Question

Q7 Nichrome materials are alloys consisting of Nickel and Chromium. They are widely used for resistant heating wires in applications like toasters, space heaters or hair dryers. Answer the following

questions about the Ni-Cr phase-diagram shown below. Express all compositions as Cr-x wt.% Ni, e.g. the eutectic composition (which is explicitly shown in this particular diagram) would be written as Cr-49 wt.% Ni. a) Label all regions on the phase diagram with their corresponding phases, using the following labels: \begin{array}{l} \mathrm{L} \\ \alpha(\mathrm{Cr}) \\ \beta(\mathrm{Ni}) \\ \mathrm{Ni}_{2} \mathrm{Cr} \end{array} b) Consider a composition of Cr-22 wt.% Ni. What is the chemical composition (in wt.%) of the very first solid to appear in a liquid alloy of this overall composition that is cooled slowly from 1800°C.? (2 mark) c) At what temperature does this solid begin to form in the liquid? (1 mark) d) For the same composition alloy: (3 marks) e) For the same alloy: (3 marks) I.What are the compositions (in wt.%) of the two phases present at 1600°C? II.What are the relative fractions of the two phases that are present at 1600°C? I.What are the compositions (in wt.%) of the two phases present at 900°C? II.What are the relative fractions of the two phases that are present at 900°C? f) What is the lowest temperature a fully liquid Cr-Ni alloy can exist at and what is the composition of that liquid? (1 mark)

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