Magnetic hardening of melt-spun nanocomposite Nd\u3csub\u3e2\u3c/sub\u3eFe\u3csub\u3e14\u3c/sub\u3eB/Fe magnets

摘要

Coercivity optimization studies were done on melt-spun nanocomposite Nd4R2Fe87-xNbTxB6 (R=Nd,Y,Dy; T=Ag,Cu) isotropic ribbon samples. The maximum attainable coercivities, after adjusting the annealing time, were found to be very sensitive to the annealing temperatures. The optimum magnetic properties [Hc=3.9 kOe, (BH) max=10 MGOe] were obtained by annealing at 750–775 °C for a few minutes. Optimization by flash annealing gave similar results. Microstructural studies show that the grain size is greater than the theoretically predicted grain size for optimum coupling between the hard and the soft phase. With the annealing conditions used, Nd4Dy2Fe87NbB6 samples gave moderate coercivities and in Nd4Dy2Fe87NbB6 samples the coercivity was reduced more than the expected reduction in the anisotropy field due to the presence of Y.