MICROSTRUCTURE AND MAGNETIC-PROPERTIES OF ZN-BONDED OR SN-BONDED SM2FE17NX MAGNETS

Hard magnetic Sm2Fe17Nx alloy powders with a coercivity of 5.6 kA/cm and a remanent polarization of 1 T, related to the density of 7.7 g/cm3, could be achieved by a combined heat treatment in hydrogen atmosphere and a successive nitrogenation. During nitrogenation SmFe3 and SmFe2 constituents decompose into SmN and alphaFe immediately. The density of die-pressed anisotropic Sm2Fe17Nx magnets containing 5 wt % Zn amounts to approximately 5 g/cm3 and increases to 5.25 g/cm3 for additions of 20 wt % Zn. After annealing at 390-degrees-C for 10 h, the remanent polarization of 0.66 T and the coercivity of 8.8 kA/cm result in a maximal energy density of 67 kJ/m3. Annealing at temperatures of approximately 420-degrees-C achieves additional alphaFe due to a decomposition of SM2Fe17Nx by Zn: SM2Fe17Nx+Zn-->Sm2FeZn2+alphaFe+N2. Additions of 10 wt % Sn result in a density of 4.6 g/cm3 of isostatically compacted magnets. The remanent polarization amounts to approximately 0.6 T, but the coercivity H(cj) of approximately 4 kA/cm is inferior to Zn-bonded SM2Fe17Nx magnets.