1. Using the TTT diagram for an iron-carbon alloy of eutectoid composition as shown in the figure below, 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 800°C and that it has been held at this temperature long enough to have achieved a complete and homogeneous austenitic structure. If pearlite forms, please specify whether it is coarse or fine pearlite. Temperature (°C) 800 700 A 600 500 400 300 A(Austenite) M(start) (Martensite) 200 M(50%) M(90%) 100- ΟΙ 10-1 1400 Eutectoid temperature 1200 P (Pearlite) 1000 B(Bainite) 800 600 50% 400 M+A 10 102 103 104 105 Time (s) 200 Temperature (°F) (a) Cool rapidly to 675°C, hold for 10 s, then quench to room temperature. (b) Cool rapidly to 400°C, hold for 2 s, then quench to room temperature. (c) Cool rapidly to 450°C, hold for 200 s, then quench to room temperature. (d) Rapidly cool to 575°C, hold for 20 s, rapidly cool to 350°C, hold for 100 s, then quench to room temperature (e) Rapidly cool to 250°C, hold for 100 s, then quench to room temperature in water. Reheat to 315°C for 1 h and slowly cool to room temperature.