Modification of Nano-Eutectic Structure and the Relation on Hydrogen Storage Properties: A Novel Ti-V-Zr Medium Entropy Alloy

TiV-based alloys present desired hydrogen storage properties owing to the formation of BCC solid solutions. However, nanostructure is scarce in these alloys though it can facilitate hydrogen absorption and desorption. In this study, Ti40Zr60-xVx (x = 20, 25, 30) alloys are prepared, and hyperfine nano-eutectic structures with lamellar space of 50–500 nm are formed, which can be refined by increasing Zr content. The Ti40Zr60-xVx alloys exhibit excellent activation and hydrogenation properties with high hydrogen storage capacities. The atomic size differences in the Ti40Zr60-xVx (x = 20, 25, 30) alloys can cause phase separation and nano-eutectic structure. Ti40V35Zr25 alloy achieves the fastest activation rate without incubation period, and the largest hydrogenation capacity of 2.4 wt.% is obtained within 10 min at 200°C under 1 MPa H2. The spinodal decomposition in Ti40V35Zr25 alloy facilitate the formation of an interconnected net-work eutectic phases, which can provide high-density phase interfaces and play a role of 'synergistic effect'. As a result, the hydrogenation kinetics and capacity are significantly enhanced.