Deformed nanotwins promoted by grain refinement in austenitic stainless steel and its characteristics

Although the grain refinement by severe plastic deformation can obtain outstanding mechanical strength, this usually involves sacrificing the plasticity of the materials. This work therefore provided a simple processing route to achieve strength and plasticity by twice cold rolling and reversed transformation annealing for the 316L stainless steel to optimize the recrystallized microstructures. Our study revealed that applied approach of twice cold rolling and reversed transformation annealing dramatically improved strength and retained better ductility in nano/ultrafine grained 316L stainless steel. The results obtained by the transmission electron microscopy indicated that the grain refinement facilitated the forming of deformed nanotwins in austenitic stainless steels. The high strength was attributed to grain refinement, α′-martensite transformation and nanotwin, while excellent ductility resulted from α′-martensite transformation and grain boundary slip or rotation.