Superior strength and ductility of 316L stainless steel induced by micro/nano/ultrafine-grains multiphase complex structures

Abstract

Achieving combination of superior strength and good ductility is desirable for advanced structural and functional steels materials for their applications. In present study, a heterogeneous 316L austenite stainless steel with high strength and good ductility was designed, which consisted of micro/nano/ultrafine-grains (UFG) multiphase complex structures. The special heterogeneous microstructure was fabricated by cold rolling and subsequent annealing. The results demonstrated that the heterogeneous microstructure consisted of 28.04% micro-grains, 59.96% ultrafine-grains and 12% nano-grains. The high yield strength (920 MPa) and tensile strength (1162 MPa) originates from heterogeneous micro/nano crystalline (fine-grain strengthening) and duplex phases microstructure. As well as the increase of recrystallized grains and decrease of defects, the high work hardening capability of the composite structure of a soft micro-grained matrix embedded with hard nano-grain particles is responsible for its good uniform elongation (14.3%). This processing technique is conductive to achieve superior combination of strength and ductility by controlling size of micro/nano/ultrafine crystalline and their volume fraction.