3. 1.5-kg specimen of a 90 wt% Pb-10 wt% Sn alloy is heated to 250°C, at which temperature it is entirely an a -phase solid solution. The alloy is to be melted to the extent that about 50% of the specimen is liquid, the remainder being the L 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? (b) How much tin must be added to the 1.5-kg specimen at 250°C to achieve this state?

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