 7.87 g/cm3 = 0.284 lb/in.3
Density of aluminum = ρ = 2.70 g/cm3 = 0.097 lb/in3
c. Weight of steel = Alρ = (π/4)(0.5in)2(12)(0284)
= 0.669 lb/ft
Weight of aluminum = Alρ = (π/4)(0.697)2 (2) (12)
(0.097) = 0.444 lb/ft
Although the yield strength of the aluminum is lower than
that of the steel and the cable must be larger in diameter,
the aluminum cable weighs only about half as much as the
steel cable. When comparing materials, a proper factor-ofsafety should also be included during design.
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Example 13.2
Design of an Aluminum Recycling Process
Design a method for recycling aluminum alloys used for beverage
cans.
Example 13.2 SOLUTION
One approach to recycling the cans is to separate the two alloys from
the cans. The cans are shredded, then heated to remove the lacquer
that helps protect the cans during use. We could then further shred
the material at a temperature where the 5182 alloy begins to melt.
The small pieces of 5182 can therefore be separated by passing the
material through a screen. The two separated alloys can then be
melted, cast, and rolled into new can stock.
An alternative method would be to simply remelt the cans.
Once the cans have been remelted, we could bubble chlorine gas
through the liquid alloy. The chlorine reacts selectively with the
magnesium, removing it as a chloride. The remaining liquid can then
be adjusted to the proper composition and be recycled as 3004 alloy.
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Example 13.3
Design/Materials Selection for
a Cryogenic Tank
Design the material to be used to contain liquid hydrogen fuel
for the space shuttle.
Example 13.3 SOLUTION
Liquid hydrogen is stored below 253oC; therefore, our tank must
have good cryogenic properties.
Lightweight aluminum would appear to be a good choice.
Aluminum does not show a ductile to brittle transition. Because
of its good ductility, we expect aluminum to also have good
fracture toughness, particularly when the alloy is in the
annealed condition.
One of the most common cryogenic aluminum alloys is
5083-O. Aluminum-lithium alloys are also being considered for
low-temperature applications to take advantage of their even
lower density.
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Example 13.4
Design of a Casting Process for Wheels
Design a casting process to produce automotive wheels having
reduced weight and consistent and uniform properties.
Example 13.4 SOLUTION
Thixocasting process in which the material is stirred
during solidification, producing a partly liquid, partly solid structure
that behaves as a solid when no external force is applied, yet flows
as a liquid under pressure. We would select an alloy with a widefreezing range so that a significant portion of the solidification
process occurs by the growth of dendrites. A hypoeutectic
aluminum-silicon alloy might be appropriate. In the thixocasting
process, the dendrites are broken up by stirring during
solidification. The billet is later reheated to cause melting of just
the eutectic portion of the alloy, and it is then forced into the mold
in its semi-solid condition at a temperature below the liquidus
temperature.
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Section 13.2
Magnesium and Beryllium Alloys
 Magnesium alloys are used in aerospace applications,
high-speed machinery, and transportation and materials
handling equipment.
 Instrument grade beryllium is used in inertial guidance
systems where the elastic deformation must be minimal;
structural grades are used in aerospace applications; and
nuclear applications take advantage of the transparency
of beryllium to electromagnetic radiation. Beryllium is
expensive, brittle, reactive, and toxic.
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Figure 13.5 The
magnesium-aluminum
phase diagram.
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Section 13.3
Copper Alloys
 Blister copper - An impure form of copper obtained
during the copper refining process.
 Applications for copper-based alloys include electrical
components (such as wire), pumps, valves, and
plumbing parts, where these properties are used to
advantage.
 Brass - A group of copper-based alloys, normally
containing zinc as the major alloying element.
 Bronze - Generally, copper alloys containing tin, can
contain other elements.
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Figure 13.6
Binary phase
diagrams for the
(a) copper-zinc,
(b) copper-tin,
(c) copperaluminum, and
(d) copperberyllium
systems.
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Example 13.5
Design/Materials Selection
for an Electrical Switch
Design the contacts for a switch or relay that opens and closes
a high-current electrical circuit.
Example 13.5 SOLUTION
When the switch or relay opens and closes, contact between
the conductive surfaces can cause wear and result in poor
contact and arcing.
Therefore, our design must provide for both good
electrical conductivity and good wear resistance. A relatively
pure copper alloy dispersion strengthened with a hard phase
that does not disturb the copper lattice would, perhaps, be
ideal. In a Cu-Al2O3 alloy, the hard ceramic-oxide particles
provide wear resistance but do not interfere with the electrical
conductivity of the copper matrix.
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Example 13.6
Design of a Heat Treatment
for a Cu-Al Alloy Gear
Design the heat treatment required to produce a high-strength
aluminum-bronze gear containing 10% Al.
Figure 13.6 Binary phase
diagrams for the (c)
copper-aluminum
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Example 13.6 SOLUTION
1. Heat the alloy to 950oC and hold to produce 100% β.
2. Quench the alloy to room temperature to cause β to
transform to martensite, β´, which is supersaturated in
copper.
3. Temper below 565oC; a temperature of 400oC might be
suitable. During tempering, the martensite transforms
to α and γ2. The amount of the γ2 that forms at 400oC is:
4. Cool rapidly to room temperature so that the
equilibrium γ does not form.
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Section 13.4
Nickel and Cobalt Alloys
 Nickel and cobalt alloys are used for corrosion protection
and for high-temperature resistance, taking advantage
of their high melting points and high strengths.
 Superalloys - A group of nickel, iron-nickel, and cobaltbased alloys that have exceptional heat resistance, creep
resistance, and corrosion resistance.
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Figure 13.7 The
effect of
temperature on the
tensile strength of
several nickelbased alloys.
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Figure 13.8 (a) Microstructure of a superalloy, with
carbides at the grain boundaries and γ΄ precipitates in
the matrix ( 15,000). (b) Microstructure of a superalloy
aged at two temperatures, producing both large and
small cubical γ΄ precipitates ( 10,000). (ASM
Handbook, Vol. 9, Metallography and Microstructure
(1985), ASM International, Materials Park, OH 44073.)
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Example 13.7
Design/Materials Selection for a
High-Performance Jet Engine Turbine Blade
Design a nickel-based superalloy for producing turbine blades
for a gas turbine aircraft engine that will have a particularly
long creep-rupture time at temperatures approaching 1100oC.
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Figure 13.9 (a) A turbine
blade designed for active
cooling by a gas. (b) The
high-temperature capability
of superalloys has increased
with improvements in
manufacturing methods (for
Example 13.7).
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Example 13.7 SOLUTION
First, we need a very stable microstructure. Addition of
aluminum or titanium permits the precipitation of up to 60
vol% of the γ´ phase during heat treatment and may
permit the alloy to operate at temperatures approaching
0.85 times the absolute melting temperature.
Second, we might produce a directionally solidified
or even single-crystal turbine blade (Chapter 8). In
directional solidification, only columnar grains.
We would then heat treat the casting to assure that the
carbides and γ´ precipitate with the correct size and
distribution.
Finally, the blade might contain small cooling
channels along its length. Air for combustion in the engine
can pass through these channels, providing active cooling
to the blade, before reacting with fuel in the combustion
chamber.
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Section 13.5
Titanium Alloys
 Titanium’s excellent corrosion resistance provides
applications in chemical processing equipment, marine
components, and biomedical implants such as hip
prostheses.
 Titanium is an important aerospace material, finding
applications as airframe and jet engine components.
 Titanium alloys are considered biocompatible (i.e., they
are not rejected by the body). By developing porous
coatings of bone-like ceramic compositions known as
hydroxyapatite, it may be possible to make titanium
implants bioactive (i.e., the natural bone can grow into
the hydroxyapatite coating).
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Figure 13.10
Portions of the
phase diagrams for
(a) titanium-tin,
(b) titaniumaluminum, (c)
titaniummolybdenum, and
(d) titaniummanganese.
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Figure 13.11
The effect of
temperature on
the yield
strength of
selected
titanium alloys.
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Figure 13.12 (a) Annealing and (b) microstructure of rapidly
cooled alpha titanium ( 100). Both the grain boundary
precipitate and the Widmanstätten plates are alpha. (From
ASM Handbook, Vol. 7, (1972), ASM International, Materials
Park, OH 44073.)
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Figure 13.13 Annealing
of an alpha-beta
titanium alloy. (a)
Annealing is done just
below the α–β
transformation
temperature, (b) slow
cooling gives equiaxed
α grains ( 250), and
(c) rapid cooling yields
acicular α grains (
2500). (From Metals
Handbook, Vol. 7,
(1972), ASM
International, Materials
Park, OH 44073.)
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Figure 13.14 (a)
Heat treatment and
(b) microstructure
of the alpha-beta
titanium alloys. The
structure contains
primary α (large
white grains) and a
dark β matrix with
needles of α formed
during aging (250).
(From ASM
Handbook, Vol. 7,
(1972), ASM
International,
Materials Park, OH
44073.)
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Example 13.8
Design of a Heat Exchanger
Design a 5-ft-diameter, 30-ft-long heat exchanger
for the petrochemical industry (Figure 13.15).
©2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning ™ is a trademark used herein
under license.
Figure 13.15 Sketch of a heat exchanger using
titanium tubes (for Example 13.8).
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Example 13.8 SOLUTION
Provided that the maximum operating temperature is below
535oC so that the oxide film is stable, titanium might be a
good choice to provide corrosion resistance at elevated
temperatures. A commercially pure titanium provides the
best corrosion resistance.
Pure titanium also provides superior forming and
welding characteristics and would, therefore, be our most
logical selection. If pure titanium does not provide
sufficient strength, an alternative is an alpha titanium alloy,
still providing good corrosion resistance, forming
characteristics, and weldability but also somewhat
improved strength.
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Example 13.9
Design of a Connecting Rod
Design a high-performance connecting rod for the engine
of a racing automobile (Figure 13.16).
Figure 13.16 Sketch of
connecting rod (for
Example 13.9).
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Example 13.9 SOLUTION
To achieve high strengths, we might consider an alphabeta titanium alloy. Because of its availability, the Ti-6%
Al-4% V alloy is a good choice. The alloy is heated to
about 1065oC, which is in the all-β portion of the phase
diagram.
When the heat treatment is performed in the all-β
region, the tempered martensite has an acicular structure,
which reduces the rate of growth of any fatigue cracks that
might develop.
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Example 13.10
Materials for Hip Prosthesis
What type of a material would you choose for an implant to be
used for a total hip replacement implant?
Example 13.10 SOLUTION
We need to consider the following factors: biocompatibility,
corrosion resistance, high-fracture toughness, excellent
fatigue life, and wear resistance.
These requirements suggest 316 stainless steel or Ti6% Al-4% V. Titanium is bio-compatible and would be a better
choice. Perhaps a composite material in which the stem is
made from a Ti-6% Al-4% V alloy and a head that is made
from a wear-resistant, corrosion resistant, and fractured tough
ceramic, such as alumina, may be an answer.
Another option is to coat the implant with a material
like porous hydroxyapatite to encourage bone growth.
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Section 13.6
Refractory and Precious Metals
 Refractory metals – These include tungsten,
molybdenum, tantalum, and niobium (or columbium),
have exceptionally high-melting temperatures (above
1925oC) and, consequently, have the potential for hightemperature service.
 Applications of Refractory metals include filaments for
light bulbs, rocket nozzles, nuclear power generators,
tantalum- and niobium-based electronic capacitors, and
chemical processing equipment.
 Precious Metals - These include gold, silver, palladium,
platinum, and rhodium.From an engineering viewpoint,
these materials resist corrosion and make very good
conductors of electricity.
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