Probing deformation processes in near-defect free volume in high strength–high ductility nanograined/ultrafine-grained (NG/UFG) metastable austenitic stainless steels

The deformation behavior of a nanograined/ultrafine-grained (NG/UFG) austenitic stainless steel characterized by high strength–high ductility combination is investigated via nanoindentation and electron microscopy, and the behavior compared with its coarse-grained (CG) counterpart. In NG/UFG steel, mechanical twinning was an active deformation mechanism, while in CG steel, nucleation of strain-induced martensite at the shear bands occurred. The differences in deformation mechanisms of NG/UFG and CG steels are reflected in the discrete burst in the force–displacement plots and attributed to austenite stability.