Evolution of Twin Boundaries and Contribution to Dynamic Recrystallization and Grain Growth of Inconel 625

Dynamic recrystallization (DRX) and grain growth behaviors of Inconel 625 alloy are investigated via hot compression test in the temperature range of 900–1200 °C and strain rate range of 0.01–10 s⁻¹. The electron backscatter distribution technique is an effective method for identifying twin boundary evolution on the basis of temperature and strain rate; this approach is applied in this study to investigate the effects of twins on the DRX process and grain growth. The fraction of DRX increases with temperature under all strain rates, but the strain rate exerts a complex effect on DRX. Grain size variation with temperature follows a similar trend of declining and then increasing, whereas no apparent trend is observed at various strain rates. The DRX mechanism of the Inconel 625 alloy shifts from discontinuous DRX to continuous DRX with a reduction in deformation temperature and increase in strain rate. The fraction of Σ3ⁿ (n = 1, 2, 3) boundaries (twin boundaries) increases with increasing temperature at low temperatures (<1100 °C), but declines with increasing temperature at high temperatures (≥1100 °C). At low temperatures (<1100 °C), the fraction of Σ3ⁿ (n = 1, 2, 3) boundaries declines with an increasing strain rate up to 1 s⁻¹ and then increases.