Computer simulation of TTT diagrams of some hypoeutectoid plain carbon steels

The experimental determination of TTT diagrams is expensive and tedious. As an alternative to this, computer simulation models are developed. A diffusion based two dimensional model is developed to describe the isothermal decomposition of austenite into ferrite and pearlite. The nucleation of ferrite is assumed to occur over austenite grain boundaries and that of pearlite is assumed to take place all over the grain and at the growing ferrite-austenite interfaces, when the composition and incubation time conditions are favourable. A cellular automaton algorithm, with transformation rules based on this model is used for the growth of ferrite and pearlite. The model based results for isothermal transformations are verified by comparing the predicted transformation start and end times with the corresponding experimental values available for similar steels.