Question

The following is the phase diagram for the lead-tin alloy: Pb-Sn Phase Diagram Composition (at% Sn) 100 300 500 200 83 C 61.9 97.8 300 100 100 100 Consider a lead-tin alloy containing 30 wt% Sn slowly (equilibrium) cooled from the liquid phase starting at 300°C. During this cooling process, the temperature of this alloy reaches 183.1° C (just above the eutectic temperature) and is held at this point of interest until equilibrium conditions are met. 1. (4 points) Draw a schematic of the microstructure and label the phases present: Now the alloy is slowly cooled to 182.9°C (just below the eutectic temperature) and held until equilibrium conditions are met 2. (6 points) Draw a schematic of the microstructure and label the phases and constituents

Answer 1

за 1 183 0 9 91-9 50 3 &o 30 40 60 80 loo 5rm Composition lvtt,sn) 3o f ot Sn and 7o1. t Pb is cooled -som a -tempexatuxe axound 2502, cohese the Pixst ox Phase stasts to toxm. Thus -sst

sol d phase -osm at as Co=301., CL=61.9+, Cs 18.31 CL-CO Lo-Ls C1-L5 61- 9-30 = 0.7316 61.9-18.3 30-12.3 8684 61.9-1 3 co =301 composrtion CL-CO 97 8 30 CL-L 97 8-12 3 Co-5 30-183 CL-5 7 8-18 3 18:3-0142