Answer/Explanation:
From the isothermal transformation diagram for a eutectoid steel, the following can be deduced
1 and 2
Cooled Instantly from 800 to 630 C and held for 10 seconds.
No transformaton and 100% austenite will be there in the microstructure specimen
3) Cooled to 400oC and held for 200 seconds
During the rapid cooling 400°C and held for 200seconds, approximately 50℅ will have transformed into coarse pearlite, and 50% of remaining 50% will have transformed into Bainite.
(4) Quenched to room temperature.
Upon quenching to room temperature, 25% of the original specimen transforms to martensite.
