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Magnetic performance of hybrid Nd-Fe-B/Ce-Fe-B hot-deformed magnets
Ye Ryeong Jang,Wonjin Kim,Seung Yong Lee,Hyun-Sook Lee,Wooyoung Lee 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.2
With a rapid increase in demand for Nd–Fe–B magnets, Ce-based magnets have received a lot of attention in recent years for their potential use of permanent magnets. This is because Ce has much more natural reserves and a relatively lower selling price compared to Nd and Pr. However, Ce substitution for Nd in the 2:14:1 phase weaken the magnetic properties due to the low intrinsic magnetic properties of Ce₂Fe14B (saturation magnetization 11.7 kG, magnetocrystalline anisotropy field 30 kOe). Therefore, the fabrication of high performance Nd-Fe-B magnet, in which Nd is partially or completely replaced by Ce, is still challenging issues. In this study, we investigated the magnetic performance of hybrid Nd-Fe-B/Ce-Fe-B hot deformed magnet. We designed a dual main phase (DMP) hot deformed magnets by mixing Ce-free and Ce-containing Nd-Fe-B powders. The melt-spun ribbons of Ce-Fe-B and Nd-Fe-B were mixed in various ratios and prepared into powders. The magnetic performance of the magnets was investigated by changing the contents of Ce-Fe-B and Nd-Fe-B in the range of 50–100 wt% and 50–0 wt%, respectively. For best magnetic performance, the hot deform temperature was adjusted in the range of 700–850 ℃. We analyzed the microstructure of the DMP magnets compared to SMP (single main phase) magnets. Finally, we evaluated the possibility of the hybrid Nd-Fe-B/Ce-Fe-B hot deformed magnet as a potential candidate for low-cost medium performance ((BH)max = 20 MGOe) permanent magnet.
Grain Boundary Diffusion of La Based Low-melting Alloy to Nd-Fe-B Sintered Magnets
Ye Ryeong Jang,Hyungju Lee,Jaeryung Lee,Hyun-Sook Lee,Wooyoung Lee 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.1
The high-performance Nd-Fe-B magnets have been widely used in many different applications, such as motors, generators, actuators, hard disk drives, and communication devices, since their discovery in 1894. In order to improve the performance of Nd-Fe-B magnets, grain boundary diffusion process is carried out by using heavy rare-earth element (HRE) such as Dy or Tb. Many efforts have been made to prepare high-performance Dy/Tb diffused Nd-Fe-B sintered magnets. However, these heavy rare-earth elements (Dy, Tb) have a problem that prices and supply are unstable. In this study, we have investigated the magnetic properties of Light rare-earth element (LRE) diffused Nd–Fe–B magnets. The alloys containing less expensive rare-earth element and low-melting metals work effectively as diffusion sources. Metals or compounds with low melting points can modify boundary structure by improving the wettability between intergranular phases and matrix phases. La based alloys effectively diffused along grain boundary phases and formed non-ferromagnetic phases, improving exchange decoupling and enhancing the coercivity. In order to analyze the microstructures, we use scanning electron microscopy. It is expected to provide solutions for cost reduction of GBDP and NdFeB magnets production by saving rare-earth resource. (See text for figure)