Extra work hardening in room-temperature quenching and partitioning medium Mn steel enabled by intercritical annealing

Abstract

The present work applies an intercritical annealing process on a room-temperature quenching and partitioning (RT Q&P) medium Mn steel. It is found that the intercritical annealing maintains the amount of austenite while improves its mechanical stability. The reverse transformation during the intercritical annealing competes with the martensitic transformation during the quenching, resulting in a similar quantity of austenite after the intercritical annealing. Both reverse transformation and martensitic transformation help to refine the austenite grain size and facilitate C enrichment, enhancing the austenite stability. The intercritical annealing improves both ultimate tensile strength and uniform elongation of RT Q&P medium Mn steel, which is ascribed to an extra work hardening resulted from the improved austenite stability.