Enhanced Mechanical Properties of Nano/Ultrafine-Grained Structure Formed by Martensite Reversion in 18Cr–8Ni Austenitic Stainless Steel

An NG/UFG austenitic stainless steel of type 18Cr–8Ni austenitic stainless steel was produced by strain-induced martensite phase reversion process. Severe cold deformation (70% reduction) at room temperature was carried out, followed by annealing in the conditions of 710 °C—10 min, 760 °C—5 min, and 950 °C—5 min. The nano/ultrafine grain size obtained was 400 nm, with the yield strength of 878 MPa and high ductility of 33%. The study of the deformation behavior of CG and NG/UFG steels found that the microstructure after ~11% tensile strain of NG/UFG steel included a number of dislocations and deformation twins. In addition, deformation bands and strain-induced martensite were observed in the deformed austenite grain. Whereas after ~11% tensile strain of CG steel, a large number of dislocations, stacking faults, and deformation bands were observed.