MAGNETIC HARDENING OF MELT-SPUN NANOCOMPOSITE ND2FE14B FE MAGNETS/

Coercivity optimization studies were done on melt-spun nanocomposite N d(4)R(2)Fe(87-x)NbT(x)B(6) (R=Nd,Y,Dy; T=Ag,Cu) isotropic ribbon sampl es. The maximum attainable coercivities, after adjusting the annealing time, were found to be very sensitive to the annealing temperatures. The optimum magnetic properties [H-c=3.9 kOe, (BH)(max)=10 MGOe] were obtained by annealing at 750-775 degrees C for a few minutes. Optimiza tion by flash annealing gave similar results. Microstructural studies show that the grain size is greater than the theoretically predicted g rain size for optimum coupling between the hard and the soft phase. Wi th the annealing conditions used, Nd4Dy2Fe87NbB6 samples gave moderate coercivities and in Nd4Y2Fe87NbB6 samples the coercivity was reduced more than the expected reduction in the anisotropy field due to the pr esence of Y. (C) 1996 American institute of Physics.