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<p>To enhance the high-temperature coercivity and thermal stability of sintered Nd-Fe-B magnets, this study employs low-melting-point Dy-Al eutectic alloys (Dy₉₅Al₅, Dy₉₀Al₁₀, Dy₈₅Al₁₅) as diffusion sources via magnetron sputtering and heat treatment. Systematic investigation reveals that the synergistic effect of Dy and Al is crucial for performance improvement, operating through dual mechanisms: “main-phase hardening” and “grain boundary optimisation.” Dy penetrates along optimised grain boundaries to form (Nd, Dy)₂Fe₁₄B core-shell structures on main-phase grains, hindering reverse domain nucleation. Simultaneously, Al improves the wettability and continuity of the grain boundary phase, enhancing intergranular decoupling and providing efficient channels for Dy diffusion. Among the investigated compositions, Dy₉₀Al₁₀ shows the best overall performance, which yields the highest coercivity increase from 13.39 kOe to 22.40 kOe (a 67.3% enhancement) and the best temperature stability within 300–390&#xa0;K (remanence temperature coefficient <i>α</i> = − 0.093%/K, coercivity temperature coefficient <i>β</i> = − 0.592%/K). Microstructural analysis confirms the formation of a uniform core-shell structure and continuous grain boundary phases at this composition. This work clarifies the appropriate Al content and the dual strengthening mechanism, providing a theoretical and practical foundation for developing high-performance, thermally stable Nd-Fe-B magnets with reduced heavy rare-earth consumption.</p>

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Effect of Dy-Al Grain Boundary Diffusion on the Properties and Microstructure of Sintered Nd-Fe-B Magnets

  • 期刊论文

  • 发表日期：

    2026年5月29日

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  • Jiandong Yang,
  • Zhiqiang Li,
  • Zhihao Dai,
  • Yusong Du,
  • Guangrui Zhang,
  • Jinxu Li

摘要

To enhance the high-temperature coercivity and thermal stability of sintered Nd-Fe-B magnets, this study employs low-melting-point Dy-Al eutectic alloys (Dy₉₅Al₅, Dy₉₀Al₁₀, Dy₈₅Al₁₅) as diffusion sources via magnetron sputtering and heat treatment. Systematic investigation reveals that the synergistic effect of Dy and Al is crucial for performance improvement, operating through dual mechanisms: “main-phase hardening” and “grain boundary optimisation.” Dy penetrates along optimised grain boundaries to form (Nd, Dy)₂Fe₁₄B core-shell structures on main-phase grains, hindering reverse domain nucleation. Simultaneously, Al improves the wettability and continuity of the grain boundary phase, enhancing intergranular decoupling and providing efficient channels for Dy diffusion. Among the investigated compositions, Dy₉₀Al₁₀ shows the best overall performance, which yields the highest coercivity increase from 13.39 kOe to 22.40 kOe (a 67.3% enhancement) and the best temperature stability within 300–390 K (remanence temperature coefficient α = − 0.093%/K, coercivity temperature coefficient β = − 0.592%/K). Microstructural analysis confirms the formation of a uniform core-shell structure and continuous grain boundary phases at this composition. This work clarifies the appropriate Al content and the dual strengthening mechanism, providing a theoretical and practical foundation for developing high-performance, thermally stable Nd-Fe-B magnets with reduced heavy rare-earth consumption.