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 1st annealing at 880℃for 2 h and then the 2nd annealing at 440℃for 3 h.It is exceptional to find out that both the remanence and coercivity are improved after 2nd 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 2nd annealed magnet,with a significant increment of 70.37％in coercivity.The extraordinary magnetic properties of Br=14.44 kGs,Hcj=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 distribu-tion patterns are altered after the 2nd 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.

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

Jiangxi Key Laboratory for Rare Earth Magnetic Materials and Devices&College of Rare Earths,Jiangxi University of Science and Technology,Ganzhou 341000,China;Fujian Key Laboratory for Rare Earth Functional Materials,Longyan 366300,China;School of Materials Science and Engineering,Taiyuan University of Science and Technology,Taiyuan 030024,China

材料科学技术（英文版）

[1]Qingfang Huang;Qingzheng Jiang;Jifan Hu;Sajjad Ur Rehman;Gang Fu;Qichen Quan;Jixiang Huang;Deqin Xu;Dakun Chen;Zhenchen Zhong-.Extraordinary simultaneous enhancement of the coercivity and remanence of dual alloy HRE-free Nd-Fe-B sintered magnets by post-sinter annealing)[J].材料科学技术（英文版）,2022(11):236-242

kGs

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