Abstract Nd-Fe-B based magnets exhibit excellent magnetic properties and are being widely used in high-technology, information, energy and medical fields, etc. Nowadays, with the rapid development of the electric vehicle industries, Nd-Fe-B magnets have also stepped into a period of rapid development. However, it brings a higher requirement for the magnetic properties at the same time, especially higher coercivity. It is found that the magnetic properties of Nd-Fe-B magnets are related to the components and microstructures of their intergranular phases. Adding some materials by the traditional smelting process can modify intergranular or matrix phases to increase the coercivity of the magnets. The additives evenly distributed in the matrix Nd2Fe14B phases may cause the original composition and structure of Nd2Fe14B phases to be partially destroyed. It also causes not only the remanence of the magnets to be decreased but also a large amount rare earth resources to be wasted. More excitingly, in 2005, a new technology is proposed, named as “Grain Boundary Diffusion”, which effectively increases the coercivity of Nd-Fe-B magnets with a small amount of rare earth additives. And the remanence is usually only slightly reduced. This technology is attributed to modify the composition and structure of grain boundary phases or Nd2Fe14B grains by different material diffusion. In this paper, the research achievements of grain boundary diffusion technologies so far will be introduced. It mainly focuses on the influence of additives on the interface between grain boundary phases and matrix Nd2Fe14B phases, as well as on the intrinsic connection between the microstructures and the magnetic properties. The corresponding diffusion mechanism is also summarized, which serves as data support for the further development of grain boundary diffusion technology.

中文翻译：

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晶界扩散工程对钕铁硼磁体微观结构和磁性能的改性研究进展

摘要 Nd-Fe-B基磁体具有优良的磁性能，被广泛应用于高科技、信息、能源和医疗等领域。也进入了高速发展期。但同时也对磁性能提出了更高的要求，尤其是矫顽力更高。研究发现，Nd-Fe-B磁体的磁性能与其晶间相的成分和微观结构有关。通过传统冶炼工艺添加一些材料可以改变晶间相或基体相，以增加磁体的矫顽力。均匀分布在基体 Nd2Fe14B 相中的添加剂可能会导致 Nd2Fe14B 相的原始成分和结构被部分破坏。不仅造成磁铁剩磁下降，而且浪费了大量的稀土资源。更令人振奋的是，2005年提出了一项名为“晶界扩散”的新技术，该技术在加入少量稀土添加剂的情况下，有效提高了Nd-Fe-B磁体的矫顽力。剩磁通常仅略微降低。该技术归因于通过不同的材料扩散来改变晶界相或 Nd2Fe14B 晶粒的组成和结构。本文将介绍目前晶界扩散技术的研究成果。主要关注添加剂对晶界相与基体Nd2Fe14B相界面的影响，以及显微组织与磁性能的内在联系。