The diagram which follows shows the TTT diagram for a coarse

The diagram which follows shows the TTT diagram for a coarse-grained, plain carbon steel of eutectoid composition. Samples of the steel are austenitized at 850 degree C and then subjected to the quenching treatments shown on the diagram. Describe the microstructure produced by each heat treatment.

Solution

The microstructure produced will be martensite and unstable austenite. This is because quenching will bring the temperature to near about room temperature i.e. 10-25 degree celsius in very small fraction of time.

The martensite formation begins at 250-degree celsius and complete martensite is formed at -50 degree celsius.