Exploring the Dual-Phase Configuration of Multicomponent Alloys in the Ti₂₁Zr₂₁VxFeyNiz (x + y + z = 58 at %) System for Room Temperature Hydrogen Storage

This study investigates the dual-phase configuration of multicomponent alloys (MCAs) within the Ti21Zr21VxFeyNiz (x + y + z = 58 at %) system for hydrogen storage. The design strategy involved the use of the Calculation of Phase Diagrams (CALPHAD) method, which obtained four dual-phase alloys with varying proportions of C14 Laves and body-centered cubic (BCC) phases. All alloys exhibited fast hydrogen absorption kinetics, reaching maximum capacity within 5 min, and demonstrated good hydrogen storage capacity at room temperature. Ti21Zr21Fe41Ni17 (V1), with the lower BCC content (8.2 wt %), absorbed the lowest amount of hydrogen (1.2 wt %), whereas Ti21Zr21V14Fe4.3Ni39.7 (V4) absorbed up to 1.7 wt %. When analyzing the thermodynamics of the alloys, V1 exhibited a superior reversible hydrogen capacity of 0.91 wt % when compared to V4, which retained 0.56 wt %. This behavior is attributed to the thermodynamic stability of the C14 Laves phase, which predominantly governs the absorption characteristics at room temperature, as confirmed by pressure–composition–temperature (PCT) simulations, and to hydrogen retention within the BCC structure.