By thermal analysis of DyFe 2: (1) hydrogen absorption; (2) hydrogen-induced amorphization (HIA); (3) the precipitation of BiF 3-type DyH 3; and (4) the decomposition of the remaining amorphous hydride occur exothermically with increasing temperature at 1.0 MPa H 2. T p/T m (the peak temperature/the melting temperature of DyFe 2) for hydrogen absorption, HIA, the precipitation of DyH 3 and the decomposition of the amorphous hydride are 0.28, 0.36, 0.43 and 0.48, respectively, which are closely related with kinetics of the transformations. The peak temperature T p for HIA shows a large and negative pressure dependence, but that for the precipitation of DyH 3 shows a small and positive one. As a consequence of such pressure dependence, HIA overlaps with the precipitation of DyH 3 at 0.2 MPa H 2, while the crystalline hydride decomposes directly into α-Fe and DyH 3 at 0.1 MPa H 2. The activation energy E A for hydrogen absorption, HIA, the precipitation of DyH 3 and the decomposition of the amorphous hydride are calculated to be 56, 75, 308 and 162 kJ/mol Dy, respectively, which are closely related with the mechanism of HIA. The mechanism of HIA is discussed on the basis of the experimental results.
All Science Journal Classification (ASJC) codes
- Mechanics of Materials
- Mechanical Engineering
- Metals and Alloys
- Materials Chemistry