Hydrogen absorption in a stable icosahedral (i-) Zn50Mg42Y8 alloy has been studied by X-ray diffraction, transmission electron microscopy and differential scanning calorimetry. The i-phase decomposed to a hexagonal Zn2Mg Laves phase, YH3 and MgH2 after hydrogenation under 3 MPa hydrogen pressure at 573 K for 259.2 ks. Two stages of hydrogenation for the i-phase were identified; i-ZnMgY+xH2→i-ZnMgYH2x in the initial stage and then i-ZnMgYH2x+H2→Zn2Mg+YH 2+MgH2. DSC curve of the fully hydrogenated (3 MPa, 573 K, 259.2 ks) sample revealed an endothermic peak around 730 K corresponding to the hydrogen desorption. The transformations between the icosahedral and crystalline phases due to hydrogen absorption and desorption are reversible.
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