Page 66 - Mechanical Behavior of Materials

Section 3.2 Alloying and Processing of Metals 67

Table 3.1 Properties and Uses for Selected Engineering Metals and their Alloys

Melting Elastic Typical
Metal Temp. Density Modulus Strength Uses; Comments
T m ρ E σ u
◦ C g/cm 3 GPa MPa
3
3
◦
( F) (lb/ft ) (10 ksi) (ksi)
Iron (Fe) 1538 7.87 212 200 to 2500 Diverse: structures, machine and
and steel (2800) (491) (30.7) (30 to 360) vehicle parts, tools. Most widely
used engineering metal.
Aluminum 660 2.70 70 140 to 550 Aircraft and other lightweight
(Al) (1220) (168) (10.2) (20 to 80) structure and parts.
Titanium 1670 4.51 120 340 to 1200 Aircraft structure and engines;
(Ti) (3040) (281) (17.4) (50 to 170) industrial machine parts; surgical implants.
Copper 1085 8.93 130 170 to 1400 Electrical conductors; corrosion-
(Cu) (1985) (557) (18.8) (25 to 200) resistant parts, valves, pipes.
Alloyed to make bronze and brass.
Magnesium 650 1.74 45 170 to 340 Parts for high-speed machinery;
(Mg) (1200) (108) (6.5) (25 to 50) aerospace parts.
Nickel 1455 8.90 210 340 to 1400 Jet engine parts; alloying addition
(Ni) (2650) (556) (30.5) (50 to 200) for steels.
Cobalt 1495 8.83 211 650 to 2000 Jet engine parts; wear resistant
(Co) (2720) (551) (30.6) (95 to 300) coatings; surgical implants.
Tungsten 3422 19.3 411 120 to 650 Electrodes, light bulb filaments,
(W) (6190) (1200) (59.6) (17 to 94) flywheels, gyroscopes.
Lead 328 11.3 16 12 to 80 Corrosion resistant piping; weights,
(Pb) (620) (708) (2.3) (2 to 12) shot. Alloyed with tin in solders.

Notes: The values of T m , ρ,and E are only moderately sensitive to alloying. Ranges for σ u and uses include
◦
alloys based on these metals. Properties ρ, E,and σ u are at room temperature, except σ u is at 1650 Cfor
tungsten.
Source: Data in [Davis 98] and [Boyer 85].

influence such processing in a desirable way. Metals that are subjected to deformation as the final
processing step are termed wrought metals to distinguish them as a group from cast metals.
The details of alloying and processing are chosen so that the material has appropriate
temperature resistance, corrosion resistance, strength, ductility, and other required characteristics
for its intended use. Recalling that plastic deformation is due to the motion of dislocations, the
yield strength of a metal or alloy can usually be increased by introducing obstacles to dislocation
motion. Such obstacles can be tangles of dislocations, grain boundaries, distorted crystal structure
due to impurity atoms, or small particles dispersed in the crystal structure. Some of the principal
processing methods used for strengthening metals are listed, along with the type of obstacle, in
Table 3.2. We will now discuss each of these methods.