Structural and nitrogenation of Sm2Fe16Ti1 alloy prepared by HDDR process

Sm2Fe16Ti1Ny powder is synthesized by HDDR treatment and nitrogenation. As-cast Sm2Fe16Ti1 alloy has a few preferred directions. The main phase of Sm3(Fe,Ti)29 and the secondary phases of SmFe11Ti, SmFe2 or Sm(Fe,Ti)2 as well as little α-Fe(Ti) coexist in as-cast alloy. In the as-homogenized ingot, the main phase Sm3(Fe,Ti)29 still co-exists with Fe9.5SmTi1.5, SmFe11Ti and a few Sm-rich phases. When Sm2Fe16Ti1 alloy is treated by different cycles of HDDR process, the Sm2(Fe,Ti)17 main phase and a little α-Fe(Ti) present. Moreover, HDDR process contributes to the cracks of powder and grain boundaries. After the powder was nitrogenated for less than 12 h, the phase compositions are not changed any more, where the content of Fe-rich phases is increasing with respect to nitrogenation time. Moreover, the diffraction peaks of Fe-rich phases are little shifted to lower angle side. The nitrogenation process mainly includes two stages, one is fast reaction and diffusion between nitrogen atoms and Sm–Fe–Ti phases, the other is long-time homogenized diffusion of nitrogen. The optimal coercivity of 1859 Oe is obtained at nitriding 6 h, and the excellent magnetization of 126.4 emu g−1 and remanence of 48.3 emu g−1 are presented at nitriding 12 h.