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<p>Sintered Nd-Fe-B magnets are critical for electric vehicles and wind power, but their insufficient coercivity limits high-temperature reliability. Conventional grain boundary diffusion (GBD) methods suffer from complex operations, poor scalability, or excessive heavy rare-earth (HRE) use. This study developed a simple, scalable dip-coating GBD strategy: A uniformly dispersed DyF<sub>3</sub>-alcohol suspension (via ultrasonic dispersion) was coated on N35 magnets (initial coercivity <i>H</i><sub>cj</sub> = 11.83&#xa0;kOe), followed by vacuum heat treatment. Under optimized conditions (900℃/7&#xa0;h diffusion + 570℃/3&#xa0;h tempering), <i>H</i><sub>cj</sub> increased 26.97% to 15.02&#xa0;kOe&#xa0;(close to commercial 42&#xa0;M-grade), with only 1.48% remanence (<i>B</i><sub><i>r</i></sub>) loss—outperforming many Dy-based GBD processes for N35. XRD, BSE-SEM, and EDS showed Dy-substituted Nd to form high-anisotropy (Nd, Dy)<sub>2</sub>Fe<sub>14</sub>B, with continuous Dy-rich shells and uniform Nd-rich grain boundaries isolating main grains (suppressing reverse domains). Vickers hardness decreased (700 ± 10–630 ± 10&#xa0;HV) due to widened low-hardness grain boundaries. This work offers an industrially viable process&#xa0;for high-performance Nd-Fe-B magnets, enabling mass production for high-temperature applications.</p> Graphical Abstract <p>Addressing the instability of sintered Nd-Fe-B magnets in high-temperature operating environments, we adopted a dip-coating method and then grain boundary diffusion heat treatment. The coercivity of optimized magnet reaches 15.02 kOe from 11.83 kOe, obtaining a new technological path for the preparation of high performance Nd-Fe-B magnets.</p>

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Grain boundary diffusion of dysprosium using DyF3 dip-coating method to enhance the magnetic properties of sintered Nd-Fe-B magnet

  • 期刊论文

  • 发表日期：

    2025年12月3日

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  • Zechuan Wang,
  • Zhenyu Li,
  • Jian Li,
  • Jikun Deng,
  • Meng Li,
  • Guoqing Tong,
  • Honghai Zhong,
  • Junwu Liu,
  • Yang Jiang

摘要

Sintered Nd-Fe-B magnets are critical for electric vehicles and wind power, but their insufficient coercivity limits high-temperature reliability. Conventional grain boundary diffusion (GBD) methods suffer from complex operations, poor scalability, or excessive heavy rare-earth (HRE) use. This study developed a simple, scalable dip-coating GBD strategy: A uniformly dispersed DyF3-alcohol suspension (via ultrasonic dispersion) was coated on N35 magnets (initial coercivity Hcj = 11.83 kOe), followed by vacuum heat treatment. Under optimized conditions (900℃/7 h diffusion + 570℃/3 h tempering), Hcj increased 26.97% to 15.02 kOe (close to commercial 42 M-grade), with only 1.48% remanence (Br) loss—outperforming many Dy-based GBD processes for N35. XRD, BSE-SEM, and EDS showed Dy-substituted Nd to form high-anisotropy (Nd, Dy)2Fe14B, with continuous Dy-rich shells and uniform Nd-rich grain boundaries isolating main grains (suppressing reverse domains). Vickers hardness decreased (700 ± 10–630 ± 10 HV) due to widened low-hardness grain boundaries. This work offers an industrially viable process for high-performance Nd-Fe-B magnets, enabling mass production for high-temperature applications.

Graphical Abstract

Addressing the instability of sintered Nd-Fe-B magnets in high-temperature operating environments, we adopted a dip-coating method and then grain boundary diffusion heat treatment. The coercivity of optimized magnet reaches 15.02 kOe from 11.83 kOe, obtaining a new technological path for the preparation of high performance Nd-Fe-B magnets.