INVESTIGATIONS ON THE MAGNETIC PROPERTIES AND MICROSTRUCTURES OF SINTERED NdFeB MAGNETS WITH DIFFERENT Nb ADDITIONS

The magnetic properties and microstructures of a series of sintered magnets Nd 33.0 Fe 65.9- x Nb x B 1.1 (wt%, x =0, 0.3 ,0.6,1.0,1.5,2.0) as well as their relations were investigated in detail. It was found that the grain size of NdFeB magnet without Nb addition was quiet different from each other and the shape of the grains was very irregular, which led to the deterioration of the magnetic properties. The microstructures of the magnets with proper Nb addition became homogeneous and the final size of the grain after annealing was very fine, and, correspondingly, the density of the final magnet was increased to a higher level. Magnetic measurements showed that the coercivity i\%H\-\%c, magnetic remanence B r and energy product ( BH) max of the magnet with Nb additions below 1.0wt% were generally higher than those of their Nb\|free counterparts. The effect of Nb on the magnetic properties originated mainly from the homogenization of the microstructure due to Nb addition.