Hot Deformation Behavior of a High-Mn Austenitic Steel for Cryogenic Liquified Natural Gas Applications

Hot deformation behavior of a high-Mn austenitic steel was investigated employing hot compression tests at different temperatures and strain rates. The flow behavior related to deformation temperature and strain rate was analyzed. Microstructures and grain boundary characteristics of the deformed specimens quenched at selected conditions were examined using SEM-EBSD. It was observed that the flow stress and critical characteristic parameters were sensitive to deformation temperature and strain rate. Grain boundary bulging was the main nucleation mechanism which signified discontinuous dynamic recrystallization played a vital role in microstructure evolution. Strain rate had a complex influence on DRX kinetics and the formation of Sigma 3 boundaries. At high strain rates, the higher stored energy and adiabatic temperature rise induced the boundary to migrate at a higher velocity, thus accelerating the nucleation of DRX grains and increasing the frequency of twinning. At low strain rates, longer time was available for grain boundary migration which facilitated the growth of DRX grains and the nucleation of annealing twins. However, at intermediate strain rates, sluggish recrystallization kinetics and annealing twins evolution were observed as the stored energy was not sufficiently high and the time available for grain boundary migration was also fairly short.