Three types of cooling were performed as drawn on the isothe

Three types of cooling were performed as drawn on the isothermal transformation diagram (on next page) for a steel of eutectoid composition. Describe the possible microstructures and their (approximate) amount/percentage present in the steel at the end of each path. Cooling Path 1: Heat to 800 degree C and hold there for a long time then slowly cool down to 650 degree C in a period of 1000 s then quench (or rapid cool) to room temperature. The resulting micro - microconstituents: 100 % bainite 100% martensite 100% pearlite 50% pearlite, 50% martensite Cooling Path 2: Heat to 800 degree C and hold there for a long time then quench to 500 degree C hold there for 1000 s and then quench to room temperature. The resulting micro - microconstituents: 100 % bainite 100% martensite 100% pearlite 50% pearlite, 50% martensite Cooling Path 3: Heat to 800 degree C and hold there for a long time then slowly cool down to 675 degree C in a period of 100_s and then quench to room temperature. 100 % bainite 100% martensite 100% pearlite 50% pearlite, 50% martensite

Solution

b) 1

a) 3

c) 4