A copper–nickel alloy of composition 70 wt% Ni–30 wt% Cu isslowly heated from a temperature of 1300C (2370F).(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?
Question
A copper–nickel alloy of composition 70 wt% Ni–30 wt% Cu isslowly heated from a temperature of 1300C (2370F).(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?
Solution
To answer these questions, we need to refer to the phase diagram of the copper-nickel alloy system.
(a) The first liquid phase forms at the temperature where the liquidus line intersects the composition line of 70 wt% Ni–30 wt% Cu. This is typically around 1300°C.
(b) The composition of the first liquid phase is determined by drawing a tie line at the temperature where the first liquid forms and reading off the composition at the intersection with the liquidus line. This will be slightly richer in Ni than the overall composition.
(c) Complete melting of the alloy occurs at the temperature where the solidus line intersects the composition line of 70 wt% Ni–30 wt% Cu. This is typically slightly higher than the temperature where the first liquid forms, around 1350°C.
(d) The composition of the last solid remaining prior to complete melting is determined by drawing a tie line at the temperature where complete melting occurs and reading off the composition at the intersection with the solidus line. This will be slightly richer in Cu than the overall composition.
Please note that the exact temperatures and compositions can vary slightly depending on the specific phase diagram used.
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