Effect of post-sinter annealing on structure and coercivity of (Zr, Ti)-doped Nd-Ce-Fe-B magnets

• Published in: Journal of alloys and compounds 2024-06, Vol.990, p.174479, Article 174479
• Main Authors: Wang, Zhiwei, Ni, Junjie, Song, Bo, Wang, Xuegeng, Liu, Xiaolian, Xu, Kai, Zhou, Shutai, Hu, Chengchao, Xu, Yue, Luo, Laima
• Format: Article
• Language: English
• Subjects: Annealing; Coercivity; Microstructure; Nd-Fe-B magnet
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2024.174479

Post-sinter annealing effects on the structure and coercivity have been investigated for the (Zr, Ti)-doped Nd-Ce-Fe-B sintered magnets. In them, an in-situ formed Zr-rich Zr-Ti phase with the strip shape is found to be beneficial for the coercivity Hcj, because its distribution along grain boundaries (GBs) after annealing at 700℃ can block the magnetic domain within matrix phases passing through the adjacent RE2Fe14B grains. It, coupled with the optimized distribution of RE-rich phase, accounts for the 21.1 % increase of Hcj before and after annealing at 700 ℃. This temperature much higher than the melting-point (465 ℃) of RE-rich phase is the optimum annealing temperature, at which the RE-rich liquid phase is good for the distribution of Zr-Ti phase along GBs rather than at triple junction regions, optimizing GB microstructure. Such new findings deepen the understanding on microstructure evolutions of the GB modified Nd-Fe-B magnet during annealing and further provide a theoretical basis for the Hcj improvement. •In-situ formed Zr-Ti phase with strip shape can increase coercivity of (Zr,Ti)-doped Nd-Ce-Fe-B magnets.•Coercivity can be increased by 21.1 % before and after annealing at 700 ℃.•Magnet structure evolution during annealing and its effect mechanism on coercivity were clarified.