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

贺展鹏; 李丽娅

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

粉末冶金材料科学与工程 >

2025 , Vol. 30 >Issue 2: 131 - 138

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

工艺技术

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

贺展鹏 ,
李丽娅

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中南大学粉末冶金研究院, 长沙 410083

收稿日期: 2024-12-03

修回日期: 2025-02-26

网络出版日期: 2025-04-15

基金资助

湖南省自然科学基金资助项目(2020JJ4713)

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Effects of DyF₃/Dy₂O₃ co-diffusion on the microstructure and magnetic properties of sintered Nd-Ce-Fe-B magnets

HE Zhanpeng ,
LI Liya

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Powder Metallurgy Research Institute, Central South University, Changsha 410083, China

Received date: 2024-12-03

Revised date: 2025-02-26

Online published: 2025-04-15

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摘要

本文以DyF₃和Dy₂O₃粉末为扩散源,制备高Ce含量(Pr,Nd)₂₀Ce₁₁Fe_bal(Cu,Ga,Zr)_1.0B_0.97 (质量分数)烧结磁体,采用超高矫顽力永磁脉冲测量仪、X射线衍射仪、差示扫描量热仪和电子探针显微分析仪等,研究DyF₃/Dy₂O₃共扩散对磁体磁性能和微观结构的影响。结果表明：DyF₃/Dy₂O₃扩散后,磁体的矫顽力由913.01 kA/m提高至1 237.78 kA/m,提高了324.77 kA/m (35.6%);20~120 ℃的矫顽力温度系数由-0.606 %/℃提高至-0.567 %/℃,热稳定性增强;剩磁的变化量很小,仅为-0.01 T。扩散后磁体表层主要由四方结构(Nd,Ce,Dy)₂Fe₁₄B主相和少量立方结构RE-O-F第二相构成。DyF₃/Dy₂O₃体系中,Dy₂O₃使DyF₃的分解温度降低(<600 ℃),为Dy原子扩散提供了驱动力。DyF₃/Dy₂O₃共扩散时,Dy扩散深度可达800 μm,Dy含量随扩散深度的增加逐渐降低,在表层0~60 μm处出现Dy和F元素富集区,Ce主要富集于0~60 μm处和磁体内部的三角晶界处。在距离表面50~400 μm处,Dy元素在主相晶粒周围形成连续网络状(Nd,Ce,Dy)₂Fe₁₄B壳层结构,该结构可有效增强主相晶粒表面的磁晶各向异性场,抑制晶粒表面反磁化畴的形核,提高矫顽力。

关键词： 烧结Nd-Ce-Fe-B磁体; 晶界扩散; 共扩散; 矫顽力; 核壳结构

本文引用格式

贺展鹏 , 李丽娅 . 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[J]. 粉末冶金材料科学与工程, 2025 , 30(2) : 131 -138 . DOI: 10.19976/j.cnki.43-1448/TF.2024106

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

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