A Thermodynamic-Based Model to Predict the Fraction of Martensite in Steels

A thermodynamic-based model to predict the fraction of martensite in steels with undercooling has been developed. The model utilizes the thermodynamic driving force to describe the transformation curve and it is able to predict the fraction of athermal martensite at quenching to different temperatures for low alloy steels. The only model parameter is a linear function of the martensite start temperature (M (s)), and the model predicts that a steel with a higher M (s) has a lower difference between the martensite start and finish temperatures. When the present model is combined with a previously developed thermodynamic-based model for M (s), the model predictions of the full martensite transformation curve with undercooling are in close agreement with literature data.