Modeling of Ferrite-Austenite Phase Transformation

A two-dimensional cellular automaton model is adopted to simulate the ferrite (α)-austenite (γ) transformation in low-carbon steels. The preferential nucleation sites of austenite, the driving force of phase transformation, carbon redistribution at α/γ interfaces, and carbon diffusion in both the α and γ phases are considered. The model is applied to simulate the phase transformation and carbon diffusion during heating at 815°C, and subsequent cooling at 5°C/s to room temperature and tempering at 300°C-500°C. The process of heating at 600°C after cooling from 815°C, but prior to cooling to room temperature, is also simulated to compare to the tempering process. The results show that during the isothermal heating at 815°C, the carbon distribution becomes uniform gradually in both the α and γ phases. The subsequent cooling to room temperature at 5°C/s results in a non-uniform carbon distribution, while the uniformity increases with tempering temperature. During the 600°C heating, the carbon distribution is uniform within 1 min. The simulation results are used to understand the processing-microstructure-property relationships of an enameling steel.