Using the isothermal transformation diagram for a 0.45 wt% C steel alloy (Figure 10.40), determine the final microstructure (in terms of just the microconstituents present) AND approximate percentages of the microconstituents that form in 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 10^3 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 700°C (1290°F), hold at this temperature for 10^5 s, then quench to room temperature. (d) Rapidly cool to 400°C (750°F), hold for 500 s, then quench to room temperature.
Using the isothermal transformation diagram for a 0.45 wt% C steel alloy (Figure 10.40),
determine the final microstructure (in terms of just the microconstituents present) AND
approximate percentages of the microconstituents that form in 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 10^3 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 700°C (1290°F), hold at this temperature for 10^5 s, then quench to room
temperature.
(d) Rapidly cool to 400°C (750°F), hold for 500 s, then quench to room temperature.
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