富镧铈RE-Fe-B永磁稀土元素非均质分布与磁性能调控研究

增加钕铁硼永磁中高丰度稀土La、Ce的用量是提高其性价比的有效措施，但在提高丰量稀土含量的同时保持高的磁性能是目前面临的主要难题。本项目提出通过调控稀土元素在硬磁主相和晶界相中的分布来改善镧铈RE-Fe-B磁体的磁性能。在理解稀土元素非均质分布和磁体中相分离行为的基础上，通过成分优化，获得Nd/Pr在晶内富集、La/Ce在晶界富集的微观结构，在含较高丰量稀土磁体中获得高的磁性能。项目通过研究La/Ce含量、稀土总量和La/Ce比率对主相和晶界相稀土元素分布与磁特性的影响，探讨磁体成分、稀土元素分布与磁性能之间的关系；通过微观表征分析导致相分离的稀土元素分布特征，结合微磁学模拟阐释矫顽力突增机理；利用穆斯堡尔谱分析晶界相的特性，理解La、Ce对晶界的影响。最终实现稀土元素在磁体中的最优配置，提高La、Ce元素用量，并利用相分离和晶界优化提高矫顽力，为高性能低成本磁体的制备提供理论和实践基础。

Increasing the content of high abundance rare earth elements (REEs) of La, Ce elements in the Nd-Fe-B magnets is an efficient way to improve its performance/cost ratio. However, how to maintain the excellent hard magnetic properties in these magnets is the main problem. This project proposes to improve the magnetic properties of La/Ce containing magnets by regulating the distributions of REEs in the hard magnetic main phase and in the grain boundary phases. Based on the understanding of the chemical heterogeneity of REEs and the behavior of phase separation, this project aims to obtain high magnetic performance in the Nd-Fe-B based magnets with a relatively high content of high abundance REEs by forming an optimized microstructure with Nd/Pr segregation in the grains and La/Ce segregation in the grain boundary. The effects of the La/Ce substitution, the total content of REEs, and the ratio of La/Ce on the distribution of REEs in the main phase and grain boundary phases, and on the magnetic properties will be systematically investigated. The relationships among the compositions, distribution of REEs, and magnetic properties will be clarified. The distribution of REEs leading to phase separation will be analyzed by microstructure characterizations, and the mechanism of abnormal coercivity enhancement will be studied by micromagnetic simulation. 57Fe Mössbauer spectroscopy will be employed to investigate the influences of La/Ce substitution on the magnetic characteristic of the grain boundary phases. Finally, the usage of La/Ce elements will be increased by optimizing the distribution of REEs in the magnets, and the coercivity of the magnets will be further enhanced by taking advantages of phase separation and grain boundary modification. This work will provide both theoretical and practical basis for fabricating permanent magnets with high performance and low cost.