Continuous Dynamic Recrystallization Nucleation Mechanism and Annealing Twin Evolution with Respect to Grain Growth in a Nickel-Based Superalloy

The hot compression deformation behavior of a nickel-based superalloy was characterized by electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) techniques. The main microstructure characteristics of the studied superalloy after hot compression deformation featured the development of subgrains, dynamic recrystallization (DRX) nuclei, DRX grain growth, and annealing twins. Considering the approximate orientation between deformed grains and the dynamic recrystallization results, we concluded that the continuous dynamic recrystallization (CDRX) nucleation mechanism characterized by subgrain bonding and rotation played a major role at low temperatures and high strain rate in addition to twinning-assisted recrystallization nucleation. The presence of MC and γ′ phase precipitated phases at low temperatures (900 and 1000 °C) facilitated the nucleation of DRX but hindered the growth of recrystallization. Grain growth at high deformation temperatures depended on the mutual annexation of grains induced by high-angle grain boundary migration, which consumed part of the annealing twins, and only a few annealing twins remained stable after orientation deflection.