Study on Microstructure and the Hydrogen Storage Behavior of a TiVZrNbFe High-Entropy Alloy

High-entropy alloy has shown great potential in the field of hydrogen storage owing to its lattice distortion capacity and the breadth of the compositional design. In this work, the microstructure and hydrogen storage properties of an equimolar TiVZrNbFe were investigated. The results show that the TiVZrNbFe alloy consists of C14 phase and Nb-based solid solution phase. C14 hydride and FCC dihydride are formed after hydrogenation, while C14 phase and BCT monohydride are formed after dehydrogenation. The difference in the hydrogen desorption behavior between the two phases stems from the difference in valence electron concentration (VEC). The hydrogen storage properties tests show that the alloy can absorb 1.60 wt % hydrogen at 50 degrees C under 1 MPa H-2 in only 100 s. The hydrogenation mechanism was identified as nucleation and growth of hydrides based on two-step hydrogen absorption, and its apparent activation energy (EA) for hydrogen absorption is lowered to 11.27 kJ/mol H-2. The decomposition process of corresponding hydride can be divided into four stages, which reveals that the hydrogen is desorbed from four different types of interstitial positions.