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

Abstract

Melt-spun ribbons of Didymium-Fe-Co-Nb-Y-B system alloys were prepared by the single-roller liquid rapid-quenching method. The effects of Y addition, wheel velocity, and heat treatment on the magnetic properties were investigated. The optimum preparation conditions of the compounds were as follows: composition Didymium_12.5Fe_69.8Co₁₀Nb₁Y_0.7B₆; wheel velocity 20.0 m/s; heat treatment 650°C for 10 min. Magnetic properties of this ribbon were (BH)_max = 126.4 kJ/m³ and HcJ = 1409.0 kA/m. The value of (BH)_max for the isotropic compression molding Didymium_12.5Fe_69.8Co₁₀Nb₁Y_0.7B₆ bonded magnet prepared by using the ribbons annealed at 650°C for 10 min was 66.3 kJ/m³ and the density was 6.1 Mg/m³. The irreversible loss of this bonded magnet was -3.58 % (at 150°C). It was found that the irreversible loss was improved by Y addition.