Answer the following questions by referring to the Cu-Al phase diagram shown below.

(a) What is the lowest temperature at which a liquid can be found in a system of any composition of Cu-Al ?

(b) A common alloy composition used in airplanes is 4 at. % Cu - 96 at. % Al. For this overall system composition, identify what phases are present at 500 degrees C. Select all phases present:
Liquid
Vapor
Al
Cu
CuAl2
CuAl
Cu1.5Al
Cu9Al4
Cu4Al
Cu0.75Al0.25

(c) What phases are present at a 50/50 mixture of Al/Cu at 660 degrees C? Select all phases present:
Liquid
Vapor
Al
Cu
CuAl2
CuAl
Cu1.5Al
Cu9Al4
Cu4Al
Cu0.75Al0.25

(d) In the previous question, you should have identified two phases. What is the phase fraction of the first phase you identified?