A copper-nickel alloy of composition 60 wt% Ni-40 wt% Cu is slowly heated from a temperature of 1250°C (2280 °F). (a) At what temperature does the first liquid phase form? (b) What is the composition of this liquid phase? (c) At what temperature does complete melting of the alloy occur? (d) What is the composition of the last solid remaining prior to complete melting?

a. The very first liquid process, when heated from 1250 degree Celsius, is expected to form at the temperature by which the vertical line crosses the phase boundary (a - (a + L)) which is about 1310 degree Celsius.

b. The structure of that first liquid is identified by the intersection with ((a + L) - L) phase boundary; 47wt %of Ni is of a tie line formed across the (a + L) phase area at 1310 degrees.

c. To find the alloy's full melting, it is determined that the intersection of the same vertical line at 60 wt percent Ni with (a - (a+L)) phase boundary is around 1350 degrees.

c. The structure of the last remaining solid before full melting correlates to the intersection with the phase boundary (a - (a + L), of the tie line built at 1350 degrees across the (a + L) phase area, being 72wt % of Ni.