Page 267 - Materials Science and Engineering An Introduction

7.12 Recrystallization • 239

Table 7.2
Recrystallization Melting
Recrystallization and Temperature Temperature
Melting Temperatures
for Various Metals Metal C F C F
and Alloys Lead 4 25 327 620
Tin 4 25 232 450
Zinc 10 50 420 788
Aluminum (99.999 wt%) 80 176 660 1220
Copper (99.999 wt%) 120 250 1085 1985
Brass (60 Cu– 40 Zn) 475 887 900 1652
Nickel (99.99 wt%) 370 700 1455 2651
Iron 450 840 1538 2800
Tungsten 1200 2200 3410 6170

Concept Check 7.5 Briel y explain why some metals (e.g., lead, tin) do not strain harden
when deformed at room temperature.
[The answer may be found at www.wiley.com/college/callister (Student Companion Site).]
Concept Check 7.6 Would you expect it to be possible for ceramic materials to experi-
ence recrystallization? Why or why not?
[The answer may be found at www.wiley.com/college/callister (Student Companion Site).]

DESIGN EXAMPLE 7.1

Description of Diameter Reduction Procedure
A cylindrical rod of noncold-worked brass having an initial diameter of 6.4 mm (0.25 in.) is to
be cold worked by drawing such that the cross-sectional area is reduced. It is required to have a
cold-worked yield strength of at least 345 MPa (50,000 psi) and a ductility in excess of 20%EL;
in addition, a final diameter of 5.1 mm (0.20 in.) is necessary. Describe the manner in which
this procedure may be carried out.
Solution
Let us first consider the consequences (in terms of yield strength and ductility) of cold working
in which the brass specimen diameter is reduced from 6.4 mm (designated by d 0 ) to 5.1 mm (d i ).
The %CW may be computed from Equation 7.8 as
2 2
d 0 d i
a b p - a b p
2 2
%CW = * 100
2
d 0
a b p
2
6.4 mm 2 5.1 mm 2
a b p - a b p
2 2
= * 100 = 36.5%CW
6.4 mm 2
a b p
2