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

• Published in: Materials characterization Vol. 198; p. 112727
• Main Authors: Kang, Dong-Soo, Lee, Hyungsoo, Yun, Dae Won, Jeong, Hi Won, Yoo, Young-Soo, Seo, Seong-Moon
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.04.2023
• Subjects: Directional solidification; Dynamic recrystallization; High-temperature creep deformation; Ni-based superalloy; Directional solidification; Ni-based superalloy; Dynamic recrystallization; High-temperature creep deformation
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/j.matchar.2023.112727

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. [Display omitted] •Study of mechanism of nucleation and growth of dynamic recrystallization (DRX).•Local stress concentration around cavity tip produced DRX-triggering driving force.•Dynamic recovery by LAB formation produced initial nucleation of 15% dynamic strain.•Continuous DRX was dominant mechanism in DS CM247LC during high-temperature creep.