Extraordinary simultaneous enhancement of the coercivity and remanence of dual alloy HRE-free Nd-Fe-B sintered magnets by post-sinter annealing  

作　　者：Qingfang Huang Qingzheng Jiang Jifan Hu Sajjad Ur Rehman Gang Fu Qichen Quan Jixiang Huang Deqin Xu Dakun Chen Zhenchen Zhong 

机构地区：[1]Jiangxi Key Laboratory for Rare Earth Magnetic Materials and Devices&College of Rare Earths,Jiangxi University of Science and Technology,Ganzhou 341000,China [2]Fujian Key Laboratory for Rare Earth Functional Materials,Longyan 366300,China [3]School of Materials Science and Engineering,Taiyuan University of Science and Technology,Taiyuan 030024,China

出　　处：《Journal of Materials Science & Technology》2022年第11期236-242,共7页材料科学技术（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.51901089 and 52061015);the Key Research and Development Program of Jiangxi Province(No.20201BBE51010);China Postdoctoral Science foundation(Grant No.2020M682064);Postdoctoral Science foundation of Jiangxi Province(Grant No.2020KY19);the Program of Qingjiang Excellent Young Talents of Jiangxi University of Science and Technology(No.JXUSTQJYX2020003)。

摘　　要：Post-sinter annealing process plays an important role in the microstructures and magnetic properties of the Nd-Fe-B sintered magnets.In this paper,systematically investigated are the magnetic properties and microstructures of the as-sintered and post-sinter annealed Nd-Fe-B magnets with Pr-Fe-Ga boundary addition.Two choice consecutive annealing methods are adopted at high and low temperatures,namely the 1 st annealing at 880℃ for 2 h and then the 2^(nd) annealing at 440℃ for 3 h.It is exceptional to find out that both the remanence and coercivity are improved after 2^(nd) annealing process for this type of magnet.The coercivity is hugely increased from 10.09 kOe for the as-sintered sample to 17.19 kOe for the 2^(nd) annealed magnet,with a significant increment of 70.37%in coercivity.The extraordinary magnetic properties of B_(r)=14.44 kGs,H_(cj)=17.19 kOe and(BH)_(max)=51.08 MGOe are obtained for the designated Nd-Fe-B sintered magnets without heavy rare earth(HRE)elements manufactured by dual alloy method.The Curie temperature is monotonically decreased from 634 K to 602 K while the c-axis alignment degree is optimized after annealing.Microstructural observation and analysis indicate that the elemental distribution patterns are altered after the 2^(nd) annealing.The diffusion of the aggregate(Pr,Nd,Cu,Ga)-rich phase from triple junctions into the grain boundary regions is ascribed to the formation of thin and continuous grain boundary layer,which is critical to improve the microstructures and magnetic properties.

关 键 词：Nd-Fe-B sintered magnets HRE-free Dual alloy method Post-sinter annealing Magnetic properties 

分 类 号：TM273[一般工业技术—材料科学与工程]