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

Focusing on melt-spun ribbons of (Pr,Dy)15 (Fe,Co)77 (B,C)8 alloys prepared by the single roller method, the authors studied the effects of C substitution for B, Co for Fe and Dy for Pr in Pr15Fe77B8 alloy, and of the substrate surface velocity and subsequent annealing, on the ribbon magnetic properties. In addition, bonded magnets were fabricated from ribbons formed by quenching under optimum conditions. 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, it was confirmed that the highest maximum energy product, 96.4 kJ/m³, was obtained for (Pr0.95Dy0.05)15 (Fe0.9Co0.1)77(B0.5C0.5)8 alloy, which contains Dy and Co to improve the temperature dependence of Br and HCB. 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 bonded magnets of (Pr0.95Dy0.05) 15(Fe0.9Co0.1)77(B0.5C0.5)8 were (BH)max=64.9 kJ/m³, HCJ=1400 kA/m, HCB=419 kA/m, and Br=0.62 T. It was found that the temperature dependences of the Br and HCB of (Pr,Dy)-(Fe,Co)-(B,C) bonded magnets are superior to those of Pr-Fe-B bonded magnets.