Room temperature quenching and partitioning (RT-Q&P) processed steel with chemically heterogeneous initial microstructure

Microstructure heterogeneity has been regarded as being detrimental in obtaining reliable mechanical performance of steels. However, in the present study, we demonstrated that a proactive control of microstructure heterogeneity could deliver unprecedented tensile properties that was hardly achieved by using chemically homogeneous initial microstructure. The heterogeneity of Mn distribution generated by utilizing its solubility difference between ferrite, austenite and cementite at intercritical annealing, promoted the retention of austenite in the final microstructure subjected to the room quenching and partitioning process. The enhancement of fraction as well as the stability of austenite contributed to the simultaneous improvement of tensile strength and ductility which have been regarded as mutually exclusive properties. Furthermore, even in steel with lean Mn composition, the room temperature quenching and partitioning process combined with the chemically heterogeneous initial microstructure presented tensile properties comparable to those expected in steels with much higher Mn content, which exhibited the potential of heterogeneity-driven microstructure control for the development of advanced steel products.