Tailoring the diffusion depth and microstructure of RE-Fe-B magnets by low-pressure grain boundary diffusion process

A novel grain boundary A novel grain boundary diffusion process (GBDP) with low-pressure technology was employed to develop RE-Fe-B sintered magnets with a thickness of 2 mm. The gas pressure promotes Tb atoms to permeate the deeper of the magnets due to the uniform and continuous RE-rich phase, increasing the diffusion depth from 345 mu m to 880 mu m. According to the results acquired by computation, diffusion coefficients (D) of vacuum grain boundary diffusion process (VGBDP) and low-pressure grain boundary diffusion process (LPGBDP) rose from 2.27 x 10(-13) m2/s to 2.95 x 10(-12) m(2)/s, respectively. The increasing magnetocrystalline anisotropic field (122.2 kOe) and the optimized microstructure jointly determine the improvement of coercivity, which increases significantly from 17.47 kOe to 27.73 kOe by low-pressure diffusion treatment, 58.7% higher than the original magnet. Meanwhile, the homogeneous grain boundary phase and the thicker Tb-shell were mainly responsible for the excellent temperature stability in 20 degrees C-200 degrees C. This work proposes a viable method for preparing the RE-Fe-B magnets with slight HREE and high comprehensive performance. (c) 2022 Published by Elsevier B.V.