Temperature, "C Temperature (C) 800 700 600 A 500 400 A 300 A Eutectoid temperature 1400 P 1200 1000 B 800 600 M(start) 50% 200 M+A 400 M(50%) M(90%) 100 10-1 1 10 102 103 104 105 Time (s) 800 70 700 600 500 400 300 Ms TTT Diagram -Eutectoid temperature 200 Continuous cooling transformation curves Normalizing Full anneal Oil quench Critical cooling rate Isothermal transformation curves Water quench! 200 100 -Mo Martensite Martensite and pearlite Fine pearlite Coarse pearlite 0 0.1 1 10 100 10 10+ 105 Time, in seconds CCT Diagram Temperature (F) Using the TTT diagram and the CCT diagram provided, answer the following: a) For a steel held initially at 1000 C consider the following cooling schemes and name the resulting microstructure(s) (3 marks) i. Quenched to 125C b) ii. Quenched to 600C, held for 20 minutes, and then quenched to 100 C The bainite region on the TTT diagram can be further subdivided into upper and lower bainite. Describe each and explain the driving forces responsible for creating one over the other. (4 marks) c) A steel is cooled continuously as presented in the table below. What is the name of the possible quenching process? What is the microstructure of the final steel product? Explain. (3 marks) Temperature (C) Time (Seconds) 750 600 0.1 1 400 100 10 100