callister7e_sm_ch09_8b

Prévia do material em texto

9-9 
 
 
CCu =
7.6 lbm
7.6 lbm + 144.4 lbm
× 100 = 5.0 wt% 
 
 
CZn =
144.4 lbm
7.6 lbm + 144.4 lbm
× 100 = 95.0 wt% 
 
From Figure 9.19, only the L phase is present; its composition is 95.0 wt% Zn-5.0 wt% Cu 
 
 (g) For an alloy composed of 21.7 mol Mg and 35.4 mol Pb and at 350°C, it is necessary to determine the 
Mg and Pb concentrations in weight percent. However, we must first compute the masses of Mg and Pb (in grams) 
using a rearranged form of Equation 4.4: 
 
 
mPb
' = nmPb
APb = (35.4 mol)(207.2 g/mol) = 7335 g 
 
 
mMg
' = nmMg
AMg = (21.7 mol)(24.3 g/mol) = 527 g 
 
Now, using Equation 4.3, concentrations of Pb and Mg are determined as follows: 
 
 
CPb =
7335 g
7335 g + 527 g
×100 = 93 wt% 
 
 
CMg =
527 g
7335 g + 527 g
×100 = 7 wt% 
 
From Figure 9.20, L and Mg2Pb phases are present, and 
 
 CL = 94 wt% Pb − 6 wt% Mg 
 
 
CMg2Pb
= 81 wt% Pb −19 wt% Mg 
 
 (h) For an alloy composed of 4.2 mol Cu and 1.1 mol Ag and at 900°C, it is necessary to determine the Cu 
and Ag concentrations in weight percent. However, we must first compute the masses of Cu and Ag (in grams) 
using a rearranged form of Equation 4.4: 
 
Excerpts from this work may be reproduced by instructors for distribution on a not-for-profit basis for testing or instructional purposes only to 
students enrolled in courses for which the textbook has been adopted. Any other reproduction or translation of this work beyond that permitted 
by Sections 107 or 108 of the 1976 United States Copyright Act without the permission of the copyright owner is unlawful.