Magnetic properties of high quality melt-spun didymium-iron-cobalt-boron ribbons and their bonded magnets

Melt-spun ribbons of didymium-Fe-Co-B system alloys were prepared by the single-roller rapid-quenching method. The effects of composition, substrate surface velocity, and heat treatment on the magnetic properties were studied. The magnetic properties of isotropic compressed bonded magnets made of the optimum-annealing-condition ribbons were also measured. A maximum energy product of 149.1 kJ/m³ was obtained for 27 wt.% R-64.4 wt.% Fe-7 wt.% Co-1.6 wt.% B(R=Didymium) alloy ribbon prepared at a substrate velocity of 17.1 m/s. The amorphous 27 wt.% R-64.4 wt.% Fe-7 wt.% Co-1.6 wt.% B ribbons prepared at a substrate surface velocity of 20.7 m/s were crystallized by annealing treatment, and the optimum annealing condition was found to be at 650°C for 20 min. Its corresponding value of (BH)_max was 134.2 kJ/m³. The value of (BH)_max for the 27 wt.% R-64.4 wt.% Fe-7 wt.% Co-B bonded magnet prepared by using the ribbons annealed at 650°C for 20 min was 88.2 kJ/m³