Using the isothermal transformation diagram for an iron–carbon alloy of eutectoid composition, specify the nature of the final microstructure (in terms of microconstituents 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 103 s, then quench to room temperature. (b) Rapidly cool to 625∘C(1160∘F), hold for 10 s, then quench to room temperature. (c) Rapidly cool to 600∘C(1110∘F), hold for 4 s, rapidly cool to 450∘C(840∘F), hold for 10 s, then quench to room temperature. (d) Reheat the specimen in part (c) to 700∘C(1290∘F) for 20 h. (e) Rapidly cool to 300∘C(570∘F), hold for 20 s, then quench to room temperature in water. Reheat to 425∘C(800∘F) for 103 s and slowly cool to room temperature. (f) Cool rapidly to 665∘C(1230∘F), hold for 103 s, then quench to room temperature. (g) Rapidly cool to 575∘C(1065∘F), hold for 20 s, rapidly cool to 350∘C(660∘F), hold for 100 s, then quench to room temperature. (h) Rapidly cool to 350∘C(660∘F), hold for 150 s, then quench to room temperature.