Ultrahigh strength nano/ultrafine-grained 304 stainless steel through three-stage cold rolling and annealing treatment

An approach involving grain refinement through three-stages of cold rolling and annealing was explored with 304 austenitic stainless steel to obtain ultrahigh strength. Equiaxed nano/ultrafine austenite grains of average grain size of similar to 150 nm (the smallest grain size was similar to 80 nm) was obtained with desirable combination of strength and moderate ductility (yield strength -1120 MPa, tensile strength -1440 MPa, and elongation -12%). The mechanism of transformation of martensite to austenite was diffusional reversion, when the specimens were annealed in the temperature range of 550-650 degrees C. (C) 2015 Elsevier Inc. All rights reserved.