Understanding the element segregation and phase separation in the Ce-substituted Nd-(Fe,Co)-B based alloys

L Z Zhao; J S Zhang; G Ahmed; X F Liao; Z W Liu; J M Greneche

doi:10.1038/s41598-018-25230-0

Understanding the element segregation and phase separation in the Ce-substituted Nd-(Fe,Co)-B based alloys

Sci Rep. 2018 May 1;8(1):6826. doi: 10.1038/s41598-018-25230-0.

Authors

L Z Zhao^{1

2}, J S Zhang³, G Ahmed³, X F Liao³, Z W Liu⁴, J M Greneche⁵

Affiliations

¹ School of Materials Science and Engineering, South China University of Technology, Guangzhou, 510640, China. lzzhao@hdu.edu.cn.
² Innovative Center for Advanced Materials (ICAM), Hangzhou Dianzi University, Hangzhou, 310012, China. lzzhao@hdu.edu.cn.
³ School of Materials Science and Engineering, South China University of Technology, Guangzhou, 510640, China.
⁴ School of Materials Science and Engineering, South China University of Technology, Guangzhou, 510640, China. zwliu@scut.edu.cn.
⁵ Institut des Molécules et Matériaux du Mans CNRS UMR-6283, Le Mans Université, Avenue Messiaen, Le Mans, F-72085, France.

Abstract

Ce substituted Nd₂Fe₁₄B (2:14:1)-type permanent magnets have shown increasing potential in the applications due to their high properties/cost ratio. However, the element segregation and phase separation in the Ce substituted magnets have not been fully understood yet. In this work, (Nd_1-xCe_x)₂₅Fe₄₀Co₂₀Al₄B₁₁ alloys with high coercivities were prepared by copper mold casting. Based on detailed microstructure and composition analysis, the segregation of rare earth (RE) elements was observed in the as-cast alloys. Nd element prefers to enter into the 2:14:1 phase and the Ce element enter into the 1:2 phase. The existence of the 1:2 phase can promote the element segregation. The alloy shows an abnormal increase of coercivity from 641 kA/m for x = 0.2 to 863 kA/m for x = 0.3. This increase could be attributed to the phase separation of the 2:14:1 phase, which has been confirmed by the microstructural characterization. The present data provides useful information for exploring Ce-containing Nd-Fe-B magnets.