首页|Thermal stability improvement and microstructure optimization of high cobalt content Nd-Fe-B magnets via terbium grain boundary diffusion

Thermal stability improvement and microstructure optimization of high cobalt content Nd-Fe-B magnets via terbium grain boundary diffusion

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The substitution of Fe by Co in the 2∶14∶1 phase is an effective method to increase the Curie temperature and enhance the thermal stability of the Nd-Fe-B magnets.However,the accumulation of Co element at the grain boundaries(GBs)changes the GBs from nonmagnetic to ferromagnetic and causes the thin-layer GBs to become rare.In this paper,the method of diffusing Tb element was chosen to improve the microstructure and temperature stability of high-Co magnets.Three original sintered Nd28.5Dy3-CoxFebalM0.6Bi(x=0,6 wt％,12 wt％;M=Cu,Al,Zr)magnets with different Co contents were diffused with Tb by grain boundary diffusion(GBD).After GBD,high-Co magnets exhibit more continuously distributed thin-layer GBs,and their thermal stability is significantly improved.In high-Co magnets(x=6 wt％),the absolute value of the temperature coefficient of coercivity decreases from 0.603％/K to 0.508％/K in the temperature range of 293-413 K,that of remanence decreases from 0.099％/K to 0.091％/K,and the coercivity increases from 18.44 to 25.04 kOe.Transmission electron microscopy(TEM)characterization reveals that there are both the 1∶2 phase and the amorphous phase in the high-Co magnet before and after GBD.EDS elemental analysis shows that Tb element is more likely to prefer-entially replace the rare earth elements in the 2∶14∶1 main phase than in the 1∶2 phase and the amor-phous phase.The concentration of Tb at the edge of the main phase is much higher than that in the 1∶2 phase and amorphous phase,which is beneficial to the improvement of the microstructure.The pref-erential replacement of Tb elements at the edge of the 2∶14∶1 phase and thin-layer GBs with a more continuous distribution are synergistically responsible for improving the thermal stability of high-Co magnets.The study indicates that GBD is an effective method to improve the microstructure and ther-mal stability of high-Co magnets.

Nd-Fe-B magnetsCoercivityGrain boundary diffusionThermal stabilityMicrostructureRare earths

Jiyuan Xu、Ruiyang Meng、Jing Liu、Jiateng Zhang、Rui Han、Yikun Fang、Shengzhi Dong、Wei Li

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Division of Functional Materials Research,Central Iron and Steel Research Institute,Beijing,100081,China

National Key R&D Program of ChinaNational Key R&D Program of ChinaNational Key R&D Program of ChinaNational Key R&D Program of China

2021YFB35029022021YFB35031002022YFB35033002022YFB3505200

2024

10.1016/j.jre.2023.10.023

稀土学报(英文版)
中国稀土学会

稀土学报(英文版)

CSTPCDEI
影响因子：1.3
ISSN：1002-0721
年,卷(期)：2024.42(8)
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