Anomalous dynamic recrystallization during hot deformation in refractory high entropy superalloy: the role of grain boundary chemistry

Y Zhang and HY Li and JX Xu and YR Wang and W Wu and FH Cao and Z Peng and Y Chen and LH Dai, INTERNATIONAL JOURNAL OF PLASTICITY, 195, 104536 (2025).

DOI: 10.1016/j.ijplas.2025.104536

The limited understanding of thermomechanical deformation mechanisms in refractory high-entropy superalloys (RSAs) hinders the advancement of thermomechanical processing strategies for microstructure-property optimization. This study investigates hot-deformation and recrystallization behaviors of an Al0.5NbTa0.8Ti1.5V0.2Zr RSA, in which hot-deformation resulted in the formation of a characteristic necklace dynamic recrystallization (DRX) structure. The recrystallization fraction and grain size increase with rising temperature and decreasing strain rate, reaching maximum values of 19% recrystallized fraction and 16 mu m grain size. Both discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) mechanisms operate, in which DDRX dominates initial recrystallization, while recrystallized grains exhibit hybrid DDRX-CDRX mechanisms. The redistribution of Al and Zr promotes key recrystallization processes involving GB bulging and substructure development, revealing a diffusion assisted recrystallization mechanism. These findings provide the first direct evidence of the pivotal role of Al-Zr GB phase dissolve and diffusion on the recrystallization behavior. The present study featuring diffusion assisted recrystallization mechanism in Al0.5Nb-Ta0.8Ti1.5V0.2Zr RSA provided insights into the thermal deformation mechanism of analogous RSA and other BCC-HEAs.

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