Question

A 1.5-kg specimen of a 88 wt% Pb-12 wt% Sn alloy (Animated Figure 9.8) is heated to 220°C; at this temperature it is entirely an α-phase solid solution. The alloy is to be melted to the extent that 50% of the specimen is liquid, the remainder being the α phase. This may be accomplished either by heating the alloy or changing its composition while holding the temperature constant. (a) To what temperature must the specimen be heated? °C [The tolerance is +/-290.] (b) How much tin must be added to the 1.5-kg speci220°C to achieve this state? kg [The tolerance is +/-10%.]

Answer 1

Composition (at% Sn) 100 80 60 20 40 0 327°C 600 300 Liquid 500 232°C 400 200 183°C 97.8 61.9 18.3 300 100 α+ 200 100 0 80 100 40 60 20 (Sn) Composition (wt% Sn) (Pb)

b-12- atov d'aaPo inga bove deagrom a a Soid pheu rege roduu e A t220 By addi 2 erCo be new aloy compaitteen C- Co L-CA 4-6 X160 = 3L