(Solved): Using the isothermal transformation diagram for a \( 1.13 \mathrm{wt} . \% \mathrm{C} \) steel allo ...

Using the isothermal transformation diagram for a \( 1.13 \mathrm{wt} . \% \mathrm{C} \) steel alloy given below, 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 treatment. In each case assume that the specimen begins \( 920^{\circ} \mathrm{C} \) and that is has been held at this temperature long enough to have achieved a complete and homogenous austenite structure. (a) Rapidly cool to \( 250^{\circ} \mathrm{C} \), hold for \( 10^{3} \) seconds, then quenched to room temperature. (b) Rapidly cool to \( 775^{\circ} \mathrm{C} \), hold for 500 seconds, then quenched to room temperature. (c) Rapidly cool to \( 400^{\circ} \mathrm{C} \), hold for 500 seconds, then quenched to room temperature. (d) Rapidly cool to \( 700^{\circ} \mathrm{C} \), hold for \( 10^{5} \) seconds, then quench to room temperature. (e) Rapidly cool to \( 650^{\circ} \mathrm{C} \), hold for 3 seconds, rapidly cool to \( 400^{\circ} \mathrm{C} \), hold for 25 seconds, then quenched to room temperature. (f) Rapidly cool to \( 350^{\circ} \mathrm{C} \), hold for 300 seconds, then quench to room temperature. (g) Rapidly cool to \( 675^{\circ} \mathrm{C} \), hold for 7 seconds, then quench to room temperature. (h) Rapidly cool to \( 600^{\circ} \mathrm{C} \), hold for 7 seconds, rapidly cool to \( 450^{\circ} \mathrm{C} \), hold for 4 seconds, then quench to room temperature.