Composition (at% Pb) 0 10 20 30 40 70 100 700 L 1 1200 600 L + +L MgPb M 1000 500 800 400 Temperature (C) L Temperature (F) L Mgo 600 300 200 1 400 + Mg Pb 100 B+ Mg Pb 200 Mg- 20 40 60 80 100 (Mg) Composition (wi% Pb) (Pb) (1) (12 pts) For an alloy at 200 C with an overall composition of 90 wt% Pb: (a) what are the phases present? (6) what are their compositions? (c) what are the mass fractions of each phase? (2) (4 pts) For an alloy that has 20 wt% Pb, if cool it down slowly from 700 C to 200 C, describe (draw) the microstructure at 200 C with proper labels