2. A graphite crucible was held at 1100°C for students to do alloying experiments. Initially,1000 g of a Zn-Cu alloy with the wt10% Cu was completely melted in the crucible.

The students poured another molten Zn-Cu alloy with 20 wt%Cu into the crucible at a constant rate of 20 g/s. The added molten alloy was mixed uniformly with the existing alloy in the crucible instantly under vigorous stirring. At the same time, the mixed alloy was draining at a constant rate of 10 g/s from the bottom of the crucible. Assuming there is no oxidation or material loss due to evaporation, after 100 s, the experiment on the alloy adding/draining was stopped, and the crucible was cooled down slowly to room temperature. (a) What is the final composition of the alloy in the crucible? (b) During the cooling of the alloy in the crucible, what phase transition will happen? (c) Schematically draw the microstructure of the alloy when the temperature is at 650°C.