Enhancing Mechanical Properties of Q&P Steel Through Tailoring Film-like Retained Austenite Morphology via Heating Rate Optimization

In this study, by regulating the heating rate, we have optimized the morphology of retained austenite in a quenching and partitioning (Q&P) steel with initial microstructure consisting of lath martensite. By optimizing the heating rate to 1 °C/s during the heating stage from 700 °C to 830 °C, the formation of blocky austenite and the coarsening of film-like austenite during the two-phase region annealing process were prohibited. Ultimately, this resulted in the production of Q&P steel containing a significant volume fraction (19.0%) of fine film-like retained austenite. This fine and film-like retained austenite exhibits higher stability than blocky austenite, exhibiting an active transformation-induced plasticity (TRIP) effect over a broad strain range. This results in excellent mechanical properties characterized by a high product of tensile strength and elongation (34.1 GPa·%).