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Chin. Phys. B, 2021, Vol. 30(6): 067503    DOI: 10.1088/1674-1056/abddad

Effects of post-sinter annealing on microstructure and magnetic properties of Nd-Fe-B sintered magnets with Nd-Ga intergranular addition

Jin-Hao Zhu(朱金豪)1,2, Lei Jin(金磊)1, Zhe-Huan Jin(金哲欢)1, Guang-Fei Ding(丁广飞)1,†, Bo Zheng(郑波)1, Shuai Guo(郭帅)1,2,‡, Ren-Jie Chen(陈仁杰)1,2, and A-Ru Yan(闫阿儒)1,2
1 CAS Key Laboratory of Magnetic Materials and Devices, and Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences(CAS), Ningbo 315201, China;
2 University of Chinese Academy of Sciences, Beijing 100049, China
Abstract  We investigate the effects of post-sinter annealing on the microstructure and magnetic properties in B-lean Nd-Fe-B sintered magnets with different quantities of Nd-Ga intergranular additions. The magnet with fewer Nd-Ga additions can enhance 0.2 T in coercivity, with its remanences nearly unchanged after annealing. With the further increase of the Nd-Ga addition, the annealing process leads coercivity to increase 0.4 T, accompanied by a slight decrease of remanence. With the Nd-Ga addition further increasing and after annealing, however, the increase of coercivity is basically constant and the change of remanence is reduced. Microstructure observation indicates that the matrix grains are covered by continuous thin grain boundary phase in the magnets with an appropriate Nd-Ga concentration after the annealing process. However, the exceeding Nd-Ga addition brings out notable segregation of grain boundary phase, and prior formation of part RE6Fe13Ga phase in the sintered magnet. This prior formation results in a weaker change of remanence after the annealing process. Therefore, the diverse changes of magnetic properties with different Nd-Ga concentrations are based on the respective evolution of grain boundary after the annealing process.
Keywords:  Nd-Fe-B magnet      magnetic properties      grain boundary      microstructures  
Received:  07 December 2020      Revised:  15 January 2021      Accepted manuscript online:  20 January 2021
PACS:  75.60.Nt (Magnetic annealing and temperature-hysteresis effects)  
  75.50.Ww (Permanent magnets)  
  75.50.Vv (High coercivity materials)  
  75.60.Ej (Magnetization curves, hysteresis, Barkhausen and related effects)  
Fund: Project supported by the Major Project of Science and Technology Innovation 2025 in Ningbo, China (Grant No. 2018B10086), the Major Project of Inner Mongolia Science and Technology, Zhejiang Provincial Public Welfare Technology Application Research Project, China (Grant No. LGG21E010007), and the Key Research and Development Program of Shandong Province, China (Grant No. 2019JZZY010321).
Corresponding Authors:  Guang-Fei Ding, Shuai Guo     E-mail:;

Cite this article: 

Jin-Hao Zhu(朱金豪), Lei Jin(金磊), Zhe-Huan Jin(金哲欢), Guang-Fei Ding(丁广飞), Bo Zheng(郑波), Shuai Guo(郭帅), Ren-Jie Chen(陈仁杰), and A-Ru Yan(闫阿儒) Effects of post-sinter annealing on microstructure and magnetic properties of Nd-Fe-B sintered magnets with Nd-Ga intergranular addition 2021 Chin. Phys. B 30 067503

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