Effects of strain rates and twins evolution on dynamic recrystallization mechanisms of austenite stainless steel

The isothermal compression (1050 °C) of a 304-type austenite stainless has been employed to understand the roles of strain rates (0.001, 0.01, 0.1, 1, and 10 s−1) and twinning in flow behaviors and microstructure evolution. Using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) analysis, it was determined that the alloy underwent discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) in low and high strain rate regimes, respectively. In the low strain rate regime, twinning contributed to the separation of the bulged region for dynamic recrystallization (DRX) nucleation, and Σ3 twin boundaries mainly formed by ‘growth accident’ during the subsequent growth of nuclei. In the high strain rate regime, twinning did not require boundaries migration, and altered the orientation of boundary fronts, thus promoting the extension of the DRX area. Grain size exponents in low and high strain rate regimes were calculated to be −0.68 and −2.9, respectively. It was also confirmed that different DRX mechanisms result in distinct evolution of grain size, and the dividing point was determined to be the strain rate of 0.1 s−1. •Effects of strain rate on flow behaviors and microstructure evolution during hot deformation were analyzed using TEM and EBSD.•DDRX and CDRX mechanisms for different strain rate regimes were proposed.•Twinning mechanisms for two types of DRX were clarified to be different.•Grain size exponents were calculated to be −0.68 and −2.9 in low and high strain rate regimes, respectively.