Phase composition tailoring and coercivity mechanism of high-performance high-abundance rare-earth sintered magnets

• Published in: Acta materialia 2025-01, Vol.284, p.120625, Article 120625
• Main Authors: Zhang, Lele, Li, Yuqing, Bian, Mengying, Zhang, Hongguo, Chen, Hao, Qin, Yuan, Li, Qian, Liu, Weiqiang, Zhu, Minggang, Yue, Ming
• Format: Article
• Language: English
• Subjects: Coercivity mechanism; Dual-main-phase; Heterogeneity; Phase composition tailoring; Sintered magnets
• ISSN: 1359-6454
• DOI: 10.1016/j.actamat.2024.120625

The widespread adoption of Nd-Fe-B magnets with abundant and cheap Ce substitution for Nd is significantly constrained by the inherently inferior magnetic properties exhibited by Ce-Fe-B. In this study, high-performance Nd-Ce-Fe-B sintered magnets with Nd-Fe-B + Ce-Fe-B (N-C-type) and Nd-Fe-B + (Nd, Ce)-Fe-B (N-NC-type) compositions are successfully developed through the design of dual-alloy components, which facilitate precise control over the distribution of rare-earth (RE) elements in the dual-main-phase grains. The N-C-type exhibits higher remanence (Br) and magnetic energy product [(BH)max], whereas the N-NC-type demonstrates higher coercivity (Hcj). The magnetic properties of the as-sintered magnet with 20 wt.% of Ce over the total RE content are optimized via Br of 14.25 kG, Hcj of 8.6 kOe, and (BH)max of 48.6 MGOe. After annealing, Hcj increases to greater than 10 kOe and (BH)max remains at 47 MGOe. Through the implementation of reasonable composition design and the optimization the preparation processes in these grains, the RE elements exhibit a clear stepwise heterogeneity of the chemical composition in their core-shell structure, whereas the shell structures of these grains display a homogeneity of chemical composition. The results provide a reference for the composition design and development of high-performance high-abundance RE sintered magnets for enhancing the utilization of high-abundance RE elements in permanent magnetic materials and contributing to a more balanced exploitation of RE resources. [Display omitted] Fig. 1(a) Schematic diagram showing the distribution regulation of rare-earth elements in the main-phase grains, the remanence trend Mr (exp.), saturation magnetization Ms (exp.), Ms (theo.), and Ms (calc.) of (b) NNC-Type and (c) NC-Type dual-main phase sintered magnets, and (d) the trend of magnetic properties of the C20–C60 dual-main phase sintered magnets [12,17,30,34,37–44].