The key to strengthening in metals is in hindering dislocation motion, list the four main ways in which this can be achieved, giving brief descriptions of why dislocation motion is hindered in each case. (10 marks)
(ii) In one of the four strengthening cases above, identify another mechanical property that is significantly degraded, and explain why this has occurred even though strength is increased. (4 marks)
(iii) Discuss to how these strengthening mechanisms will affect high temperature failure processes such as creep. How would metals be engineered to be resistant to creep and high temperature fatigue failure? What are the key factors to consider when selecting a metallic system for high temperature application?