多主相(Nd,Ce)-Fe-B磁体较同成分单主相磁体具有更高的磁性能，有望推动高丰度稀土Ce在永磁材料中的大量应用。然而，高Ce含量磁体的矫顽力离实际应用要求(≥12 kOe)仍有较大差距。本项目在保持多主相磁体晶粒间静磁耦合和消除交换耦合理论基础上，提出进一步细化晶粒减少反磁化畴形核中心，提高(Nd,Ce)-Fe-B矫顽力。拟通过Pr/Nd配合物有机溶剂包覆球磨制备亚微米超细磁粉，湿压成型控氧，实现晶粒尺寸小于3 μm的多主相磁体制备。系统研究烧结过程中不同成分主相的晶粒长大、元素互扩散及晶界结构的演变规律，阐明其理化反应过程和调控机理。并在此基础上，深入研究细化晶粒对多主相磁体磁畴结构和反磁化动态过程的影响，揭示细晶磁体中主相间的多尺度磁耦合规律，深化对细晶多主相磁体矫顽力机制的认识，为发展高性能低成本永磁材料奠定理论基础。

Multi-main phase (Nd,Ce)-Fe-B magnet was thought to be the most potential candidate with strategic and economic values among the permanent magnets family. However, high-Ce-content magnet exhibits decreased magnetic properties, especially the coercivity, which can not even satisfy the basic applications (≥12 kOe). Based on the rules of remaining the long-ranged magnetostatic interactions and suppressing the short-ranged exchange coupling interactions among the grains of multi-main-phase (MMP) magnets, present research is proposed to fabricate high-Ce-content (Nd,Ce)-Fe-B magnet with improved coercivity by refining the grain size. The submicron particles will be prepared by high energy ball-milling with Pr/Nd-containing organic solvent, and further wet-compress molding will be applied to prevent the oxidation of ultra-fine particles. Fine-grain-sized (less than 3 μm ) (Nd,Ce)-Fe-B MMP magnet will be obtained by subsequent sintering and annealing process. The local chemistry changes as well as structure fluctuates of fine-grained magnets on magnetic reversal process will be characterized and studied. Based on the results, the mechanism of grain growth, rare earth interdiffusions and multi-scaled magnetic coupling effects within the fine-grained MMP magnets will be characterized and discussed. The correlations between the local structure changes and coercivity will be established. This work is promising to obtain high-Ce-content and high-coercivity (Nd,Ce)-Fe-B magnets, which is of great significance from both the scientific and economic point of view.