Abstract
• Compositional variety of HDDR-synthesized TbCu 7 type Sm-Fe alloys is examined. • HDDR treatment is carried out for raw Sm-Fe alloys with various Fe-rich compositions. • TbCu 7 type Sm-Fe alloys synthesized by HDDR behaves like stoichiometric SmFe 8.5 alloy. • Transition from Fe-rich compositions to SmFe 8.5 occurs in a stage of HD reaction. Hydrogenation-disproportionation-desorption-recombination (HDDR) treatment of Fe-rich SmFe x alloys with x > 8.5 was conducted in order to investigate the possibility that the HDDR treatment can synthesize metastable TbCu 7 Sm-Fe phases with a Fe-rich composition, which are expected to provide large saturation magnetization . Fe-rich alloys prepared by melt spinning were HDDR-treated at 600 °C. As a result, the constituent phases of all the alloys transformed into non-Fe-rich TbCu 7 type SmFe 8.5 and iron phases in spite of the Fe-rich compositions of the original Sm-Fe phases. Thus, the TbCu 7 type Sm-Fe phase synthesized by HDDR treatment behaved as the stoichiometric compound of SmFe 8.5 . Electron microscope analysis revealed that the exclusion of excess iron from the original Sm-Fe phase occurred in the stage of disproportionation. In addition, the Sm-Fe phase prepared via a combination process of melt spinning and HDDR treatment had a very refined microstructure with grain sizes smaller than 100 nm, resulting in a large coercivity of 14.1 kOe after nitrogenization.
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