Cellular automaton simulation of microstructure evolution during austenite decomposition under continuous cooling conditions

A two-dimensional diffusion based model is developed to describe transformation of austenite into ferrite and pearlite under continuous cooling conditions. The nucleation of ferrite is assumed to occur over grain boundaries and the nucleation of pearlite is assumed to be taking place all over the grain and at growing ferrite-austenite interfaces, when the composition and temperature conditions are favourable. A cellular automaton algorithm, with transformation rules based on this model is used for the growth of ferrite and pearlite. Model predicted results for continuous cooling transformations are verified by comparing the model predicted microstructure features with the experimental measurements for two sets of plain carbon steels of different composition and austenite grain size. Using the model, it is possible to generate results like under-cooling to start ferrite and pearlite transformations, which are difficult to obtain experimentally.