Which of the following phase is obtained as the end product, after complete heat treatment cycle in austempering process?

Explanation

Explanation: Martensite: It is a metastable phase of steel formed by the transformation of austenite below 320°C. Martensite is an interstitial supersaturated solid solution of carbon in α – Iron and has a body-centered tetragonal lattice. It has a carbon content of up to 2% and is extremely hard and brittle . It is a product of rapid cooling (quenching) and possesses an acicular or needle-like structure. The rate of cooling and the amount of carbon percentage in steel are directly proportional to the amount of hardness achieved in martensitic transformation. Bainite: It is a plate-like microstructure that forms in steels at a temperature of 125- 550° (depending on alloy content). It forms by the decomposition of austenite at a temperature which is above MS but below that at which fine pearlite forms. Austenite: It is also known as Gamma-phase iron is a metallic, non-magnetic allotrope of iron or solid solution of iron, with an alloying element. In plain carbon steel, austenite exists above the critical eutectoid temperature of 1000 K. Austenite is of FCC crystal structure. Pearlite: It is a two-phase, lamellar structure composed of 88% ferrite and 12% cementite. Pearlite is formed when austenite cools slowly below 727°C. It is hard as well as strong because of the layered structure. It finds wide application in cutting tools, knives, high strength wire, etc.