Using the isothermal transformation diagram for a 0.45 wt% C steel alloy (Figure 10.39), determine the final microstructure (in terms of just the micro constituents 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 250°C (480°F), hold for 103 s, then quench to room temperature.
(b) Rapidly cool to 700°C (1290°F), hold for 30 s, then quench to room temperature.
(c) Rapidly cool to 400°C (750°F), hold for 500 s, then quench to room temperature.
(d) Rapidly cool to 700°C (1290°F), hold at this temperature for 105 s, then quench to room temperature.
(e) Rapidly cool to 650°C (1200°F), hold at this temperature for 3 s, rapidly cool to 400°C (750°F), hold for 10 s, then quench to room temperature.
(f) Rapidly cool to 450°C (840°F), hold for 10 s, then quench to room temperature.
(g) Rapidly cool to 625°C (1155°F), hold for 1 s, then quench to room temperature.
(h) 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.