Modeling austenite decomposition into ferrite at different cooling rate in low-carbon steel with cellular automaton method

Abstract

The austenite decomposition into ferrite during continuous cooling in low-carbon steel has been investigated with a two-dimensional cellular automaton (CA) approach. In this model, the growth of ferrite grain is controlled by both carbon diffusion and γ– α interface dynamics. In order to predict the growth kinetics of ferrite grain, the coupled carbon diffusion behavior in untransformed austenite and γ– α interface dynamics are numerically resolved. The simulation provides an insight into the carbon diffusion process in retained austenite and microstructure evolution during the transformation. The predicted ferrite growth kinetics and average grain size at different cooling rates are compared with experimental results in the literature and the simulated results show that the final grain size and newly formed ferrite fraction vary with cooling rate. The γ– α interface is stable in the studied cooling rate range (up to 58 °C s −1) in this work, so the simulated morphology of ferrite grain is almost equiaxed, which is not influenced by the anisotropy of the hexagonal mesh in this CA model.