重稀土/非磁性过渡族金属共扩散钕铁硼磁体的矫顽力机理研究

钕铁硼永磁材料磁性能优异，应用广泛，是不可替代的关键功能材料。重稀土晶界扩散技术是目前制备高性能钕铁硼磁体的最有效方法。然而，常用扩散源熔点高、扩散效率低、扩散深度浅以及晶界相结构改性不充分，限制了扩散磁体的应用推广。本项目以重稀土/非磁性过渡族金属作为扩散源，以电泳沉积作为扩散方法，利用非磁性过渡族金属增强晶界反应活性、液相扩散距离深、共扩散协同促进等优点，在有效增强磁体“核-壳”结构特征的同时形成连续均匀非磁性晶界结构。系统研究重稀土和非磁性过渡族金属元素的分布规律、成相特点及共扩散行为，阐明扩散过程的热力学机制，构建扩散模型。从磁化曲线、动态磁畴结构等多维度表征扩散磁体的磁化行为，并结合有限元模拟磁体磁化反磁化过程，揭示扩散磁体的矫顽力增强机理。本项目为发展高性能钕铁硼扩散磁体的关键制备技术，推动稀土资源高效平衡利用提供理论指导。

Nd-Fe-B permanent magnets have excellent magnetic properties and are widely used, which becomes an irreplaceable key functional material. The grain boundary diffusion technology of heavy rare earth elements is the most effective method to prepare high-performance Nd-Fe-B magnets. However, the common diffusion sources with the high melting point, low diffusion efficiency, shallow diffusion depth and inadequate modification of grain boundary phase structure limit the application of diffused magnets. In this project, heavy rare earth/ non-magnetic transition metals are used as diffusion sources, and electrophoretic deposition method is used as the main diffusion method. Taking full advantage of the enhanced grain boundary reactivity of non-magnetic transition metals and the deep diffusion depth of the liquid-liquid phase, we can effectively enhance the core-shell structure of the diffused magnets and simultaneously form continuous and uniform non-magnetic grain boundary. We intensively studied the element distribution, phase formation and co-diffusion behavior of the heavy rare earth and non-magnetic transition metal elements, clarified the thermodynamic mechanism of diffusion process, and constructed the diffusion model. Through the magnetization curve and dynamic domain structure to characterize the magnetization behavior of diffused magnets, and simulated the magnetization reversal process of the diffused magnets using the finite element method, therefore revealed the coercivity enhancement mechanism. This project provides theoretical guidance for the development of key preparation technology of high-performance diffused Nd-Fe-B magnets and the promotion of efficient and balanced utilization of rare earth resources.