Microstructure and remarkably improved hydrogen storage properties of Mg2Ni alloys doped with metal elements of Al, Mn and Ti

Mg2Ni0.7M0.3 (M=Al, Mn and Ti) alloys were prepared by solid phase sintering process. The phases and microstructure of the alloys were systematically characterized by XRD, SEM and STEM. It was found that Mg3MNi2 intermetallic compounds formed in Mg2Ni0.7M0.3 alloys and coexisted with Mg and Mg2Ni, and that radius of M atoms closer to that of Mg atom was more beneficial to the formation of Mg3MNi2. The hydrogen storage properties and corrosion resistance of Mg2Ni0.7M0.3 alloys were investigated through Sievert and Tafel methods. Mg2Ni0.7M0.3 alloys exhibited remarkably improved hydrogen absorption and desorption properties. Significantly reduced apparent dehydriding activation energy values of -46.12, -59.16 and -73.15 kJ/mol were achieved for Mg2Ni0.7Al0.3, Mg2Ni0.7Mn0.3 and Mg2Ni0.7Ti0.3 alloys, respectively. The corrosion potential of Mg2Ni0.7M0.3 alloys shifted to the positive position compared with Mg2Ni alloy, e.g. there was a corrosion potential difference of 0.110 V between Mg2Ni0.7Al0.3 alloy (-0.529 V) and Mg2Ni (-0.639 V), showing improved anti-corrosion properties by the addition of Al, Mn and Ti.