Magnetic properties of high coercivity melt-spun Didymium-Fe-Co-Nb-V-Tb-B system ribbons and their bonded magnets

The melt-spun ribbons of Didymium(12.5)Fe(68) Co-10 Nb1V1Tb0.5B7, prepared at a wheel velocity of 17.5 m/s were crystallized by heat treatment. The optimum heat treatment condition was found to be at 600 degrees C for 5 min. The values of (BH)(max) and H-cJ amount to 103.6 kJ/m(3) and 1628.0 kA/m, respectively. The temperature coefficients of J(r) and H-cJ for the crystallized ribbons were alpha (J(r))(ave) = -0.03%/degrees C (reversible) and alpha (H-cJ) = -0.37%/degrees C (irreversible) for the temperature range 25 to 125 degrees C. The compression molded Didymium(12.5) Fer(68) Co-10 Nb-1 V-1 Tb-0.5 B-7 isotropic bonded magnet, prepared by using the ribbons annealed at 600 degrees C for 5 min, achieve the (BH)(max) of 66.2 kJ/m(3). The density amounts to 6.32 Mg/m(3). At 150 degrees C, irreversible losses of -2.5 % result.