Effect of Laves phase on hydrogen storage properties of BCC Ti-V-Nb–Cr–Mn high entropy alloys

Abstract

The high entropy alloys (HEA) have demonstrated interesting properties, such as high capacity for hydrogen absorption at room temperature with easy activation. This study presents the results of research and development on HEA alloys within the Ti-V-Nb-Cr-Mn system for hydrogen storage applications. Alloy design was carried out using the CALPHAD method with Thermo-Calc software. The variation in Cr and Mn compositions, ranging from 9% to 12.5%, influences the phase fractions in the alloy's microstructure, including the BCC (body-centered cubic) solid solution and the Laves phase. The volume fraction and distribution of these phases can be modified through heat treatments, affecting the hydrogen-related properties of the alloys. The results revealed the formation of BCC and Laves phases, dependent on the alloy composition and heat treatment. Notably, alloys predominantly consisting of the BCC phase, with a minor fraction of Laves phase, demonstrated significant potential as hydrogen storage materials. Maximum absorption capacity values were observed, 2,2 wt% in the Ti_27.5V_27.5Nb₂₀Cr_12.5Mn_12.5 alloy and 2.9 wt% in the Ti₃₂V₃₂Nb₁₈Cr₉Mn₉ alloy. The kinetics and reversibility of the absorption and desorption processes were enhanced by a small amount of the Laves phase. These results highlight the potential of Ti-V-Nb-Cr-Mn HEA for efficient hydrogen storage applications.