Kinetics modeling of austenite decomposition for an end-quenched 1045 steel

Finite element simulations that predict the microstructure and properties of heat-treated steels can be significantly improved by incorporating appropriate models for the kinetics of various austenite transformations. In the present study the austenite decomposition kinetics for a 1045 steel was modeled using a modification of the transformation equation proposed by Li et al. [1]. The kinetics of the continuous cooling transformation were determined directly from an isothermal transformation diagram. To verify the predictions of the model, an end-quench test was used because it produces a wide range of microstructures. The microstructures predicted by the kinetics model for the end-quenched sample were confirmed by quantification of the microstructures observed in the end-quench experiments. Furthermore, the predicted hardness profile was in good agreement with the experimentally measured hardness profile. The kinetics model developed in the present study was compared to the models proposed by Kirkaldy and Venugopalan [2] and the unmodified model by Li. The present model provides a more accurate prediction. A microstructural-based hardness equation from the literature was also evaluated and it predicted hardness values that were above the experimentally measured values. The model we propose predicts the experimental hardness profile more accurately, since it is based on the calculated microstructure and experimental hardness values of martensite, bainite, and ferrite/pearlite.