1 Explain the microstructural changes that take place when a

1. Explain the microstructural changes that take place when an alloy having a composition of 15wt% Sn-85 wt% Pb is cooled slowly from 330°C to 130°C. [10 marks

Solution

Furthermore, the compositions of the phases,

as determined from the tie line are

C = 16 wt% Sn-84 wt% Pb

C = 97 wt% Sn-3 wt% Pb

Inasmuch as the composition of the alloy

C0 = 15 wt% Sn, application of the appropriate lever rule expressions (for compositions in weight percent tin) leads to

W = C C0 / C C = 97 15/ 97 16 = 1.01

W = C0 C/ C C = 15 16 /97 16 = 0.012