Design and mechanosynthesis of Low-Weight High-Entropy Alloys with hydrogen storage potential properties

Abstract

This investigation allows designed MgAl-based Low-Weight High-Entropy Alloys (LWHEAs) with a BCC-type structure, using a MgAlTi(X)Ni system where X = Fe, Cr and Co, with hydrogen storage potential properties. The BBC-type alloys were designed considering empiric thermodynamic parameters and obtained by high-energy ball-milling. The structure, morphology, thermal stability and hydrogen sorption properties were studied. Also, the influence of Valence Electron Concentration (VECmix) and Electronegativity difference (Δχmix) parameters on the hydrogen storage capacity of alloys was evaluated. The formation of the equiatomic MgAlTiFeNi, MgAlTiCrNi and MgAlTiCoNi BCC-type LWHEAs with densities between 4.3 ≤ ρ ≥ 4.6 g cm−3 was obtained at 8 h of milling. Alloyed powders show a homogeneous elemental distribution with heterogeneous particles of different sizes and a surface area of ∼ 2 g cm−2. Under high-temperature conditions, the LWHEAs structure changes from BCC to B2. The MgAlTiCoNi alloy presented a maximum hydrogen storage capacity of 2.1% weight H2 at 473 K and 1 MPa. The hydrogen storage depended on VECmix and Δχmix parameters in LWHEAs with the same mixing Entropy.