Dy-reduced High-Performance Nd-Fe-B Magnet by Two-Step Diffusion Process
Currently, (Nd,Dy)-Fe-B sintered magnets are employed in the traction motors of hybrid and electric vehicles. Dysprosium (Dy) is required to maintain the coercivity of Nd-Fe-B sintered magnets at their operating temperature. However, the limited availability of Dy as a natural resource has prompted researchers to pursue the development of high-coercivity Nd-Fe-B permanent magnets with reduced or no Dy content. A high coercivity of 2.5 T can be achieved in a 5.6-mm-thick anisotropic Nd-Fe-B magnet by applying a two-step diffusion process using Nd50Dy30Cu20 and Nd80Cu20 eutectic alloys to a Dy-free hot-deformed Nd-Fe-B magnet. The overall Dy concentration in the magnet was measured to be only 0.45 wt.%, which is about 10% of the Dy content used in conventional (Nd,Dy)-Fe-B sintered magnets with comparable coercivity. Owing to the reduced Dy concentration, a relatively high remanence of 1.32 T is preserved even after the two-step diffusion process. The property-microstructure relationship was elucidated through multi-scale analysis using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atom probe tomography (APT).
- M. Korent, Xin Tang, H. Sepehri-Amin, K. Hioki, K.Ž. Soderžnik, S. Kobe, T. Ohkubo, and K. Hono, "Significant coercivity enhancement of hot-deformed bulk magnets by two-step diffusion process using a minimal amount of Dy", Scr. Mater. 205, 114207 (2021)
Regarding This Research:
Hossein SEPEHRI-AMIN, Group Leader of Green Magnetic Materials Group at NIMS
E-mail: H.SEPEHRIAMIN[at]nims.go.jp