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

GTBL042-10 GTBL042-Callister-v3 October 4, 2007 11:56

2nd Revised Pages

10.12 Development of Microstructure in Eutectic Alloys • 367

0

(Pb)

Temperature (

°F)

20 60 80 100

(Sn)

+ L

j

z

z





+ L

L

 L







+

l 

m

k

L (61.9 wt % Sn)

(18.3

wt % Sn)

Composition (wt % Sn)

C 4

(40)

(97.8 wt % Sn)

Temperature (

°C)

100

200

300

200

100

0

300

400

500

600

L

(C 4 wt % Sn)

Eutectic

structure

Primary

(18.3 wt % Sn)



Eutectic

(18.3 wt % Sn)



Figure 10.16 Schematic representations of the equilibrium microstructures for a lead–tin

alloy of compositionC 4 as it is cooled from the liquid-phase region.

Figure 10.17 Photomicrograph

showing the microstructure of a

lead–tin alloy of composition 50 wt%

Sn–50 wt% Pb. This microstructure is

composed of a primary lead-richα

phase (large dark regions) within a

lamellar eutectic structure consisting

of a tin-richβphase (light layers) and

a lead-richαphase (dark layers).

400 ×. (Reproduced with permission

fromMetals Handbook,9th edition,

Vol. 9,Metallography and

Microstructures,American Society for

Metals, Materials Park, OH, 1985.)