Effect of Y Substitution on Hydrogen Storage Performance of AB₂-type LaMgNi₄ Alloys

Hydrogen-induced-amorphization is prevalent in rare earth AB₂-type alloys. La_1-xY_xMg Ni_3.8Al_0.2（x=0-0.4） alloys were refined using a vacuum induction melting furnace, and the phase structure, microstructure and hydrogen sto rage properties of the alloys were tested and analyzed using XRD, SEM and P-C-T hydrogen storage tester. The results show that the alloy consists mainly of LaMgNi₄ and La（NiAl）₅ phases, with an additional Ni₃Y phase appearing when x≥0.1. The alloys after hydrogenation consist of LaMgNi₄H_4.85and La_0.91（Ni Al）₅H_4.43phases, with a small amount of YH₂ phase occurring in the Y-containing alloy. The as-cast alloys are acicular structure and become more homogeneous and refined as the amount of Y substitution increases. Y substitution significantly improves the activation properties of the alloys. The maximum hydrogen uptake of the alloys with x=0, 0.1, 0.2, 0.3, and 0.4 at 313 K temperature and 3 MPa hydrogen pressure are 1.663 wt%, 1.656 wt%,1.63 2 wt%, 1.635 wt%, and 1.641 wt%, respectively. The alloy with x=0.1 has the best kinetics with 1 min hydrogen uptake reaching 85.2% of the maximum hydrogen uptake. The ΔH of the alloy increases with increase of Y content. The alloy with x=0.3 has the best cycling performance with capacity retention of 81.67% after 50 cycles.