Microstructural mechanism of local dynamic recrystallization around cavity during tertiary creep in directionally solidified superalloy CM247LC

This study investigated the mechanism of nucleation and growth of dynamic recrystallization (DRX) locally occurring around a cavity depending on the creep strain at 982 °C under 180 MPa in directionally solidified superalloy CM247LC. Misorientation increased when the creep strain reached 15%, and low-angle boundaries along rafted γ–γ’ around the cavity formed a high-angle boundary, which is assumed to be the initial nucleation mechanism of recrystallization. Further deformation increased the dislocation density in the recrystallized grains, resulting in post-DRX via fast dynamic recovery. The γ matrix was coarsened by the atomic diffusion of Co and Cr along the dislocation line in the γ’ phase of the recrystallized grains.