Materials Engineering Assignment Questions and Tasks

Question 1

a) Draw a three-dimensional schematic of the simple fcc and bcc unit cells. Which of these is adopted by the matrix of your allocated alloy? Sketch and label the (211) and (301) planes on your unit cells (or a fresh drawing, if you prefer).

b) Compare and contrast the unit cell of your alloy’s matrix phase with that of the pure element on which your alloy is based.

c) In comparison with the pure element on which your alloy is based, what effect does the composition of your alloy have on the movement of dislocations in the matrix grains when a large stress is applied at room temperature?

d) Explain to what extent knowledge of your alloy’s crystal structure can be used to estimate the likely ductility of your alloy.

Question 2

a) Using your three allocated materials construct a table that provides data for their respective (i) Young’s modulus, (ii) density, (iii) thermal conductivity, and (iv) strength. You should make your sources clear by using full bibliographic references and state any assumptions you have made.

b) With reference to your data for Young’s modulus, explain qualitatively the differences in the tensile stiffness of your three materials.

c) How does your allocated alloy’s density compare with the range of density exhibited by (i) the spectrum of common engineering alloys, and (ii) all engineering material classes? Account for your alloy’s density relative to other materials.

d) With reference to your data for thermal conductivity, explain qualitatively the difference between the values for your three materials.
2 marks

e) Draw schematic tensile stress-strain curves for all three of your materials and use these to compare and contrast their elastic response, plastic response, and the nature of their fracture.

Question 3

Using data for Young’s modulus, linear coefficient of thermal expansion, and tensile strength, compare and contrast the estimated thermal shock resistance of your ceramic with that of both soda glass and borosilicate glass.

Describe the role that thermal conductivity can play in thermal shock resistance.

Question 4

Technical ceramics are often processed from a fine powder precursor. Various methods that create a green body, followed by the application of heat and/or pressure for consolidation, are used commercially.

a) Describe such a process for your allocated ceramic. Your answer should include the necessary steps from loose powder to final product, as well as key details such as temperatures, dwell times, etc. 2 marks

b) Carefully consider the role of Young’s modulus, thermal conductivity, and failure stress on the specific details of the process used to manufacture your allocated ceramic. 4 marks

c) How difficult is it to make your ceramic 100% dense? Why is this the case? 4 marks

Question 5

Your allocated polymer can be processed in a number of ways. Many of these will cause alignment of the polymer chains.

a) With clear reference to the concept of processing-structure-property relationships explain how processing might be expected to affect: (i) the crystallinity, (ii) the volume fraction of amorphous regions, and (iii) the anisotropy of tensile properties. 4 marks

b) Compile a list of common additives which can be included in your material. Provide details of the mechanism/s that enable one of these additives to achieve its purpose. 2 marks

c) Compare and contrast the recyclability of your allocated polymer with the wider family of polymers

d) What implications does your material’s Tg have on its behaviour from –100?C to +100?C? 2 marks

Question 6

a) Explain the microstructural changes that your allocated alloy exhibits during age hardening. You should use a sketch the microstructure of your material (i) held for 30 minutes at the solution temperature, (ii) after, subsequently, cooling rapidly from the solution temperature to room temperature, (iii) after, subsequently, holding at the commercial aging temperature for the prescribed time, to support your explanation. 4 marks

b) Compare and contrast how precipitates (i) increase the yield strength of some alloys at room temperature, and (ii) lower the creep rate of some alloys at elevated temperature. 4 marks

c) Your allocated alloy is strengthened by intermetallic precipitates that grow during aging. By both defining an intermetallic and detailing those found in your alloy, explain why they are so effective at strengthening your material. 2 marks

Question 7

a) In the course of your studies in this module we have adopted implicitly a specific definition of a hybrid material. By describing that definition make a case for how an engineering material might be distinguished from a structure. 5 marks

b) Explore the potential for combining any of your three materials as pairs to form a useful hybrid engineering material.