The hydrogen pressure dependence of structural changes in C15 Laves phases TbM 2 (M = Fe, Co and Ni) were investigated between 0.1 and 5.0 MPa H 2 in order to elucidate conditions and the mechanism of hydrogen induced amorphization (HIA). General thermal reactions occur on heating as follows; hydrogen absorption in the crystalline state, hydrogen-induced amorphization (HIA), precipitation of TbH 2 (or TbNi 5 H x ) and decomposition of the remaining amorphous alloys. Exceptionally, a single-phase amorphous a-TbFe 2 H x was not formed below 0.2 MPa H 2 in TbFe 2 , because HIA and precipitation of TbH 2 simultaneously occurred. On the other hand, a single-phase a-TbNi 2 H x was not formed below 1.0 MPa H 2 because of the low hydrogen contents in c-TbNi 2 H x . The present work indicates that hydrogen absorption more than 1.0 (H/M) is essential for the occurrence of HIA in the C15 Laves phases TbM 2 .
K. Aoki, K. Mori, T. Masumoto