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/sub 12.5/Fe/sub 68/ Co/sub 10/ Nb/sub 1/V/sub 1/Tb/sub 0.5/B/sub 7/ 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/spl deg/C for 5 min. The values of (BH)/sub max/ and H/sub cJ/ amount to 103.6 kJ/m/sup 3/ and 1628.0 kA/m, respectively. The temperature coefficients of J/sub r/ and H/sub cJ/ for the crystallized ribbons were /spl alpha/ (J/sub r/)/sub ave/=-0.03%//spl deg/C (reversible) and /spl alpha/ (H/sub cJ/)=-0.37%//spl deg/C (irreversible) for the temperature range 25 to 125/spl deg/C. The compression molded Didymium/sub 12.5/Fe/sub 68/Co/sub 10/Nb/sub 1/V/sub 1/Tb/sub 0.5/B/sub 7/ isotropic bonded magnet, prepared by using the ribbons annealed at 600/spl deg/C for 5 min, achieve the (BH)/sub max/ of 66.2 kJ/m/sup 3/. The density amounts to 6.32 Mg/m/sup 3/. At 150/spl deg/C, irreversible losses of -2.5% result.