Method for Predicting the Microstructure of Steels Quenched Isothermally at a Temperature Below M_s

An improved method is suggested for predicting the fractions of microstructure constituents formed in alloy steels during austempering and one-step quenching-partitioning in the temperature range of martensitic transformation. The temperature dependence of exponent n of the Austin–Rickett equation modeling the kinetics of isothermal bainitic transformation at a temperature below M_s is obtained using dilatometric studies of a number of steels. The developed method also allows for the equilibrium condition of the α- and γ-phases, which characterizes suspension of the bainitic transformation during isothermal holding, as well as the inevitable formation of carbides. The method enhances the adequacy of prediction as compared to the traditional methodology.