The Influence of Tempering Parameters on the Microstructure, Mechanical Property, and the Corresponding Strengthening Mechanism of Metastable 301 Austenitic Stainless Steel

Metastable austenitic stainless steels (MASS) are widely used in various industrial applications due to their exceptional mechanical properties. The microstructure of MASS can be regulated through severe plastic deformation, heat treatments, and surface treatments to achieve further improvement of mechanical properties. Herein, nanograin and quasiheterostructure are prepared by cold rolling and annealing process in Fe–17Cr–6Ni MASS. The mechanical response, deformation mechanism, and strengthening contribution of the two steels with representative microstructure are studied. The results indicate that nanograin austenitic steel (803 MPa, 22%) has superior yield strength and similar ductility compared with that of quasiheterostructure steel (600 MPa, 25%). In the nanograin steel, the deformation mechanism is mainly dislocation slip and deformation-induced martensite transformation, while in quasiheterostructure steel, the deformation twinning is also included for the relative lower stacking fault energy in the coarse grain. The yield strength of nanograin structural steel is about 200 MPa higher than that of quasiheterostructure steel, which can be attributed to the differences in grain refinement strengthening, phase-transformation strengthening, and precipitation strengthening of Cu particles. The findings presented in this study are informative for modulating MASS properties and ultimately improving the lifespan in a variety of industrial settings.