A single-phase Nb25Ti35V5Zr35 refractory high-entropy alloy with excellent strength-ductility synergy
Junjie Gong, Wenjie Lu, Yan Li, Shilong Liang, Yongxin Wang, Zheng Chen
Abstract
Refractory high entropy alloys (RHEAs) are promising candidates for high-temperature structural materials due to their excellent high-temperature performance. However, the room-temperature brittleness of most alloys results in poor plastic formability, thereby limiting their engineering applications . In this study, Nb 25 Ti 35 V 5 Zr 35 alloy with cold-rollability was developed, and its phase stability, tensile mechanical properties, elastic properties, strengthening mechanism , and deformation mechanism were investigated by combining experiments, CALPHAD, DFT and molecular statics (MS) methods. The results demonstrate that Nb 25 Ti 35 V 5 Zr 35 alloy possesses good phase stability, with both the as-cast and annealed states maintaining a single-phase BCC structure without undergoing phase transformation. The tensile yield strength of the alloy reaches its peak at 1152 MPa in the cold-rolled condition, while its annealed state exhibits an optimal balance of strength and plasticity, with a yield strength of 836 MPa and an elongation of 22.45 %, respectively. Solid solution strengthening is the primary source of its high strength, with V and Zr playing key roles in this strengthening mechanism. Dislocation slip plays a dominant role in plastic deformation . Additionally, compared to traditional BCC alloys, the significance of edge dislocations in the deformation process is notably enhanced, with the { 112 } plane serving as the preferred slip plane for dislocations. DFT results indicate that the alloy exhibits significant anisotropy in both Young's modulus and shear modulus . This work contributes to understanding the material properties of the Nb 25 Ti 35 V 5 Zr 35 alloy and provides a reference for the design of new ductile RHEAs.