基于磁控溅射工艺的晶界扩散对不同晶粒尺寸烧结钕铁硼磁体组织性能的影响研究

Study on the Effect of Magnetron Sputtering-Based Grain Boundary Diffusion on Microstructure and Properties of S-NdFeB Magnets with Varying Grain Sizes

摘要: 通过气流磨制备出不同粒径的钕铁硼磁粉，经相同的制备工艺及晶界扩散工艺形成晶界扩散磁体，经实验分析，研究了不同晶粒尺寸烧结NdFeB磁体经Tb晶界扩散改性后的组织演变、磁性能及力学性能变化规律，明确了兼顾高矫顽力、高剩磁与重稀土利用率的最优晶粒尺寸区间，结果表明：原始粉末粒径对烧结磁体的微观结构与密度起决定性作用。粉末粒径越小，烧结驱动力越大，磁体晶粒越细、密度越高；细晶磁体扩散后边界结构优化增益小、剩磁损失大，粗晶磁体基体性能差、优化后仍不理想，因此理想晶粒尺寸为6.5~7.0 μm，该区间磁性能与扩散源利用率均较高；晶界扩散能有效提升磁体抗弯强度，且细晶磁体因晶界相强化作用更显著而增益更大，粗晶磁体则以穿晶断裂为主、扩散效果较差，故强度提升不明显。

Abstract: NdFeB magnetic powders with different particle sizes were prepared by jet milling, and grain boundary diffusion magnets were formed through the same preparation process and grain boundary diffusion process. Through experimental analysis, the evolution of microstructure, magnetic properties, and mechanical properties of sintered NdFeB magnets with different grain sizes modified by Tb grain boundary diffusion was investigated, and the optimal grain size range that balances high coercivity, high remanence, and heavy rare earth utilization efficiency was determined. The results show that the original powder particle size plays a decisive role in the microstructure and density of the sintered magnet. The smaller the powder particle size, the greater the sintering driving force, resulting in finer grain size and higher density of the magnet. After diffusion, fine-grained magnets exhibit limited marginal benefit in boundary structure optimization but significant remanence loss, while coarse-grained magnets possess poor intrinsic magnetic properties and remain unsatisfactory even after optimization. Therefore, the ideal grain size range is 6.5~7.0 μm, within which both magnetic properties and diffusion source utilization efficiency are high. Grain boundary diffusion can effectively enhance the flexural strength of magnets, and fine-grained magnets show greater improvement due to more significant grain boundary phase strengthening, whereas coarse-grained magnets, dominated by transgranular fracture with poor diffusion effect, exhibit limited strength enhancement.