Abstract: The effect of Mg replacement with Al on the discharge capacity of Mg₂Cu powder mixture was investigated. The mixture of nanocrystalline powder was prepared via mechanical alloying (MA) technique with a high energy planetary ball mill. In addition, different moles of Al (0.05, 0.1, 0.15, 0.2, and 0.3 M) were substituted to Mg₂Cu powder. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to analyze changes in structure, morphology, and grain size. The obtained powder was utilized as an anode in a nickel–metal hydride battery (Ni–MH). In the specimens with 0.05 M Al content, the orthorhombic structure of Mg₂Cu is emerged after 5 h milling. The results reveal that more than 0.1 M Al substitution leads to an appearance of MgCu₂ peaks. Al substitution does not affect microstructure uniformity; however, it causes a decrease in crystalline size and lattice parameters. The selected area diffraction (SAD) pattern elucidates that the electrode with the Mg_1.9Al_0.1Cu chemical composition and 20 h milling has the maximum discharge capacity.