Modeling of Austenite Decomposition during Continuous Cooling Process in Heat Treatment of Hypoeutectoid Steel with Cellular Automaton Method

The austenite decomposition during continuous cooling process in heat treatment of hypoeutectoid steel is studied with experimental method and numerical simulation. To investigate the phase transformation, quenching experiments are conducted and the microstructure evolution is investigated through metallographic examination. Dilatometric experiments are conducted as well and the experimental results are employed to analyze the phase transformation process during austenite decomposition. Subsequent studies of austenite decomposition in the steel are conducted using a numerical model based on cellular automaton (CA) method. In the simulation, the transformation of austenite into ferrite and pearlite is simulated, and the growth kinetics and average grain size of ferrite as well as the average interlamellar spacing of pearlite were obtained. The simulation results of the effects of cooling rate on the average grain size of ferrite and interlamellar spacing of pearlite agree well with the experimental results. Finally, integrated with a previously developed model for the austenization in heating process of heat treatment, the present model shows a capacity to investigate the effect of the prior austenite grain size on the final microstructure formed at the end of austenite decomposition.