Hard magnetic properties of quenched Sm-Fe-N powders

Sm-Fe-N hard magnetic materials are good candidates for high performance bonded magnets. Rapid-quenching method should be highly favorable for the fabrication of isotropic magnet powder with high coercivity. We report here the magnetic properties of Sm-Fe-N powders produced by a few kinds of rapid-quenching processes. Sm2Fe17 powders were prepared by gas-atomization (GA), rotating-disk atomization (RDA), or melt-spinning (MS) method. The H-cJ Sm2Fe17 GA powder had dendritic solidification structure, while the RDA powder had microcrystalline structure with size of 3-5 mum Coercivities (H-cJ) of their nitrides were 56 (for GA) and 217 kA/m (for RDA). The of nitrided Sm2Fe17 MS powder with wheel velocity (V-s) of 5-20 m/s, which had also microcrystalline structure, was 53 to 509 kA/m. These coercivity values are not sufficient for bonded magnet applications. From the study of additive effects, it was found that C, C-Si, C-Ga, or C-AL addition decreased the crystal size of quenched Sm2Fe17 powder. Consequently, high coercivity was obtained; the II, of nitrided Sm2Fe17C1Si1 MS powder with V-s of 10 m/s was 898 kA/m, and 708 kA/m fdr the nitrided Sm2Fe15C1Si2 RDA powder. The compression-molded bonded magnet made from Sm2Fe18Si0.1Nx MS powder showed a high (BH)(max) of 82.7 kJ/m(3).