Metals A and B of melting points 700 and 920^oC, respectively, are mutually soluble in the liquid state but only partially soluble in the solid state. At 400⁰C the solubility of B in A is 14 wt%, and the solubility of A in B is 9 wt%; at room temperature the solubilities are 1 wt% and 0.1 wt%, respectively. Thermal analysis (from cooling curves) yields the following data:

Alloy Composition              Liquidus                Solidus

wt% B                                    temp in oC             temp in oC

10                                           640                         500

20                                           572                         400

40                                           435                         400

50                                           450                         400

70                                           660                         400

90                                           840                         400

95                                           880                         650

a) Using the above data, use graph paper to construct a phase diagram. Label all phase regions, lines, and points. (Hint: remember to use the solubility data, too; Hint: think about how the curves will extrapolate, because your data is incomplete).

b) Estimate the eutectic composition (in wt%B). What are the compositions of the phases in the eutectic, just below the eutectic temperature?

c) Sketch the microstructures which form during slow cooling of an alloy containing 25%B from its liquid state to room temperature.

d) Sketch final microstructures for alloys of composition 5%B, the eutectic composition, and 60%B.