Influence of DIMT on impact toughness: Relationship between crack propagation and the ??-martensite morphology in austenitic steel

The trade-off between transformation-induced plasticity (TRIP) strengthening and the intrinsically brittle nature of deformation-induced ??-martensite (DIM) has been a long-standing dilemma in optimizing strength–toughness synergy austenitic steels. This limited their potential use, particularly energy absorption applications. Here, we propose new strategy to minimize negative effect without limiting TRIP. In this study, 321 stainless steel samples with different austenite grain sizes (AGSs) were fabricated tailor DIM morphology. morphology on crack propagation was simultaneously evaluated. Electron channeling contrast imaging (ECCI) selected area electron backscattered diffraction (EBSD) Charpy fractures reveals that lath-like effectively deflects cracks increases (Ep). As consequence, coarse-grained ultra-coarse-grained (CG/UCG) steels can achieve high strength resistance, while ultra-fine-grained (UFG) blocky exhibits lowest Ep. Furthermore, is controlled by its nucleation sites adjacent crystallographic/phase boundaries. twins or ?-? boundaries promote formation ??-martensite. ?????? transformation sequence be explained change stacking fault (SFE), which provides further guidance for design toughness.