Magnetic Properties of Nitrided Sm-Fe Powder Prepared by Atomization and Melt-Spinning Processes

摘要

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 three kinds of rapid-quenching processes. Sm_2Fe_(17) powders were prepared by gas-atomization (GA), rotating-disk atomization (RDA), and melt-spinning (MS) methods. The Sm_2Fe_(17) GA powder had dendritic solidification structure, while the RDA powder had microcrystalline structure with size of 3-5 #mu#m. Coercivities (H_(cJ)) of their nitrides were 56 (for GA) and 2l7kA/m (for RDA). The H_(cJ) of nitrided Sm_2Fe_(17)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 practical value (600 kA/m) 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 grain size of quenched Sm_2Fe_(17) powder Consequently, high coercivity was obtained; the H_(cJ) of nitrided Sm_2Fe_(15)C_1Si_1 MS powder with Vs of 10 m/s was 898 kA/m, and 708 kA/m for the nitrided Sm_2Fe_(15)C_1Si_1 RDA powder The compression-molded bonded magnet made from Sm_2Fe_(18)Si_(0.1)N_x MS powder showed a high (BH)_(max) of 82.7 kJ/m~3.