Question

HW Module 10 Due: March 31, 2019 11:59PM 1- Using the isothermal transformation diagram for an iron-carbon alloy of eutectoid composition (Following Figure), specify the nature of the final microstructure (in terms of micro constituents present and approximate percentages of each) of a small specimen that has been subjected to the following time-temperature treatments. In each case assume that the specimen begins at 760°C (1400°F) and that it has been held at this temperature long enough to have achieved a complete and homogeneous austenitic structure. a) Cool rapidly to 350°C (660°F), hold for 1000 s, then quench to room b) Rapidly cool to 625°C (1160°F), hold for 10 s, then quench to roonm c) Rapidly cool to 600°C (1110°F), hold for 4 s, rapidly cool to 450°C (840°F), temperature. temperature. hold forl0 s then quench to room temperature. d) Reheat the specimen in part (c) to 700°C for 20h. c) Cool rapidly to 665°c (1230°F), hold for 1000 s, then slowly to room f) Rapidly cool to 575°C (1065°F), hold for 20 s, rapidly cool to 350°c (660°F), g) Rapidly cool to 350°C (660°F), hold for 150 s, then quench to room temperature hold for 100 s, then quench to room temperature. temperature Eutectoid temperature 1400 700 1200 600 1000 400 800 2 600 M(start) M(50%) M(90%) 200 50% M + A 400 100 200 10-1 1 10 102 103 104 105 Time (s)

Answer 1

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