Ultra-grain-refinement of face-centered cubic high/medium-entropy alloys: Approaching the limit of grain refinement through severe plastic deformation and recrystallization

作者：Shuhei Yoshida, Nokeun Park, Kohei Shiotani, Yu Bai, Tomoaki Niiyama, Akinobu Shibata, Tomotsugu SHIMOKAWA, Nobuhiro Tsuji · 发表于：Materials & Design · 年份：2025 · DOI：10.1016/j.matdes.2025.114622 · 被引用次数：12 · 研究领域：High Entropy Alloys Studies、High-Temperature Coating Behaviors、Additive Manufacturing Materials and Processes

• Characteristics of recrystallization in FCC high entropy alloys (HEAs) were studied. • High-pressure torsion on HEAs resulted in nanocrystalline microstructures. • Significantly fine recrystallized microstructures were obtained after annealing. • Grain growth kinetics of HEAs were found to be much slower than pure FCC metals. • Slow grain growth can be due to solute drag enhanced by severe lattice distortion. Face-centered cubic (FCC) high- and medium-entropy alloys (HEAs/MEAs) develop fully recrystallized ultrafine-grained (FRex-UFG) microstructures after simple deformation and annealing processes. However, the mechanistic origins remain unclear. This study explains why FRex-UFG microstructures are readily formed in FCC HEAs/MEAs and clarifies their characteristics of microstructural evolution during deformation and recrystallization. CoCrFeMnNi HEA and CoCrNi MEA were subjected to high-pressure torsion (HPT) followed by short-term annealing. HPT-processed HEA and MEA showed finer nanocrystalline structures with higher dislocation densities than in conventional materials, indicating that dynamic recovery is more inhibited in HEAs/MEAs. Subsequent annealing produced FRex-UFG microstructures with grain sizes (with/without annealing twins) of 410/200 nm and 448/80 nm in the HEA and MEA, respectively, which are the smallest among single-phase materials reported to date. Grain-growth activation energies of the HEA and MEA were three times higher than that of pure Ni. Hybrid Mon...