The Effect of Severe Plastic Deformation by High-Pressure Torsion on Structure and Phase Composition of High-Nitrogen Austenitic Steel

We study the effect of high-pressure torsion (6 GPa) for 0 (upset), 1/4, 1/2, and 1 revolutions at room temperature on the microstructure and microhardness of high-nitrogen austenitic steel Fe-18Cr-23Mn-2.7V-0.2C-0.7N (wt %). Slip, twinning, formation of localized microbands, and precipitation hardening are the main deformation mechanisms of steel under HPT. The level of solid solution hardening of steel after deformation remains as high as after quenching. As the result of severe plastic deformation, steel microhardness increases by 1.5 times. Mechanical twinning facilitates strain hardening due to high density of high-angle twin boundaries, prevents the formation of misoriented grain/subgrain structure with common type boundaries and contributes to the homogeneity of the structure and microhardness across the specimens.