4. Phase diagram (28 pts) A phase diagram for the solid liquid equilibrium of a binary mixture of silver (Ag) and
copper (Cu) is shown below. Answer the following questions. Note that the weight percentage is on the
bottom and the mole percentage is on the top.
Ag-Cu Silver-Copper
Atomic percentage silver
"C
1100
10
20
30
40
50
60
70
80
90
1084.5
1000
900
961.90
800
780
700
7.9
71.9
912
600
500
400
Cu
10
20
30
40
50
60
70
80
90
Ag
J.C. Chaston
Weight percentage silver
[From T Lyman et al., Metals Handbook, Metalography, Structures, and Phase Diagrams, 8th ed.
(Vol. 8) (Metals Park, OH: American Society for Metals, 1973).] Courtesy of ASM International.
Figure 1 Phase diagram of Ag-Cu Silver-Copper binary system.
a. Label silver-rich solid phase a, copper-rich solid phase b and liquid phase on the phase diagram.
(6 pts)
b. Label the Eutectic point on the phase diagram. (2 pts)
c. What is the lowest temperature at which a binary mixture can exist entirely in the liquid phase?
What is its composition? (4 pts)
d. What is the most copper that can be present in a phase of solid silver? At what temperature does
this occur? (4 pts)
e. Consider a liquid mixture of 1 mole Ag and 4 mole Cu at 800 C. At equilibrium, what phases
exist and what are their compositions? How many moles are present in each phase? (12 pts)
