Development of Dy-Free Nd-Fe-B Anisotropic Bonded Magnet and Application to the Small Motors

The authors have successfully developed a low-cost anisotropic Nd-Fe-B magnet powder with a high coercivity value of 1591 kAm−1 without any dysprosium additives by diffusion processing of Nd-Cu-Al element into anisotropic magnet powder produced by the d-HDDR (dynamic-hydrogenation, disproportionation, desorption and recombination) method. This enhancement mechanism is to isolate the magnetic coupling between the grains of Nd2Fe14B phase by a Nd rich grain boundary phase with Cu. By surface coating this anisotropic magnet powder, the long-term aging loss behavior under air at 150℃ is less than 5% after 1000 h. By using this new anisotropic bonded magnet (New-MAGFINE), small automotive motors with excellent thermal stability and low cost characteristics have become possible.