Abstract: Since the rapid increase in rare earth prices, the demand for high-performance rare earth permanent magnets has increased, and manufacturers are accelerating the development of new processes. Rotating diffusion technology is especially suitable for mass production of small-sized magnets and Irregularly shaped magnets, and the appeal has good consistency in performance. Because of reutilization of heavy rare earth materials for diffusion, costs have been reduced.
In this paper, take one batch of magnets and set different parameters for experiments to seek the optimal process parameters, and identify the factors that have a significant impact on the results during the diffusion process.
（1）Mix the magnets, terbium sheets, and zirconia in a specific proportion, We obtained the optimal parameters of the rotating diffusion at 700℃ for six hours, following a two-stage annealing process at 920℃ for five hours and at 490 ℃ for four hours. Thus, the coercivity of the magnet could increase 11.59 kOe.
（2）SEM results show that most Tb enriches the surface of the magnets, and some Tb were diffused into the grain boundary phase, forming magnetic isolation during the rotating diffusion process. After the two-stage annealing process, many（Nd, Tb）₂Fe₁₄B substitutional phases with higher anisotropy field are formed around the epitaxial layer of the main phase increasing the coercivity of the magnet.
（3）Finally, we analyzed the surface changes of the Tb strip after multiple uses, and found that terbium tablets can reused three times. Enhance Coercivity of Sintered Nd-Fe-B Magnets by Rotating Diffusion.