Using the isothermal transformation diagram for an iron-carbon alloy of eutectoid composition below. specify the nature of the final microstructure in terms of microconstituents present and approximate percentages (show your supporting work). In each case, the specimen begins at 760 C (1400 F) and has been held long enough to achieve austenitic structure. (a) Rapidly cool to 250 C (480 F), hold for 100 s, and quench to room temperature. (b) Rapidly cool to 350 C (660 "F), hold for 10" s, and quench to room temperature. Temperature (C) 800 700 500 500 400 300 200 100 T T 10-1 A 0-x-4- M(start) M(50%) M(90%) 10 -Eutectoid temperature M+A P ----3-1 B 10 Time (e) 50% 10 104 1400 1200 1000 800 600 400 200 105 Temperature (F)