a) A diffusion couple is formed by joining a thick piece of pure copper to a thick piece of 70%Cu and 30%Zn alloy. All compositions in the Cu-Zn system below 35%Zn are FCC solid solution. i. Sketch a possible C(x) plot for this system before and after a diffusion anneal. [3 marks] ii. Which way would the makers initially on the joint move with time? [3 marks] iii. If some of the excess vacancies precipitate as voids, which side of the joint would they form? Motivate your answer fully in (i) and (ii). [6 marks] b) A diffusion couple (including inert wires) is made from pure copper and bronze with composition 80Cu20Sn. After 50 days, it is determined that the markers had moved a distance of 0.125mm. Microanalysis shows that the composition at the markers is XSn =0.12 and XCu=0.88 and that the concentration gradient dXSn/dx is 0.082mm1. By analysing the complete penetration curve, the interdiffusion coefficient at the markers is calculated as 4.01013m2/s. Calculate the intrinsic diffusion coefficients of Cu and Sn in bronze containing 12 atomic %Sn. [8 marks] c) The diffusion coefficients for copper in aluminum at 500C and 600C are 4.81014 and 5.31013m2/s, respectively. Determine the approximate time at 500C that will produce the same diffusion result (in terms of concentration of Cu at some specific point in Al ) as a 10 -h heat treatment at 600C. [3 marks] d) A heat treatment company carburizes components for the use in the mining industry using a gas furnace. In one of the components the carbon content was determined as 0.3% Carbon. In order to achieve a good wear resistance property, it is required that the component must have a carbon content of 0.45%C at a depth of 0.6mm. This component is carburized at 1060.3C for 4 hours. Calculate the carbon concentration of the carburizing gas to be used to achieve the required results. [5 marks| e) At approximately what temperature in C would a specimen of -iron have to be carburized for 4h to produce the same diffusion result as carburization at 1000C for 12h ? [8 marks|