Structure and hydrogen storage properties of a high entropy ZrTiVCrFeNi alloy synthesized using Laser Engineered Net Shaping (LENS)

Abstract

In this work, the ZrTiVCrFeNi high entropy alloy was successfully synthesized from elemental powders near the equimolar ratio using Laser Engineered Net Shaping (LENS). The prepared alloy exhibited good chemical composition after laser deposition, compared to the nominal composition, which was further improved using high-temperature annealing at 1000 °C for 24 h. Better powder quality and the optimization of the LENS parameters are still necessary for obtaining the improved chemical homogeneity of the alloy after synthesis. The alloy exhibited a two-phase structure, i.e., the dominant C14 Laves phase matrix with a minor amount of the α-Ti solid solution, after synthesis and annealing. The PCT isotherms were measured up to 100 bar of hydrogen pressure at 50 °C after activation of the alloy by annealing at 500 °C for 2 h under vacuum. The obtained maximum hydrogen capacity was 1.81 wt.% after synthesis and 1.56 wt.% after additional annealing. The equilibrium pressure of hydrogen desorption was too low for a complete desorption reaction, resulting in the presence of a C14 hydride phase in the alloy after PCT tests.