Fundamentals of Materials Science and Engineering: An Integrated Approach, 3e

GTBL042-08 GTBL042-Callister-v3 October 4, 2007 11:51

2nd Revised Pages

8.11 Strain Hardening • 261

Yield strength (MPa) Yield strength (ksi)Tensile strength (MPa) Tensile strength (ksi)

800

700

600

500

400

300

200

100

900

800

700

600

500

400

300

200

120

100

80

60

40

20

140

120

100

80

60

40

0 10 20 30 40 50 60 70 0 10 20 30 40 50 60 70

Percent cold work Percent cold work

(a)

010203040506070

Percent cold work

(c)

(b)

1040 Steel

Brass

Copper

1040 Steel

Brass

Copper

1040 Steel

Brass

Copper

Ductility (%EL)

70

60

50

40

30

20

10

0

Figure 8.19 For 1040 steel, brass, and copper, (a) the

increase in yield strength, (b) the increase in tensile

strength, and (c) the decrease in ductility (%EL) with

percent cold work. [Adapted fromMetals Handbook:

Properties and Selection: Irons and Steels,Vol. 1, 9th edition,

B. Bardes (Editor), American Society for Metals, 1978,

p. 226; andMetals Handbook: Properties and Selection:

Nonferrous Alloys and Pure Metals,Vol. 2, 9th edition,

H. Baker (Managing Editor), American Society for Metals,

1979, pp. 276 and 327.]

whereA 0 is the original area of the cross section that experiences deformation and

Adis the area after deformation.

Figures 8.19aand 8.19bdemonstrate how steel, brass, and copper increase in

yield and tensile strength with increasing cold work. The price for this enhancement

of hardness and strength is in the ductility of the metal. This is shown in Figure 8.19c,

in which the ductility, in percent elongation, experiences a reduction with increasing