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<p>This study presents a systematic approach to enhancing the coercivity, thermal stability, and corrosion resistance of sintered NdFeB magnets through optimized grain boundary diffusion (GBD) and multi-stage aging heat treatment. Conventional GBD strategies often suffer from inefficient Dy utilization, limited diffusion depth, and uneven distribution along grain boundaries, resulting in suboptimal magnetic performance and environmental durability. To address these challenges, this work employs a minimal amount of Dy and systematically varies diffusion temperatures and aging protocols to optimize intergranular diffusion behavior. Intrinsic coercivity (<sub>i</sub><i>H</i><sub>c</sub>) was elevated beyond 26 kOe, while high remanence (<i>B</i><sub>r</sub>) and a squareness ratio (<i>SQR</i> &gt; 0.94) were effectively maintained. Characterization via glow discharge optical emission spectroscopy (GDOES) and electron probe microanalysis (EPMA) confirmed uniform Dy enrichment along grain boundaries, which suppressed magnetic reversal and stabilized domain behavior. The antiferromagnetic Dy–Fe exchange interaction was identified as the principal mechanism governing the trade-off between coercivity enhancement and remanence suppression. The proposed process enables high-performance magnet fabrication with substantially reduced heavy rare earth consumption, offering a resource-efficient and scalable solution for electric drive systems, wind turbines, and other applications demanding thermal and magnetic stability.</p>

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Optimizing grain boundary diffusion and aging heat treatment for enhancing coercivity, thermal stability, and corrosion resistance in NdFeB permanent magnets

  • 期刊论文

  • 发表日期：

    2025年10月17日

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  • Chih-Chieh Mo,
  • Min-Wen Wang,
  • Shih-Fu Ou,
  • Ching-Chien Huang

摘要

This study presents a systematic approach to enhancing the coercivity, thermal stability, and corrosion resistance of sintered NdFeB magnets through optimized grain boundary diffusion (GBD) and multi-stage aging heat treatment. Conventional GBD strategies often suffer from inefficient Dy utilization, limited diffusion depth, and uneven distribution along grain boundaries, resulting in suboptimal magnetic performance and environmental durability. To address these challenges, this work employs a minimal amount of Dy and systematically varies diffusion temperatures and aging protocols to optimize intergranular diffusion behavior. Intrinsic coercivity (iHc) was elevated beyond 26 kOe, while high remanence (Br) and a squareness ratio (SQR > 0.94) were effectively maintained. Characterization via glow discharge optical emission spectroscopy (GDOES) and electron probe microanalysis (EPMA) confirmed uniform Dy enrichment along grain boundaries, which suppressed magnetic reversal and stabilized domain behavior. The antiferromagnetic Dy–Fe exchange interaction was identified as the principal mechanism governing the trade-off between coercivity enhancement and remanence suppression. The proposed process enables high-performance magnet fabrication with substantially reduced heavy rare earth consumption, offering a resource-efficient and scalable solution for electric drive systems, wind turbines, and other applications demanding thermal and magnetic stability.