HDDR of Sm–Co alloys using high hydrogen pressures

Effect of hydrogen on the phase–structure transformations in ZrCrNi alloy

“…Unlike ferromagnetic materials based on REM 2 Fe 14 B compounds, which disproportionate at hydrogen pressures ≤0.1 MPa, the Zr-based compounds do not decompose under such conditions [8]. Analogously, as for the very stable Co-based compounds [19,20] and alloys with CaCu 5 type structure (such as LaNi 5 ) [21,22], high pressure was used for carrying out of the HDDR process of the ZrCrNi alloys.…”

“…The series of phase transformations occurring during heating in hydrogen was determined both for single phase alloys based on LaNi 5 [19,20] and for Zr-based multiphase alloys with Laves phase structure. In the ZrCrNi-H 2 system, besides Laves phase hydride formation, two exothermic (at 535 and 675 • C) and two endothermic (at 791 and 819 • C) transformations were determined.…”

Features of the HDDR process in alloys based on the SmCo5 compound

“…Gutfleisch et al [3] revealed that the disproportionation in ferromagnetic samarium-cobalt compounds takes place in a process of reactive mechanical milling in a vibration mill under hydrogen pressure around 0.5 MPa and at a temperature of 350 • C. This approach allows the material to be obtained in nanocrystalline state. Besides, it was shown that the alloys based on SmCo 5 and Sm 2 Co 17 compounds disproportionate into samarium hydride and cobalt at the initial hydrogen pressures 1.0-4.0 MPa and than recombine with the formation of the initial phase after heating in vacuum [4,5]. The authors of the above articles revealed that a coercivity of the materials based on SmCo 5 and Sm 2 Co 17 compounds increases after the carrying out of the HDDR process.…”

Features of the HDDR process in ZrT2 (T = Cr, Mn, Fe, Co) compounds

“…Compounds of different compositions, from Nd-Fe-B to (Nd, Pr, Ce, La)-Fe-B, have fallen into the field of vision of the researchers of the HDDR process [4][5][6]. Moreover, it has been shown, that the HDDR process exists not only in ferromagnetic alloys of REM-Fe-B systems, but also in other intermetallic compounds [7][8][9][10][11].…”