感应涡流对扩散钕铁硼磁体的矫顽力增强机制研究

The project is to reconstruct the microstructure of the sintered Nd–Fe–B magnets, study the coercivity enhancement mechanism of the grain boundary diffusion processed Nd-Fe-B magnets by induction vortex treatment. Using electrophoretic deposition (EPD) method, the heavy rare earth compound was deposited onto the surface of the sintered Nd–Fe–B magnets. During the diffusion heat treatment process, the heavy rare earth elements diffused into the inside of the magnets. We clarified the quality of the coatings and the magnetic property changes of the magnets as a function of the key process parameters, analyzed the microstructural distribution and phase transition of the heavy rare earth after diffusing into the magnets, and revealed the thermodynamic mechanism of the diffusion of the heavy rare earth. To develop and improve the coercivity enhancement mechanism of the EPD-coated magnets, the influence of the local enrichment of heavy rare earth on the magneto-crystalline anisotropy field and the distribution of the grain boundary phase and the magnetic property were also studied. Though the strong electromagnetic stirring effect of the induction vortex heating, we can achieve the microstructural reconstruction of the grain boundary diffused Nd–Fe–B magnets. The effect of the key process parameters on the grain shape, orientation degree, grain boundary phase structure and the phase distribution were analyzed. We observed the magnetic domains by magneto-optical kerr microscope and lorentz electron microscopy to analyze the magnetization and the reversal magnetization behavior and clarify the coercivity enhancement mechanism of the magnets after microstructural reconstruction.The project is dedicated to developing new key preparation technology of rare earth permanent magnets and improving the existing magnetic mechanism of rare earth permanent magnets, which has the important theoretical significance and application value.

本项目以重构烧结钕铁硼磁体微观结构为出发点，研究感应涡流对扩散钕铁硼磁体的矫顽力增强机制。利用电泳沉积方法将重稀土化合物沉积到磁体表面，结合扩散热处理工艺使重稀土扩散到磁体内部。阐明关键工艺参数对涂层品质、磁体磁性能的影响规律，分析重稀土元素进入磁体后的微观分布特征、成相行为，揭示重稀土扩散的热力学机制。并探究重稀土局域性富集对磁晶各向异性场、晶界相分布和磁性的影响，发展和完善电泳沉积磁体的矫顽力增强机制。利用感应涡流加热的强烈电磁搅拌特性实现重稀土扩散钕铁硼磁体的微观组织重构。分析关键工艺参数对晶粒形状、取向度、晶界相结构和相分布的影响，综合利用磁光克尔显微镜、洛伦兹电镜等磁畴检测方法，分析微观结构重构后磁体的磁化和反磁化行为，阐明微观结构重构后磁体的矫顽力增强机制。本项目致力于发展新型稀土永磁材料关键制备技术，完善和发展现有的稀土永磁材料磁性机理，具有重要理论意义和应用价值。

近年来，电动车、风力发电、节能家电等领域对稀土永磁材料的需求日益增多，为了满足新兴领域的应用要求，促进稀土资源的高效利用，提高烧结钕铁硼永磁材料综合磁性能、减少高矫顽力磁体的重稀土用量已成为烧结钕铁硼研究领域的重要目标。.本工作创新性提出一种能够优化钕铁硼磁体微观结构、提升磁体矫顽力的感应涡流热处理工艺，阐明相关的微观结构优化机理和矫顽力增强机制。本工作发展了新型电泳沉积制备晶界扩散磁体方法，提出了低重稀土高矫顽力晶界扩散磁体的制备技术，详细研究了电泳沉积技术方法对磁体磁性能和微观结构的影响规律，阐明了磁体的矫顽力增强机制和重稀土的扩散机制，并分析了晶界扩散磁体的使役性能。.获得了制备无/低重稀土高矫顽力磁体制备技术。利用细化晶粒技术和感应涡流热处理技术，成功制备出了无重稀土高矫顽力磁体，磁体综合性能为Br = 13.2kGs，矫顽力Hcj = 20.5 kOe，磁能积(BH)max = 42.7 MGOe。利用电泳沉积技术，添加约1.43 wt.%的重稀土Tb含量，制备出具有高磁性能的晶界扩散磁体。磁体磁性能达到Br=13.84 kGs，(BH)max=46.10 MGOe，磁体矫顽力较扩散前增长约12.03kOe，达到Hcj=26.00 kOe。