Relationship of grain size and deformation mechanism to the fracture behavior in high strength–high ductility nanostructured austenitic stainless steel

In this study we underscore the dependence of grain structure and deformation mechanism on the fracture behavior in a high strength–high ductility bearing nanograined/ultrafine-grained austenite stainless steel. In high strength nanograined steel, deformation twinning contributed to excellent ductility, while in the low strength coarse-grained steel, the high ductility is attained as a consequence of strain-induced martensite transformation. Interestingly, the differences in deformation mechanism of steels deformation mechanisms of steels with different grain structures but with similar elongations influenced the mode of fracture, a behavior that is governed by the change in austenite stability with grain size. The areal density of voids and their average diameter in the fracture surface also increased with increasing grain size, which ranged from 320 nm to 22 μm.