River-like dislocation channel unleashes high tensile ductility in as- cast refractory multi-principal element alloys

DC Cui and BJ Guo and B Xiao and QF Wu and ZJ Wang and JJ Li and L Wang and JJ Kai and QM Wei and JC Wang and F He, INTERNATIONAL JOURNAL OF PLASTICITY, 194, 104497 (2025).

DOI: 10.1016/j.ijplas.2025.104497

Dislocations govern the plastic deformability of structural alloys. However, this beneficial role is compromised in refractory multi- principal element alloys (RMPEAs), where tensile ductility degrades owing to plastic strain localization via planar slip and dislocation channeling. We proposed a ductilization concept based on engineered dislocation channels to divert and dredge dislocations, achieving a notable tensile ductility of 21 % and a yield strength exceeding the gigapascal mark in the as-cast RMPEA. To test the hypothesis that enhanced lattice distortion and chemical fluctuations act as dislocation diverters, we designed Ti53V15Hf32 (V15) and Ti41V27Hf32 (V27) RMPEAs with distinct volume misfit and Warren-Cowley parameters. In-situ synchrotron highenergy X-ray diffraction and transmission electron microscopy analyses revealed that increasing the volume misfit facilitates a transition in dislocation character from edge-based (V15) to screw-based (V27) under tensile loading. Atom probe tomography and high-angle annular dark-field scanning transmission electron microscopy characterizations further demonstrated that elevated V content engenders pronounced chemical fluctuations, inducing diversion of dislocation slip and the formation of river-like dislocation channels. These dislocation channels, on one hand, promoted dynamic strain hardening through dense intersections of the channel boundaries. On the other hand, they prevented premature necking and failure by enabling dislocations to proliferate and cross-slip within channels. Consequently, the river-like dislocation channels delayed plastic instability at ultrahigh yield strength, thereby enabling the RMPEA to unleash exceptional tensile ductility. These findings provide a dislocation-harnessing pathway for pursuing strength-ductility synergy in RMPEAs.

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