Materials Science II
The silver copper system has a eutectic at 71.9wt% silver. At the eutectic
temperature (780°C) 7.9wt% silver
dissolves in copper and 8.8wt% copper dissolves in silver whereas at room
temperature the solubilities are 2.2wt% and 1.2wt% respectively. The melting
points of pure copper and silver are 1080°
C and 950° C respectively. Sketch the phase
Mark on the phase diagram from question 1 the lines corresponding to liquidus,
solidus and solvus.
An alloy containing 30% silver and 70% copper is slowly heated from room
temperature. Describe the microstructural changes which occur answering the
(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
What is meant by a eutectic reaction? Is it described by a line, a point
or an area on the phase diagram?
A 50wt%Ni-50wt% copper alloy is slowly cooled from
1400° C. Describe the development of
microstructure on cooling answering the following questions.
(a) At what temperature does the first solid phase form?
(b) What is the composition of this solid phase?
(c) What are the proportions of solid and liquid at
For a lead-tin alloy of composition 80wt% Sn-20wt% Pb and at
180° C determine the following:-
(a) The mass fractions of the
(b) The mass fractions of primary
b and eutectic
(c) The mass fraction of b
in the eutectic mixture.
[All the necessary phase diagrams are on HO2]