Near-A_c3 austenitized ultra-fine-grained quenching and partitioning (Q&P) steel

The influence of an intercritical anneal and a full austenitizing close to the A_c3 temperature on the mechanical properties of a quenching and partitioning (Q&P) processed medium Mn steel is reported. This approach to Q&P processing is shown to result in significantly improved mechanical properties mainly due to a refinement of the prior austenite grain size and, in consequence, the refinement of the lath martensite packet size after Q&P processing. Deformation twinning and strain-induced martensitic transformation were activated during tensile deformation. This resulted in a clear plasticity enhancement in the ultra-fine grained austenite islands after Q&P processing combined with austenitizing near the A_c3 temperature.