The invention provides a
grain boundary diffusion neodymium iron
boron magnet and a preparation method thereof, and relates to the technical field of magnetic materials. The preparation method comprises the steps of surface pretreatment and purification, precise
diffusion source construction through magnetron
sputtering and
diffusion promotion through vacuum heat treatment. The
core function of pretreatment is to remove surface impurities and lay a foundation for subsequent deposition of
alloy films; the proportion of Tb, Al and Cu in a diffusion source is accurately regulated and controlled in the magnetron
sputtering stage, and the synergistic effect is achieved; and the vacuum heat treatment promotes Tb to diffuse into the
neodymium iron
boron. According to the method, a technical
closed loop with pretreatment as a basis, a diffusion source as a core and heat treatment as power is formed, the
microstructure of the
neodymium-iron-
boron magnet is optimized, a complete and continuous shell structure with the moderate thickness is formed, the diffusion depth of heavy
rare earth is greatly increased, and the service life of the neodymium-iron-boron
magnet is prolonged. Finally, the coercive force of the neodymium-iron-boron magnet is remarkably improved, and the
utilization rate of heavy
rare earth elements is effectively improved. The problem of low Tb
utilization rate in the prior art is solved, and the
bottleneck of coercive force improvement is broken through.