7. (40 pts) EXTRA CREDIT EXTRA CREDIT EXTRA CREDIT A magnesium-lead alloy of mass 7.5 kg consists of a solid alpha phase which has a composition that is exactly at the solubility limit for Pb in Mg at 300°C (570°F) (10 pts) (10 pts) (a) (b) What mass of lead is in the alloy? If the alloy is heated to 400°C (750°F), how much more lead may be dissolved in the alpha phase without exceeding the solubility limit of this phase? The magnesium-lead phase diagram. (Adapted from Metals Handbook: Metallography, Structures and Phase Diagrams, Vol. 8, 8 edition, ASM Handbook Committee, T. Lyman, Editor, American Society for Metals, 1973, p.315.) temperature C 100 M 600- 500- 400 200- Composition (ar% Pol 10 70 100 L 1200 Composition (wt% P 60 80 100 2 1000 800 600 400 Temperature)