Abstract:In this paper, high-performance sintered Nd-Fe-B magnets were prepared by grain boundary diffusion process. The effects of different Dy contents (0~2 %) on the post-diffusion magnetic properties and temperature stability of the magnets were studied. Scanning electron microscopy and X-ray diffraction analysis showed that after grain boundary diffusion, the heavy rare earth element Dy entered the main phase of the matrix, forming a "core-shell" structure. The edges of the main phase were converted from Nd2Fe14B phase to the higher magnetic anisotropy field (Nd, Dy)2Fe14B hard magnetic phase. After grain boundary diffusion, the coercivity of magnets with different Dy contents in the substrate increased to different degrees. The magnets without Dy had the largest increase in coercivity, with an increment of 7.05 kOe, while the magnets with 2.0 % Dy had the smallest increase in coercivity, only increasing by 5.30 kOe. With higher Dy content the less Dy element enters the magnet interior, the smaller the coercivity increase, and the lower the diffusion efficiency. The temperature stability of coercivity of the magnets after grain boundary diffusion was strengthened, and the temperature coefficient of coercivity was improved. The temperature coefficient of coercivity of the magnets with 2.0 % Dy in the substrate was the largest in the 20~120 ℃ range, reaching -0.52%/℃.