The role of cobalt addition in magnetic and mechanical properties of high intrinsic coercivity Nd-Fe-B magnets

• Published in: Journal of alloys and compounds 2018-09, Vol.763, p.273-277
• Main Authors: Hu, Zhihua, Ma, Dongwei, Qu, Haijin, Zhang, Hongxia, Luo, Cheng, Wang, Huijie
• Format: Article
• Language: English
• Subjects: Anisotropy; Blending effects; Cobalt; Cobalt powders; Coercivity; Ferromagnetic phases; Ferromagnetism; Ferrous alloys; Fracture toughness; Grain boundaries; Iron; Magnetic materials; Magnetic properties; Magnetism; Magnets; Mechanical properties; Micron cobalt powder; Nd-Fe-B magnets; Neodymium; Rare earth elements
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2018.05.302

The role of cobalt addition in magnetic and mechanical properties of high intrinsic coercivity Nd-Fe-B magnets by adding cobalt element and blending micron cobalt powder was investigated. The results showed that the excellent magnetic properties of high intrinsic coercivity Nd-Fe-B magnets were obtained at the Co content of 1.5 wt%, and then the intrinsic coercivity and fracture toughness decline after blending 3 wt% micron Co powder. Blending Co powder increased the Co content of main phase grain and Nd-rich phase, and the phenomenon that the Co powder additive is in the presence of pure Co particles was not been found in the sample. Simultaneously, blending Co powder reduced the heavy rare earth content of main phase grain, and new phases containing heavy rare earth and Co were formed, such as soft ferromagnetic phase R(FeCo)3, the low-anisotropy phase R(FeCo)5 and rich-B phase R1.1(FeCo)4B4. These phenomena lead to a decrease in the intrinsic coercivity of high intrinsic coercivity Nd-Fe-B magnets. Further investigation on the grain and grain boundary indicated that the effect mechanism of blending Co powder on magnetic properties is not the same as that of the traditional alloying route. •The Co powder addition reduces the intrinsic coercivity and fracture toughness of magnets.•The addition of Co powder improves the temperature coefficient of remanence.•The Co powder addition is not in the form of pure Co particles, but diffuses into the grain.