Study of the Structural and Phase State and Hydrogen Interaction of a TiZrNbVTa High-Entropy Alloy Prepared by SPS

The effects of post-processing heat treatment on the structural and phase state and hydrogen sorption characteristics of an equiatomic TiZrNbVTa high-entropy alloy produced by mechanical activation and spark plasma sintering were investigated. The powder mixture was mechanically activated under argon and consolidated at 1450 °C. Two processing conditions were compared: SPS with a 7 min hold without subsequent treatment, and SPS with a 5 min hold followed by annealing at 1050 °C for 5 h. Phase composition was analyzed by X-ray diffraction. Hydrogenation was performed at 400–600 °C under a hydrogen pressure of 37–40 bar. Hydrogen content was evaluated using the SOAK kinetic method and inert gas fusion analysis with a RHEN-602 analyzer. Both materials were predominantly composed of a Nb-enriched body-centered cubic phase, whereas their secondary-phase compositions differed. After annealing, weak reflections tentatively attributed to ZrO2 and TaO2 appeared, whereas reflections previously assigned to Zr, V, and TiO2 could no longer be resolved. According to the RHEN-602 measurements, the hydrogen content ranged from 1.12 to 1.37 wt.% for the SPS sample and from 0.64 to 2.08 wt.% for the SPS-HT sample between 400 and 600 °C. These results indicate that processing involving high-temperature annealing modifies the phase state and may enhance hydrogen uptake at 500–600 °C.