Materials Science Forum, Vol.426-4, 1405-1412, 2003
Modelling upper and lower bainite trasformation in steels.
Bainite microstructure is of considerable importance in the design of high strength steels. There are two types of morphologies, upper and lower bainite. In upper bainite, cementite forms between two adjacent bainitic ferrite grains. In some cases, cementite does not form but stabilized austenite instead remains with bainitic ferrite. In lower bainite, cementite precipitates within the grains. In order to model the development of both upper and lower bainite microstructures, it is necessary to simulate the formations of bainitic ferrite and cementite simultaneously. In the present work, new model for the simultaneous reactions, consisting of bainitic ferrite precipitation from austenite and cementite precipitation in both austenite and bainitic ferrite, has been established. Volume fractions of each phase, cementite particle size and transition between upper and lower bainite can be predicted. Some experimental data have also been obtained and compared with calculations.