Harnessing competitive interplay between precipitation and lattice distortion for strong and ductile medium-entropy alloy
Jae Heung Lee, Hyeonseok Kwon, Gang Hee Gu, Jiyeong Lee, Sang Guk Jeong, Emad Maawad, Changwan Ha, Jaemin Wang, Byeong‐Joo Lee, Sangbong Yi, Takayoshi Nakano, Hyoung Seop Kim
Abstract
In Co-Cr-Fe-Ni-Mo-C ferrous medium-entropy alloys (FeMEAs), precipitation-driven alteration of matrix composition affects both the kinetics of deformation-induced martensitic transformation (DIMT) and the degree of lattice distortion. While DIMT has been well studied, the role of lattice distortion remains explored. In this study, we simultaneously enhance the strength and ductility in Co 18 Cr 13 Fe 57.5 Ni 7.5 Mo 3 C 1 (at%) FeMEA by harnessing the competitive interplay between precipitation and lattice distortion. Two annealed samples with similar grain sizes but different precipitate characteristics were prepared. The sample with suppressed precipitation exhibits improved ductility while maintaining comparable strength . The two specimens exhibited similar yield strengths due to a trade-off between precipitation strengthening and solid solution strengthening. However, the sample with higher lattice distortion and reduced precipitation demonstrates superior strain-hardening behavior owing to the lattice distortion-induced back stress, acting as an effective strain-hardening mechanism, and delayed DIMT, serving as a ductilizing mechanism. This work offers a strategy to modulate strengthening and deformation mechanisms in Co-Cr-Fe-Ni-Mo-C FeMEAs via precipitation control.