(Solved): Isothermal transformation diagram for a eutectoid steel is shown below. a) If a sample is quenched ...

Isothermal transformation diagram for a eutectoid steel is shown below. a) If a sample is quenched from austenite region and held at 550° C until the transformation is complete would its microstructure be i) Fine pearlite ii) Coarse pearlite or iii) Bainite? Select the correct response. Explain how the two others could be obtained by drawing time temperature cooling paths on the diagram shown. b) By cooling the another sample from the austenite region rapidly to 700° C, holding it for 10 s, then quenching to room temperature (as shown in the figure) what will be the phases (and microconstituents) present? What is the approximate percentage of each? c) Explain how you would heat treat martensite to increase its toughness without much reducing its hardness. 800 Eutectoid temperature 1400 700 1200 600 1000 500 800 Temperature ("C) 400 300- 200 100 0 10-1 A M (start) M (50%) M (90%) 10 M + A 10² Time (s) 18 50% 10? 104 1 T L 11 600 1 400 200 10? Temperature (°F)