Competition between nucleation and early growth of ferrite from austenite - Studies using cellular automaton simulations

A model for the nucleation of ferrite on austenite grain boundaries and the growth of these nuclei along the grain boundary and into the grain, is dev eloped. A cellular automaton algorithm, with transformation rules based on this model, is used to simulate the decomposition of austenite into ferrite . When performed under continuous cooling conditions, the simulations give an insight into the competition between nucleation and early growth, which determines the variation of ferrite grain size with the cooling rate and wi th austenite grain size. The number of ferrite grains per austenite grain, ferrite grain size and the kinetics of ferrite formation are obtained as a function of the cooling rate and austenite grain size. Contour plots of the volume fraction of ferrite in the cells at different times, enables visual ization of the ferrite growth process. (C) 1998 Acta Metallurgica Inc. Publ ished by Elsevier Science Ltd. All rights reserved.