Effect of Al content on the phase structure and the hydrogenation characteristic of La(Mg 1- xAl x) alloys

Abstract

La(Mg 1- x Al x ) ( x = 0.2, 0.4, 0.6, 0.8) alloys have been prepared using induction melting followed by annealing. It is found that partial substitution of Mg by Al does not lead to a change in crystal structure, and the alloys have a single LaMg phase when x ≤ 0.4. The lattice parameter of the LaMg phase decreases obviously after the partial substitution of Mg by Al. However, further substitution of Mg by Al leads to the coexistence of multiple phases when x ≥ 0.6. The alloys consist of the LaMg, LaAl, LaAl 2, and La 5Al 4 phases. The LaMg phase decreases, whereas the La 5Al 4 phase increases with the increase in x. The Al-substituted La(Mg 0.6Al 0.4) alloy can be hydrogenated into the tetragonal LaH 3, cubic LaH 3, MgH 2, and LaAl under 5 MPa at 473 K for 5 d.