Influence of Mechanical Milling on Microstructure and Electrochemical Properties of Mg<sub>2</sub>Ni Hydrogen Storage Alloy Prepared by Low-Temperature Solid-Phase Sintering

The alloy with the composition of Mg2Ni prepared by low-temperature solid-phase sintering was mechanically milled for 10, 25, 40 and 50 h. The microstructures and electrochemical properties of the Mg2Ni alloys were investigated by X-ray diffraction (XRD), optical microscope (OM) and electrochemical measurements. Furthermore, two broadening effects of XRD peaks caused by crystallite size and lattice strain were separated by the approximate function method and least square method. Crystallite size and lattice strain of the alloy were calculated. The results showed that sintered and milled alloys consist of the Mg2Ni phase. The milled alloys transform partly into nanocrystalline/amorphous structures during the milling process. By calculation, the crystallite size decreases and the lattice strain in the alloy decreases first and then increases with increasing milling time. The discharge capacities of the sintered alloy are significantly improved by milling. The maximum discharge capacities of the milled alloys increase with the increasing milling time.