Suppressing the CeFe2 phase formation and improving the coercivity and thermal stability of Ce-Fe-B alloys by Si substitution. (April 2019)

• Record Type: Journal Article
• Authors: Zhang, J.S.; Zhao, L.Z.; Liao, X.F.; Zeng, H.X.; Peng, D.R.; Yu, H.Y.; Zhong, X.C.; Liu, Z.W.
• Is Part Of: Intermetallics. Volume 107(2019:Apr.)
• Page Start: 75
• Page End: 80
• Publication Date: 2019-04
• Subjects: Ce-Fe-B magnets -- Magnetic properties -- Curie temperature -- Thermal stability -- Coercivity mechanism; Intermetallic compounds -- Metallography -- Periodicals; Metallic glasses -- Periodicals; Composés intermétalliques -- Métallographie -- Périodiques; 669.94
• DOI: 10.1016/j.intermet.2019.01.013
• Languages: English
• ISSNs: 0966-9795

Abstract

Abstract: Low anisotropy field and low Curie temperature of Ce2 Fe14 B phase seriously restrict the application of Ce-Fe-B alloys. Most of the previous work suggest that REFe2 phase inevitably forms in the compositions with high Ce content. In this work, Si substitution for Fe is found to not only suppress the formation of CeFe2 phase, but also significantly improve the coercivity H c and thermal stability of Ce17 Fe78-x Six B6 (x = 0–3.0) alloys. All Si-doped alloys exhibit higher H c and better thermal stability than Ce17 Fe78 B6 alloy. With increasing Si doping, a relatively high H c = 525 kA/m is obtained in the Ce17 Fe77.75 Si0.25 B6 alloy. An abnormal increase of H c as well as almost unchanged J r and ( BH )max is observed in Ce17 Fe78-x Six B6 (x > 1.5) alloys. The refined XRD results indicate that the volume fraction of CeFe2 phase can be dramatically reduced via a moderate content of Si doping. Hard magnetic grains are isolated by forming a structure with thin and continuous intermediate layer, consequently preventing the domain wall propagation. The Curie temperature of the main phase monotonically increases from 424 K for x = 0–445 K for x = 3.0, resulting in improved thermal stability. The highest H c of 530 kA/m, the lowest temperature coefficients (| β | = 0.551%/°C and | α | = 0.368%/°C), and an acceptable J r = 0.44 T are obtained in Ce17 Fe78-x Six B6 (x = 3.0) alloy. The nucleation and pinning are both responsible for the coercivity mechanism of Ce17 Fe75 Si3 B6 alloy, which should be the reason for its high coercivity. Highlights: The formation of undesired CeFe2 phase is suppressed by Si doping. Si doping increases Curie temperature and improves thermal stability. A structure with thin and continuous grain boundary phase is formed by Si doping. Increased Hc and almost unchanged J r and ( BH )max can be obtained in Si doped alloys. A domain wall pinning effect is observed in Ce17 Fe75 Si3 B6 alloy.