DyF3/Dy2O3共扩散对烧结Nd-Ce-Fe-B磁体微观结构和磁性能的影响

doi:10.19976/j.cnki.43-1448/TF.2024106

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Abstract In this paper, DyF₃ and Dy₂O₃ powders were used as diffusion sources to prepare high Ce content (Pr,Nd)₂₀Ce₁₁Fe_bal(Cu,Ga,Zr)_1.0B_0.97 (mass fraction) sintered magnets. The effects of DyF₃/Dy₂O₃ co-diffusion on the magnetic properties and microstructure of the magnets were investigated using ultra-high coercivity permanent magnet pulsed field magnetometer, X-ray diffractometer, differential scanning calorimeter, and electron probe microanalyzer. The results show that after DyF₃/Dy₂O₃ diffusion, the coercivity increases from 913.01 kA/m to 1 237.78 kA/m, representing an enhancement of 324.77 kA/m (35.6%). Additionally, the thermal stability is improved as the temperature coefficient of coercivity increasing from -0.606 %/℃ to -0.567 %/℃ in 20-120 ℃. The variation in remanence is minimal, with a change of only -0.01 T. After diffusion, the surface layer of the magnet predominantly consisted of the tetragonal (Nd,Ce,Dy)₂Fe₁₄B primary phase, along with a small proportion of cubic RE-O-F secondary phase. In the DyF₃/Dy₂O₃ system, Dy₂O₃ reduces the decomposition temperature of DyF₃ (<600 ℃), thereby providing a driving force for the diffusion of Dy atoms. Dy diffusion depth in DyF₃/Dy₂O₃ co-diffusion reaches up to 800 μm, the content of Dy gradually decreases with the increase of diffusion depth. Enriched regions of Dy and F elements are observed in the surface layer (0-60 μm). Ce is primarily enriched in the 0-60 μm range and at the triangular grain boundaries inside the bulk of the magnet. At a depth of 50-400 μm from the surface, Dy elements form a continuous network-like (Nd,Ce,Dy)₂Fe₁₄B shell structure around the main phase grains, which can effectively enhance the magnetocrystalline anisotropy field at the main phase grain surfaces, suppress the nucleation of reverse magnetization domains at the grain surfaces, and consequently improve the coercivity.

Key words： sintered Nd-Ce-Fe-B magnet grain boundary diffusion co-diffusion coercivity core-shell structure

Received: 03 December 2024 Published: 15 April 2025

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HE Zhanpeng,LI Liya. Effects of DyF₃/Dy₂O₃ co-diffusion on the microstructure and magnetic properties of sintered Nd-Ce-Fe-B magnets[J]. Materials Science and Engineering of Powder Metallurgy, 2025, 30(2): 131-138.

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http://pmbjb.csu.edu.cn/EN/10.19976/j.cnki.43-1448/TF.2024106 OR http://pmbjb.csu.edu.cn/EN/Y2025/V30/I2/131

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