A 30 wt% Sn-70 wt% Pb alloy is heated to a temperature within the alpha+ liquid

Question

A 30 wt% Sn-70 wt% Pb alloy is heated to a temperature within the alpha+ liquid phase region. If the mass fraction of each phase is 0.5, estimate: (a) The temperature of the alloy (b) The compositions of the two phases Please explain. I have a big test tomorrow morning. Please handwrite and write quite legibly for everyone to read. Write very legibly and neatly so that it is easy to read out and understand. Do not let the edges of a scanned or pictured image are cropped, resulting illegible scripts. Do not skip steps. Never use the multiply symbol (times) between numbers and letters. I need solutions and answers as soon as possible. Many thanks.

Explanation / Answer

ead-tin alloy of composition 30 wt% Sn-70 wt% Pb from 150°C and utilizing

The first liquid forms at the temperature at which a vertical line at this composition intersects the eutectic isotherm--i.e., at 183°C.

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The composition of this liquid phase corresponds to the intersection with the ( + L)–L phase boundary, of a tie line constructed across the + L phase region just above this eutectic isotherm--i.e., CL = 61.9 wt% Sn.

c) Complete melting of the alloy occurs at the intersection of this same vertical line at 30 wt% Sn with the ( + L)–L phase boundary--i.e., at about 260°C.

The composition of the last solid remaining prior to complete melting corresponds to the intersection with –( + L) phase boundary, of the tie line constructed across the + L phase region at 260°C--i.e., C is about 13 wt% Sn.

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