Improved mechanical properties of mild steel via combination of deformation, intercritical annealing, and quench aging

Processing of dual phase steel with fine ferrite grains containing nanometric carbides and chain-like morphology of martensite from a 0.035C-0.005N-0.035Si-0.268Mn mild steel was realized via application of high cold rolling reductions, intercritical heat treatment, and room-temperature aging, which showed a yield stress (YS) of 450 MPa and ultimate tensile strength (UTS) of 700 MPa. It was revealed that significant enhancements in tensile properties can be achieved compared to the separate effects of intercritical annealing (YS of 130 MPa and UTS of 385 MPa), cold rolling and intercritical annealing (YS of 300 MPa and UTS of 600 MPa), and quench aging (YS of 275 MPa and UTS of 520 MPa). The results were rationalized based on the grain size strengthening, aging effect, and work-hardening behavior.