Properties of terbium-doped (Nd,Dy)-(Fe,Co)-B sintered magnets

The microstructure of terbium (Nd,Dy)-(Fe,Co)-B sintered magnets has been investigated using optical microscopy, scanning electron microscopy, energy dispersive analytical X-ray microscopy and domain structures. The microstructure was found to be similar to that of an Nd-(Fe,Co)-B sintered magnet. The replacement of Nd by terbium in this system increases the coercivity and reduces the remanence. The increase of the coercivity of alloys lowers the irreversible losses at elevated temperature. The temperature coefficients of magnetic properties have also been improved through Tb substitution. Partial substitution of Dy by Tb does not influence the corrosion behaviour of the magnets. The corrosion tests confirm that addition of Co exhibits an advantageous effect on corrosion behaviour of the sintered RE-Fe-B magnets. (orig.)