2- Using the following TTT diagram, identify microstructure that would achieve after each of the following heat treatment. In each case assume that the heat treatment begins at 760°C, with a fully austenitic structure. Rapid cooling represents cooling in less than a second a. Rapidly cool to 350°C, hold for 104 s, and quench to room temperature b. Rapidly cool to 250°C, hold for 100 s, and quench to room temperature c. Rapidly cool to 650°C, hold for 10 s, then rapidly cool to 400°C, hold for 1000 s, and quench to room temperature d. Which of the above heat treatment leads to the highest strength in the material? Temperature (°C) 800 700 600 A 500 400 A 300 A P Eutectoid temperature 1400 B T 1200 1000 800 600 M(start) 200 50% M(50%) M+A 400 M(90%) 100 0 10-1 1 10 10 102 103 104 105 Time (s) 200 Temperature (°F)