Toughened austenitic stainless steel by surface severe plastic deformation

Deformation-induced nanocrystallization and martensite transformation were induced in the single surface of coarse-grained austenitic stainless steel sheet by severe plastic deformation, which formed the gradient, multiscale grain sizes distribution and composite microstructures of austenite and martensite. Resultant mechanical properties were optimized with improved yield strength of 1000 MPa (from the 300 MPa), large elongation to failure of 50% and good strain hardenability. Finally, observations on the deformation and fracture behavior clarify the inherent toughness mechanism.