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This coursework is intended to assess your knowledge and understanding in relation to:
The relationship between alloy composition, microstructure and mechanical properties;;
The performance of materials in a variety of service environments.
as stated in the MPC014 Module Specification.
Questions 1 and 2 are past exam questions and question 3 will require you to conduct research
into the topic.
You may either produce your answers as an electronic document or by hand (or both). Hand_xFFFE_written documents must be legible.
Page 1 of 4 Questions continue. . .
1. (a) Explain the differences between displacive and reconstructive allotropic phase trans formations. Give an example of a microstructure produced in steels for each transfor mation type and sketch and briefly describe the microstructures.
(6 marks)
(b) For the following steels, suggest an appropriate heat-treatment that could be used
to correct the given problem. Give possible temperatures relative to A1 and/or A3,
explain what happens to the microstructure during the heat treatment and describe
the mechanisms which give rise to any changes.
i. an Fe-0.7wt%C steel quenched rapidly from 900 °C which is too brittle fo

r the
application.
(3 marks)
ii. a high-carbon steel which is very difficult to machine.
(3 marks)
iii. a forged, medium-carbon steel which has a coarse grain structure.
(3 marks)
(c) An Fe-0.7wt%C steel is slowly cooled from 900 °C. Calculate the fractions of the
transformation products when the alloy is fully cooled to room temperature.
(3 marks)
(d) If the alloy is reheated to 900 °C and fully austenitised and then quenched rapidly to
20 °C, calculate the fractions of the transformation products in the quenched alloy.
(2 marks)
Equations:
1 Vα′ = exp( 0.011(Ms Tq)) (1)
Ms(
C) = 539 (423 × weight% C) (2)
Page 2 of 4 Questions continue. . .
2. (a) You are asked to suggest an aluminium alloy for use as a car exterior body panel
produced using a stamping process. Explaining your choice, suggest a possible alloy
that could be used and give details of a final heat-treatment.
(5 marks)
(b) An Al-Li alloy is under-aged to a yield strength σu of 275 MPa. The strength can
be calculated using equation (3). If the volume fraction Vf of precipitates is 0.25,
what is the average precipitate radius r Assume the alloy strength is due only to
precipitation.
σu = 20.30G 1.5