Question

Using the isothermal transformation diagram for a 0.45 wt% Csteel alloy (Figure below, from Callister &Rethwisch), determine the final microstructure (in terms of just the micreconstituents present) of a small specimen that has been subjected to the following time-temperature treatments. In each case assume that the specimen begins at 845°C (1550°F), and that it has been held at this temperature long enough to have achieved a complete and homogeneous austenitic structure. (a) Rapidly cool to 450°C (840°F), hold for 10 s, then quench to room temperature. (b) Rapidly cool to 625°C (1155°F), hold for 1 s, then quench to room temperature. (c) Rapidly cool to 625°C (1155°F), hold at this temperature for 10 s, rapidly cool to 400°C (750°F), hold at this temperature for 5 s, then quench to room temperature 1600 Temperature (C) .B Temperature (F) - 50% M start) 1 TTTTTTT 1 1 11 1 1 1 L M (50%) 1 11 1 1 M (90% ---- 1 1 1 1 1 0.1 1 1 0 102 103 104 105 Time is

Answer 1

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