A 2.0-kg specimen of an 85 wt% Pb-15 wt% Sn alloy is heated to 200°C (390°F); at this temperature it is entirely an α-phase solid solution (Figure 9.8). 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 by heating the alloy or changing its composition while holding the temperature constant.
(a) To what temperature must the specimen be heated?
(b) How much tin must be added to the 2.0-kg specimen at 200°C to achieve this state?