Magnetic Properties of High Coercivity Melt-Spun Didymium-Fe-Co-Nb-V-B System Ribbons and their Bonded Magnets

Abstract

The melt-spun ribbons of Didymium-Fe-Co-Nb-V-B system alloys were prepared by single roller liquid rapid-quenching method. The effects of composition, wheel velocity and heat treatment on the magnetic properties were investigated. Didymium_12.5Fe_69.5Co₁₀Nb₁V₁B₆ ribbons prepared at a wheel velocity of 17.5 m/s were crystallized by heat treatment, and the optimum heat treatment condition was found to be at 600 °C for 5 min, then the values of (BH)_max and H_cJ were 128.3 kJ/m³, 1100.0 kA/m, respectively. The temperature coefficients of J_r and H_cJ for the ribbons crystallized from the Didymium_12.5Fe_69.5Co₁₀Nb₁V₁B₆ alloy were α(J_r)_ave=-0.044 %/°C(reversible) and α(H_cJ)=-0.370 %/°C(irreversible), respectively. The value of (BH)_max for the isotropic compression molding Didymium_12.5Fe_69.5Co₁₀Nb₁V₁B₆ bonded magnet prepared by using the ribbons annealed at 600 °C for 5 min is 88.9 kJ/m³ and the density is 6.3 Mg/m³. Irreversible loss of the bonded magnet is -3.64 %/°C(at 150 °C).