高温下晶界扩散钕铁硼组织行为及矫顽力  

Microstructure behavior of grain boundary diffused Nd-Fe-B magnet and coercivity

作　　者：刘涛[1,2,3] 李建 邓志伟[2,3] 张守华 喻晓军[2,3] 李波 胡季帆[4] LIU Tao;LI Jian;DENG Zhiwei;ZHANG Shouhua;YU Xiaojun;LI Bo;HU Jifan(Central Iron and Steel Research Inst让ute,Beijing 100081,China;Advanced Technology and Materials Co.,Ltd.,Beijing 101318,China;School of Physics,Shandong University,Jinan 250100,Shandong,China;AT&M Magco Technology Co.,Ltd.,Zibo 255022,Shandong,China)

机构地区：[1]钢铁研究总院,北京100081 [2]安泰科技股份有限公司,北京101318 [3]安泰爱科科技有限公司,山东济南250100 [4]山东大学物理学院,山东淄博255022

出　　处：《金属功能材料》2022年第3期107-112,共6页Metallic Functional Materials

基　　金：安泰科技公司技术创新项目(2019JC0001ZCGN)。

摘　　要：钕铁硼晶界扩散技术已成为制备超高矫顽力烧结钕铁硼产品的必备技术,但是重稀土扩散源提升磁体矫顽力的行为及机制有诸多问题需要研究。利用高温激光扫描共聚焦金相显微镜(LSCM)对已经进行过晶界扩散的钕铁硼磁体重新进行高温加热和冷却,结合扫描电镜、电子探针、脉冲场磁强计观察初始状态、加热过程、冷却后的磁性能、微观组织行为及特征对比,结果发现:晶界扩散磁体进行过LSCM高温加热观测再经过冷却后,矫顽力下降636 kA/m,剩磁也进一步下降0.014 T,经过热处理后矫顽力未能完全恢复;LSCM高温加热实验发现,晶界扩散磁体加热过程中,在600~700℃范围内先后出现灰色和黑色的斑点并逐步扩展覆盖整体表面;冷却后样品表面被Nd、Dy、Al、Cu为主的膜层覆盖,说明加热过程中的斑点扩展是液相熔化后溢出表面并覆盖表面形成膜层的推论性解释;LSCM实验前后元素面分布图对比表明,高温加热后即便晶界和Dy分布显得连续,但因为高温加热破坏原有结构,矫顽力较低;重稀土在晶界附近的偏聚及高温下的相变诱导了主相周围形成高各向异性的(Nd,Dy)_(2)Fe_(14)B壳层,是晶界扩散提升矫顽力的核心原因。Nd-Fe-B grain boundary diffusion technology has become a crucial technology for ultra-high coercivity Nd-Fe-B sintered magnets.However,the heavy rare earth diffusion source behavior and mechanism related to the coercivity are still remain mysterious.High temperature laser scanning confocal microscope(LSCM)was used to heat and cool the grain boundary diffusion NdFeB magnet.Combined with SEM,electron probe microscopy and pulsed field magnetometer,microstructure behavior and characteristics of the initial state,heating process,magnetic properties after cooling were observed.The results showed that after heating and cooling,the coercivity decreased by 636 kA/m and the remanence further decreased by 0.014 T;LSCM high temperature heating experiment shows that gray and black spots appear successively in the range of 600-700℃during the heating process of grain boundary diffusion magnet,and gradually expand to cover the whole surface;After cooling,the surface of the sample is covered with a film mainly contains Nd,Dy,Al and Cu,indicating that the film is likely to be the intergranular Nd-rich phase,and spot expansion during the heating corresponds to the overflowing behavior of melted liquid Nd-rich phase;The comparison reslut of EPMA mapping before and after LSCM experiment shows that even if the grain boundary and Dy distribution appear continuous after heating and cooling,the coercivity is low because the original structure is destroyed by heating;The segregation of heavy rare earth near the grain boundary and the formation of high anisotropic(Nd,Dy)_(2)Fe_(14)B shell surrounding the main phase induced by the high temperature phase transformation is the core reason for the increase of coercivity in grain boundary diffusion process.

关 键 词：烧结钕铁硼 晶界扩散 矫顽力 高温加热观测 

分 类 号：TM273[一般工业技术—材料科学与工程]