V content modulates plastic deformation in Ti2Zr0.75NbVx medium-entropy alloys via lattice spacing, grain size, and dislocation synergy

In this study, Ti₂Zr_0.75NbV_x (x = 0.25, 0.5, 0.75, 1) lightweight medium-entropy alloys (LMEAs) were prepared via vacuum arc melting, and the influence of V content on the microstructure and mechanical properties was systematically investigated. The results show that with increasing V content, the lattice spacing and grain size gradually decrease, while the dislocation density and alignment are significantly enhanced. Among them, the V1 alloy, with the smallest lattice spacing and grain size (191.105 μm), exhibits the highest plasticity (16.8 % elongation). Molecular dynamics simulations further reveal that alloys with smaller lattice spacing possess lower dislocation formation energy, which significantly promotes dislocation nucleation and slip, thereby enhancing plastic deformation capability. Additionally, the formation of high-density parallel dislocation bundles optimizes stress distribution, delays local stress concentration and crack initiation, and further improves the alloy's plasticity. These findings provide critical theoretical insights for the design of high-performance lightweight alloys and lay a foundation for developing novel alloy materials with both high strength and high ductility.