New kind of NdFeB magnet prepared by spark plasma sintering

We have produced an anisotropic Nd_15.5Dy_1.0Fe_72.7Co_3.0B_6.8Al_1.0 magnet by the spark plasma sintering (SPS) technique and compared it with a magnet of the same composition processed by the conventional sintering method. We investigated magnetic properties, microstructure, and constituents by a B-H loop-line instrument, a scanning electron microscope, and an energy-dispersive X-ray detector, and studied the effects of processing conditions on the magnetic properties, dimensional precision, and density. We also examined the magnet´s electrochemical properties in electrolytes and its corrosion behavior in oxidizing environments. We found that the microstructure of the SPS NdFeB magnet is different from that of the conventional one. In the SPS-processed magnet, the grain size is fine and uniform while the distribution of the Nd-rich phase is heterogeneous. The SPS NdFeB magnet has a maximum energy product of 240 kJ/m³ and a coercive force of 1260 kA/m. The density of the magnet reaches 7.58 g/cm³, and its dimensional precision is about 20 μm. The electrochemical properties and the corrosion resistance of the SPS NdFeB magnet are better than those of the conventional one. The SPS process is a promising method for the production of NdFeB magnets with ideal overall performance.