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

• Equiaxed austenite with the smallest grain size ~ 80 nm was formed via three-stage cold rolling and annealing treatment.
• The nano/ultrafine-grained 304 stainless steel exhibited a combination of superior strength and good ductility.
• The yield strength, ultimate tensile strength, and elongation were 1120 MPa, 1440 MPa, and 12%, respectively.
• We confirmed that the mechanism of martensite reversion was diffusional type when samples were annealed at 550–650 °C.

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 ~ 150 nm (the smallest grain size was ~ 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 °C.

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