STRUCTURAL AND HYDRIDING PROPERTIES OF THE MG-NI-H SYSTEM WITH NANOMORPHOUS AND OR AMORPHOUS STRUCTURES/

The alloys Mg-x at.%Ni (x = 33, 35, 43 and 50) with different nanomete r-scale structures were successively synthesized by mechanical grindin g of Mg2Ni mixed with various amounts of additional Ni, and the relati ons between their structural and hydriding properties were investigate d in detail. The total hydrogen contents in these alloys increase from 1.7 mass% for x = 33 to 2.2 mass% for x = 43 and 50. This result is e xplainable by estimating both the volume fractions and the maximum hyd rogen contents of three regions in each alloy; the intra-grain region of nanostructured Mg2Ni, its inter-grain region, and the amorphous MgN i region. The dehydriding temperature lowers down to 373 K in the allo y composed of only the amorphous MgNi region, while the dehydriding ki netics of the alloy composed of the above three regions are faster tha n those of only the amorphous MgNi region. (C) 1997 Acta Metallurgica Inc.