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

doi:10.1088/1674-1056/abddad

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: dingguangfei@nimte.ac.cn;gshuai@nimte.ac.cn

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

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