摘要
目前对于烧结Nd-Fe-B磁体的研究主要集中于如何在不损害其高性能特性的前提下,尽量降低其生产成本。本文以低重稀土Pr-Dy-CuGa四元合金为扩散源,将扩散源薄片贴附在烧结钕铁硼磁体表面进行扩散热处理,分析晶界扩散对磁体显微结构和服役性能的影响。结果表明:在晶界扩散后,烧结钕铁硼磁体的矫顽力显著提升,剩磁和最大磁能积略微下降;合金扩散改善了磁体的显微特性,优化了晶界相分布,减少了晶粒边界的缺陷,提高了主相晶粒的磁晶各向异性场;扩散后磁体主相的晶面间距增大,取向度得到明显改善;扩散处理后平均矫顽力温度系数和剩磁温度系数都得到改善,磁体的高温稳定性有一定提升;扩散处理后的磁体腐蚀电压下降,而腐蚀电流相对增高,耐腐蚀性能变差。
Sintered Nd-Fe-B permanent magnet material has been successfully used in a variety of energy-efficient,small and reliable multi-functional permanent magnet devices because of its excellent hard magnetic properties,constant magnetic field and efficient energy conversion function.The ever-changing new energy and new equipment in the future will put forward higher demands on the functions of sintered Nd-Fe-B magnets.The research aim of sintered Nd-Fe-B magnets is mainly focused on how to minimize the preparation cost while maintaining the high performance of magnets,and how to design cost-effective magnet materials under the increasingly severe utilization rate of rare earth resources to obtain cost advantages.Since the emergence of Nd-Fe-B materials,researchers have never stopped their exploration of improving the comprehensive performance of sintered Nd-Fe-B magnets,and optimized and innovated the preparation process.In recent years,grain boundary diffusion technology is often used to add heavy rare earth alloys to improve the properties of magnets and modify their microstructure.At present,the most studied method is to coat the alloy diffusion source on the surface of magnets,and then conduct heat treatment to diffuse the diffusion source into the magnets,so as to achieve the grain boundary modification.Grain boundary diffusion can effectively regulate the amount of heavy rare earth,so that the heavy rare earth is covered on the surface of the main phase grain in a gradient distribution to avoid excessive enrichment,and the distribution and continuity of the grain boundary phase are optimized on the microscopic level,which can enhance the coercivity without significant reduction of remanence.Nowadays,the research on sintered Nd-Fe-B magnets mainly focuses on how to reduce the production cost as far as possible without damaging their high-performance characteristics.In this work,a quaternary low-weight rare-earth alloy of Pr-Dy-Cu-Ga was used as the diffusion source to prepare the grain boundary diffusion sintered Nd-Fe-B magnets by attaching a thin Pr-Dy-Cu-Ga source sheet to the surface of the sintered magnets for the diffusing heat treatment.The influence of the grain boundary diffusion on the microstructure and service performance of the magnets was analyzed.It was shown that the coercivity of the sintered Nd-Fe-B magnets increased significantly after the grain boundary diffusion,while the remanence and the maximum magnetic energy product decreased slightly.The alloy diffusion improved the microscopic properties of the magnets,optimized the grain boundary phase distribution,reduced the grain boundary defects,and increased the magnetocrystalline anisotropy field of the main phase grains.After the diffusion treatment,the crystal surface spacing and the lattice parameters of the main magnet increased,the orientation degree was obviously improved,the average temperature coefficients of the coercivity and the remanence were both meliorated,and the high-temperature stability of the magnets was improved to a certain extent.Additionally,the obtained magnets presented a decreased corrosion voltage and an increased corrosion current,which indicated that the corrosion resistance of the magnets was deteriorated.The effect of grain boundary diffusion Pr-Dy-Cu-Ga alloy on the magnetic properties of sintered Nd-Fe-B magnets had been studied,and the microstructure,X-ray diffraction phase analysis and service properties of the sintered Nd-Fe-B magnets had been compared with non-diffusion samples.When the heat treatment process was 800℃×6 h+490℃×3 h,the comprehensive performance of the magnet of grain boundary diffusion (Pr_(75)Dy_(25))_(70)Cu_(15)Ga_(15) alloy was better,which was because the addition of more low melting point Pr elements could modify the microstructure of the magnet,minimize the defect at the grain boundary,and make Nd-rich phase more evenly distributed.A continuous thin strip was formed around the main grain,which better inhibited the direct contact of the main grain,made the size of the main grain smaller and the number of the main grain greater,the grain boundary became clear and smooth,and (Nd,Pr,Dy)_(2)Fe_(14)B shell was formed,which enhanced the anisotropy field of the grain boundary.(Pr_(75)Dy_(25))_(70)Cu_(15)Ga_(15) alloy diffusion magnet had higher grain orientation,because Pr element replaced Dy element to enter the main phase after diffusion,the crystal plane spacing of the main phase increased.Compared with the original sample,(Pr_(75)Dy_(25))_(70)Cu_(15)Ga_(15) alloy diffusion magnet temperature coefficients of remanence and coercivity increased,which indicated that the temperature stability of the diffusion sample had been improved.However,adding the low melting point element Pr,the volume of Nd-rich phase at the grain boundary had increased,which resulted in greater influence of sample corrosion after diffusion.In short,studying on the grain boundary diffusion of heavy rare earth with low melting point,the design process of diffusion source was optimized,and Pr-Dy-Cu-Ga four-element alloy diffusion source was prepared by replacing heavy rare earth element Dy with some light rare earth elementPr.The sintered Nd-Fe-B magnet with excellent properties was obtained on the basis of optimizing the utilization rate of rare earth resources and reducing the production cost.
作者
马利国
孙艳荣
张志鹏
李琬
李永贤
韩广豪
肖大庆
李冬至
Ma Liguo;Sun Yanrong;Zhang Zhipeng;Li Wan;Li Yongxian;Han Guanghao;Xiao Daqing;Li Dongzhi(Hebei Key Laboratory of Thermal Protection Materials,School of Materials Engineering,North China Institute of Aerospace Engineering,Langfang 065000,China;Zhongci Magnet Co.,Ltd.,Langfang 065000,China)
出处
《稀有金属》
北大核心
2025年第1期80-90,共11页
Chinese Journal of Rare Metals
基金
河北省省级科技计划-中央引导地方科技发展项目(216Z1005G)
河北省高等学校科学技术研究项目(QN2021001)
北华航天工业学院研究生创新项目(YKY-2024-58)资助。
关键词
烧结钕铁硼
晶界扩散
低重稀土合金
矫顽力
服役性能
sintered Nd-Fe-B magnets
grain boundary diffusion
low weight rare-earth alloy
coercivity
service performanc
作者简介
马利国(1974-),男,河北怀来人,博士,副研究员,研究方向:化工材料,E-mail:39814807@qq.com;通信作者:孙艳荣,教授,电话:18730602505,E-mail:809695720@qq.com。
