摘要
以((La,Ce)_(0.2)(Pr,Nd)_(0.8))Fe_(bal)B商业高丰度磁体为原料,对其热扩散工艺进行研究。针对Ce、La含量较高、磁体热扩渗效果较差的问题,提出采用烧结态磁体直接进行热扩渗处理。研究表明:磁体的最佳热扩渗工艺参数为880℃×8 h+500℃×2 h,矫顽力从8.11 kOe直接提高到18.38 kOe,与时效后热扩渗磁体矫顽力相比增幅10.4%。晶粒尺寸相比时效后热扩渗磁体减少0.96μm,约14%。通过菲克第二定律计算,晶界中Dy元素对主相晶粒的扩散系数D_(1)=4.8×10^(-6)μm^(2)·s^(-1),D_(2)=1.1μm^(2)·s^(-1)。可见,Dy元素在高丰度稀土磁体中热扩渗相对较慢,形成(Nd/Ce/La/Dy)_(2)Fe_(14)B壳层需更长时间,但长时间热扩渗导致晶粒尺寸增加,含氧量增加,因此热扩渗效果较差。采用烧结态直接热扩渗工艺,合并时效和热扩渗工序,缩短工序流程,减少了磁体在高温处理的时间,避免了晶粒粗化,降低晶粒尺寸,可获得更好的微观组织结构,进而提升磁体矫顽力,对提高高丰度稀土永磁体矫顽力具有重要意义。
The thermal diffusion process of high-abundance permanent magnets((La,Ce)_(0.2)(Pr,Nd)_(0.8))Fe_(bal)B was investigated.Meanwhile,the thermal diffusion behavior of heavy rare earth was analyzed.The high-abundant magnets present a poor thermal diffusion effect because of the magnets with more Ce and La content.In order to solve this problem,a direct thermal diffusion process was proposed.The sintered magnets were directly performed thermal diffusion treatment.The optimal thermal diffusion process parameter is 880℃×8 h+500℃×2 h,and the coercivity is directly increased from 8.11 kOe to 18.38 kOe.Compared to the coercivity and grain size of magnet diffused after aging,the coercivity increases by 10.4%,and the average grain size is reduced about 14%,respectively.According to Ficks second law,the diffusion coefficients of Dy were calculated.The coefficients into the main phase grain and the grain boundary are D_(1)=4.8×10^(-6)μm^(2)·s^(-1),D_(2)=1.1μm^(2)·s^(-1),respectively.The thermal diffusion of Dy in the high-abundance rare earth magnet is slower than that of the ordinary magnet.It should take longer time to form(Nd/Ce/La/Dy)_(2)Fe_(14)B shell.The long-term thermal diffusion results in an increase of the grain size and oxygen content,this is the reason why the high-abundance magnets present a poor thermal diffusion effect.By using the direct thermal diffusion process,the aging and thermal diffusion processes can be combined.This process would shorten the time for the magnets during high-temperature treatment.Therefore,the grain size of the magnets could be reduced and the microstructure of the magnets would be improved,which result into enhancement of the magnet coercivity.Direct thermal diffusion process avoids grain coarsing and shortens the working process,so it is of great significance to improve the coercivity of high-abundance rare earth permanent magnets.
作者
高宇
刘治国
孙亚辉
张通博
徐大可
裴文利
GAO Yu;LIU Zhiguo;SUN Yahui;ZHANG Tongbo;XU Dake;PEI Wenli(School of Materials Science and Engineering,Northeastern University,Shenyang 110819,Liaoning,China;Qingdao Campus of Naval Aviation University,Qingdao 26604l,Shandong,China;Key Laboratory of Anisotropy and Texture of Materials,Ministry of Education,Northeastern University,Shenyang 110819,Liaoning,China)
出处
《金属功能材料》
CAS
2024年第2期64-72,共9页
Metallic Functional Materials
基金
国家重点研发计划(2021YFB3501404)
云南省重大科技专项-新材料重大专项(202102AB080008-1)
国家自然科学基金资助项目(523711795,52071070)。
关键词
高丰度稀土永磁体
扩散系数
直接扩渗法
矫顽力
重稀土扩散行为
high abundance rare earth permanent magnet
diffusion coefficient
direct diffusion method
coercivity
diffusion behaviorof heavy rareearths
