Effect of intercritical deformation on tensile performance of a low-carbon Si–Mn steel processed by quenching and bainitic partitioning

Abstract

The effect of intercritical deformation on retained austenite and tensile performance of a low-carbon Si–Mn steel in modified quenching and bainitic partitioning processes was evaluated. The results showed that the intercritical deformation can play a positive role in stabilizing and refining the retained austenite, and possessed promising potential in balancing tensile strength and ductility of multiphase high-strength steels. The experimental low-carbon Si–Mn steel exhibited multiphase configuration comprising polygonal ferrite, granular bainite and granular structure after two different modified quenching and bainitic partitioning processes, and the bainitic ferrite laths got refined by intercritical deformation. The volume fraction of retained austenite in film-like and blocky morphology was increased from 11.5% to 13.9% due to applied intercritical deformation, and the larger amount of retained austenite provided the sufficient transformation-induced plasticity effect and resulted in enhanced work hardening degree; in response, enhanced ultimate tensile strength 1260 MPa and fracture elongation 22.1% were obtained, leading to increased product of strength and elongation in value of 27.7 GPa% compared to 20.8 GPa% of undeformed structure.