Composition = 0 wt% Pb Composition = 0 at% Pb Temperature = 0 C Composition (at% Pb) Temperature = 32 C 5 10 20 30 40 70 100 700 L 1200 600 L + Mg2Pb M a+L 1000 500 800 400 Temperature (C) L + Mg2Pb B + L 300 600 200 B 400 a + Mg2Pb 100 B+ MgoPb 200 Mg2Pb 0 100 (Mg) Composition (wt% Pb) (Pb) A magnesium-lead alloy of composition 75 wt% Pb-25 wt% Mg is slowly cooled from a temperature of 600C. Using the Mg-Pb phase diagram (Animated Graph: Figure 10.20), do the following: (a) Determine the composition of the first solid phase to form. (b) Determine the composition of the last liquid remaining prior to complete solidification. (c) A schematic sketch of the microstructure at 440C is shown below. Label the phases that are present. 2 1 ULL 3 mo (a) a) i wt% Pb ) (b) i wt% Pb (c) a Primary Mg2Pb