3. The temperatures of solidus and liquidus of the silicon-germanium system are listed here. a. Draw the phase diagram and label each region. b. Is this alloy isomorphous? Explain why. c. An alloy with 50%wt is held at 1300 °C. Composition (wt% Si) Solidus Temperature Liquidus Temperature (°C) (°C) Determine the relative amounts of the two phases. 0 938 938 10 1005 1147 20 1065 1226 30 1123 1278 40 1178 1315 50 1232 1346 60 1282 1367 70 1326 1385 80 1359 1397 90 1390 1408 100 1414 1414 4. A specimen of hypoeutectoid (meaning composition is below the eutectoid) steel having a composition of 0.5% C and a mass of 1 kg is slowly cooled from a temperature 850 °C. a. If we stop cooling at a temperature just above the eutectoid isotherm, determine the fractions of the two phases and the total weight of the ferrite a phase in the specimen. This phase is called proeutectoid (meaning pre- or before eutectoid) ferrite. b. Next, the specimen is further cooled slowly to room temperature, which transforms the rest of the austenite into pearlite. Determine the total weight fraction of ferrite and the total mass of ferrite in the specimen at room temperature. c. The weight fraction of protoeutectoid ferrite (part a) is not affected by the additional cooling to room temperature. Calculate the weight fraction of the total specimen that is eutectoid ferrite at room temperature.

Fig: 1