3. Consider a carbon steel alloy containing 1.15 wt% C, cooled to below 727C (1341F). (a) What is the proeutectoid phase can be retained at room temperature? (b) Compute the mass fractions of a-ferrite and cementite in pearlite. c) Compute the mass fractions of pearlite and the proeutectoid phase form? (d) Schematically sketch and label the resulting microstructure. Composition Cat%C) 10 15 20 1600 1538-C 1493 0 L 1400 2500 13940 Y 1200 11470 7. Austenite 2.14 4.30 1 2000 Temperature ("C) 1000 Temperature (F) 912 C y Feyc 800 1500 7270 0.76 0.022 600 a, Ferrite Fezc Cementite (Fe,c) 1000 400 0 (Fe) 6 6.70 3 Composition (wt% )