Magnetic Properties of Low Rare-Earth Composition Pr-Fe-Co-Ti-Nb-Y-B System Melt-Spun Ribbons and Their Bonded Magnets

Abstract

Melt-spun ribbons made from low-rare-earth Pr-Fe-Co-Ti-Nb-Y-B system alloys were prepared by thesingle-roller rapid-quenching method, and the effects of composition, wheel velocity, and heat-treatment on their magnetic properties were investigated. It was found that the coercivity in Pr_3.5Fe_79-xCo₈Ti_1.5Nb₁Y_xB₇ ribbon increases with the amount of Y. In Pr_3.5Fe_78.5Co₈Ti_1.5Nb₁Y_0.5B₇ alloy ribbons, the magnetic properties were obtained (BH)_max = 109.6 kJ/m³, J_r = 1.29 T, H_cJ = 249.6 kA/m, and H_cB = 209.6 kA/m. The temperature coefficients of J_r and H_cJ of Pr_3.5Fe₇₈Co₈Ti_1.5Nb₁Y₁B₇ alloy ribbons were α(J_r)_ave = − 0.038%/°C and α(H_cJ) = − 0.390%/°C, respectively. The irreversible loss of an isotropic compression molding Pr_3.5Fe_78.5Co₈Ti_1.5Nb₁Y_0.5B₇ bonded magnet prepared by usingribbons annealed at 675°C for 5 min is −2.0% at 75°C, and this value was almost the same as that for an alnico bonded magnet.