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Callister - An introduction - 8th edition

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9.11 Binary Eutectic Systems • 301<br />

40 wt% Pb. Figure 9.8 indicates that an alloy of this composition is completely<br />

molten at about 185C (365F), which makes this material especially attractive as a<br />

low-temperature solder, because it is easily melted.<br />

Concept Check 9.4<br />

At 700C (1290F), what is the maximum solubility (a) of Cu in Ag? (b) Of Ag in Cu?<br />

[The answer may be found at www.wiley.com/college/callister (Student Companion Site).]<br />

Concept Check 9.5<br />

The following is a portion of the H 2 O–NaCl phase diagram:<br />

10<br />

50<br />

Liquid<br />

(brine)<br />

40<br />

0<br />

30<br />

Temperature (°C)<br />

10<br />

Ice<br />

<br />

Liquid<br />

(brine)<br />

Salt<br />

<br />

Liquid<br />

(brine)<br />

20<br />

10<br />

Temperature (°F)<br />

20<br />

0<br />

NaCl<br />

H 2 O<br />

Ice Salt<br />

30<br />

0 10 20<br />

30<br />

100 90 80 70<br />

Composition (wt%)<br />

10<br />

20<br />

(a) Using this diagram, briefly explain how spreading salt on ice that is at a temperature<br />

below 0C (32F) can cause the ice to melt.<br />

(b) At what temperature is salt no longer useful in causing ice to melt?<br />

[The answer may be found at www.wiley.com/college/callister (Student Companion Site).]<br />

EXAMPLE PROBLEM 9.2<br />

Determination of Phases Present and Computation<br />

of Phase Compositions<br />

For a 40 wt% Sn–60 wt% Pb alloy at 150C (300F), (a) what phase(s) is (are)<br />

present? (b) What is (are) the composition(s) of the phase(s)?<br />

Solution<br />

(a) Locate this temperature–composition point on the phase diagram (point<br />

B in Figure 9.9). Inasmuch as it is within the a b region, both and b phases<br />

will coexist.

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