Question 10.9: Solidification of a Cu-40% Ni Alloy Determine the amount of ......
Solidification of a Cu-40% Ni Alloy
Determine the amount of each phase in the Cu-40% Ni alloy shown in Figure 10-11 at 1300 °C, 1270 °C, 1250 °C, and 1200 °C.
● 1300 °C: There is only one phase, so 100% L.
● 1270 °C: % L = \frac{ 50 \ – \ 40}{50 \ – \ 37} × 100 = 77%
% α = \frac{ 40 \ – \ 37}{50 \ – \ 37} × 100 = 23%
● 1250 °C: % L = \frac{ 45 \ – \ 40}{45 \ – \ 32} × 100 = 38%
% α = \frac{ 40 \ – \ 32}{45 \ – \ 32} × 100 = 62%
● 1200 °C: There is only one phase, so 100% α.
Note that at each temperature, we can determine the composition of the phases in equilibrium from the ends of the tie line drawn at that temperature.
This may seem a little odd at first. How does the α phase change its composition? The liquid phase also changes its composition, and the amounts of each phase change with temperature as the alloy cools from the liquidus to the solidus.