Effect of Ti/V ratio on the microstructure and mechanical properties of lightweight refractory Ti_(1-x)ZrNb_0.5V_(0.5+x) medium-entropy alloys

Lightweight refractory high/medium-entropy alloys (LRH/MEAs) are considered to have great potential for engineering applications owing to their light weight and exceptional mechanical performance. However, achieving a balance between strength and ductility remains a serious challenge, limiting their industrial applications. In this study, a series of Ti_(1-x)ZrNb_0.5V_(0.5+x) (x = 0–0.5) LRMEAs were synthesized by vacuum arc melting based on precise compositional adjustments, and the effects of the Ti/V ratio on both the microstructure evolution and mechanical properties was comprehensively investigated. With increasing x values, the phase structure changes from a single BCC phase to a multiphase system consisting of BCC#1, BCC#2 and α-Zr phases, where the proportion of the BCC#2 and α-Zr phases increase from 0 % to 29.65 % and 25.46 %. This phase evolution increases the compressive strength and hardness, but decreases the ductility. The yield strength varies from 888 MPa (x = 0) to 1224 MPa (x = 0.4), and the Ti_0.6ZrNb_0.5V_0.9 alloy achieves an optimal strength-ductility balance due to the uniform distribution of BCC#2 and α-Zr phases. These findings highlight the critical influence of Ti/V ratios on phase composition and mechanical performance, providing a framework for optimizing alloy design to advance lightweight materials for high-performance engineering applications.