Magnetic Properties of Melt-Spun (Pr, Dy)-(Fe, Co)-(B, C) Alloys and Their Bonded Magnets

Abstract

In melt-spun ribbons of (Pr, Dy)₁₅(Fe, Co,)₇₇(B, C)₈ alloys prepared by the single roller method, the effects of C substitution for B, Co for Fe and Dy for Pr in Pr₁₅Fe₇₇B₈ alloy, substrate surface velocity and subsequent annealing on the magnetic properties were studied, and their bonded magnets were made of the optimum-quenched ribbons. The maximum energy product of 98.3 kJ/m³ was obtained for Pr₁₅Fe₇₇B₈ ribbon prepared at a substrate surface velocity of 11.8 m/s. In (Pr, Dy)₁₅(Fe, Co)₇₇(B, C)₈ ribbons, we confirmed that the best maximum energy product of 96.4 kJ/m³ was obtained for (Pr_0.95Dy_0.05)₁₅(Fe_0.9Co_0.1)₇₇(B_0.5C_0.5)₈ alloy which contains Dy and Co to improve the temperature dependence of B_r and H_CB. X-ray diffraction patterns from samples with the highest coercivity showed a mixture of an amorphous and a fine crystalline phase. The best magnetic properties obtained in these bonded magnets of (Pr_0.95Dy_0.05)₁₅(Fe_0.9Co_0.1)₇₇( B_0.5C_0.5)₈ alloy were (BH)_max=64.9 kJ/m₃, H_CJ=1400 kA/m, H_CB=419 kA/m, and B_r=0.62 T. It was known that the temperature dependence of B_r and H_CB for (Pr, Dy) -(Fe, Coi)-(B, C) bonded magnets was superior to those of Pr-Fe-B bonded magnets.