Microstructure and mechanical properties development of nano/ultrafine grained AISI 316L austenitic stainless steel prepared by repetitive corrugation and straightening by rolling (RCSR)

Abstract

In the present work, microstructure and mechanical properties development of AISI 316L austenitic stainless steel, heavily deformed by repetitive corrugation and straightening by rolling (RCSR) process were investigated. Microstructural evolution of processed specimens was studied by electron back scattered diffraction (EBSD) analysis and revealed that nano/ultrafine grains with the average grain size of 200 nm after 40 RCSR cycles. The fraction of high angle grain boundaries and mean misorientation were represented increased by increasing the strain during the RCSR process and reached to a saturated value of 76% and 36.69°, respectively. It was observed that repetitive corrugation and straightening by rolling process was a promising process for metastable austenite transformed to α′-martensite. The RCSR processed specimen exhibited the yield strength, tensile strength, and microhardness of about 948 MPa, 956 MPa, and 340 HV compared with starting material (355 MPa, 672 MPa, and 190 HV) after 40 cycles. Scanning electron microscopy (SEM) observations of tensile fracture surface of specimens revealed ductile type fracture. Also, more ductile fracture occurs in the specimens subjected to higher number of RCSR cycles. It was suggested that the transformation of austenite to martensite affected the work hardening of the specimens which inhibits localized deformation during necking and postpones the fracture.