A physically based approach to model the incomplete bainitic transformation in high-Si steels

Abstract

Abstract This paper describes an approach to simulate the incomplete bainitic transformation observed in high-Si steels. The model can capture the incomplete transformation when a simple procedure accounting for carbon enrichment in the remaining austenite is applied to calculate the change in the zero transformation temperature, which is a key parameter controlling the transformation kinetics. The carbon concentration in the remaining austenite is determined by the volume fraction of bainitic ferrite and the effective carbon concentration of the bainitic ferrite. Comparison with experimental data for Fe-0.3C-2.4Mn-1.8Si is made, which demonstrates that the isothermal kinetics of bainite formation in the range 370–480°C can be satisfactorily described with the model by using a single set of model parameters and only adjusting the carbon concentration of the bainitic ferrite. A good agreement is found between predicted final carbon contents of retained austenite and those measured using X-ray diffraction, which indicates that a plausible carbon dependency of the zero transformation temperature has been assumed in the calculations.