EFFECTS OF NANOMETER-SCALE STRUCTURE ON HYDRIDING PROPERTIES OF MG-NIALLOYS - A REVIEW

The materials, which are produced by mechanical grinding/alloying, pos sess superior hydriding properties depending on their nanometer-scale structures. In this review paper, we present our recent works on the h ydriding properties and nanometer-scale structures of some mechanicall y produced Mg-Ni alloys. The first topic is the properties of some nan ostructured Mg2Ni (Mg-33 at%Ni) consisting of nanometer-scale crystall ite (intra-grain) and inter-grain regions. In this system, the existen ce of the inter-grain region gives rise to notable hydriding propertie s of the nanostructured Mg2Ni such as the enhanced hydrogen dissolutio n and low-temperature dehydriding. The second topic is the properties of the alloys Mg-33, 38, 43 and 50 at% Ni in which a different amount of the amorphous (a-)MgNi phase depending on Ni content is homogeneous ly dispersed around nanometer-scale Mg2Ni crystallites. In this system , the total hydrogen content increases with increasing Ni content. Thi s experimental result is well explained by a model based on three nano structural constituents of these alloys and their hydriding properties . (C) 1997 Elsevier Science Limited.