Carbon content-tuned martensite transformation in low-alloy TRIP steels

Ultrahigh strength and good ductility are obtained for two low-alloy transformation-induced-plasticity steels fabricated by the quenching and partitioning (Q&P) processing, respectively. Compared to 0.19 wt.% C steel in which γ → α′-martensite transformation is the dominant mechanism under deformation, the relatively high C content of austenite in 0.47 wt.% C steel is responsible for the transformation from γ to ε-martensite, suggesting that the transformation is not solely determined by the stacking fault energy. The study shows that during the Q&P process, strong and ductile steels with specific transformation procedures can be obtained by adjusting volume fraction and carbon content of the retained austenite.