Enhanced strain hardening and microstructural characterization in a low carbon quenching and partitioning steel with partial austenization

The high strength and good formability in low-carbon quenching and partitioning (Q−P) steels has been successfully obtained by full or partial austenization before Q−P process. In this regard, we have studied the effect of annealing conditions on the microstructural variation and the consequent strain hardening behaviors in a low-carbon Q−P steel. The microstructures of Q−P steels subjected to different annealing treatments were studied in details by a host of material characterization techniques including electron microscopy, electron microprobe and x-ray diffraction techniques. The study suggests that intercritical annealing is beneficial in increasing the volume fraction of retained austenite, which is the consequence of distribution of alloying elements during intercritical annealing and it enhances the stability of intercritically annealed austenite. Meanwhile, compared with the full austenitizing Q−P steel, the strain hardening of partial austenitizing Q−P steel is enhanced by the presence of intercritical ferrite and increasing volume fraction of retained austenite.