Recrystallization and grain growth of a nano/ultrafine structured austenitic stainless steel during annealing under high hydrostatic pressure

Abstract

The aim of this study was to investigate the effect of high hydrostatic pressure applied during annealing on the processes of recrystallization and grain growth in nanostructured austenitic stainless steel 316LVM. The nanostructures were obtained by profile rolling to a total strain of 3.4 and by high-pressure torsion to a total strain of 79. These processes resulted in microstructures consisting of nanotwins and nanograins, respectively. The deformed samples were annealed at 900 °C for 10 min under atmospheric or hydrostatic pressures of 2 and 6 GPa. The resulting microstructures were examined using transmission and scanning electron microscopy techniques. The mechanical properties were evaluated in microhardness measurements. It was established that annealing under high hydrostatic pressure retards recrystallization and grain growth, both in profile-rolled and high-pressure torsion-processed samples. The magnitude of retardation depends on the character of the grain boundaries. The non-equilibrium high-angle grain boundaries present in the high-pressure torsion-processed sample show higher mobility under pressure than the nanotwinned and low-angle boundaries in the profile-rolled sample.