Study on the Magnetic and Mechanical Properties of Dy-diffused Nd-Dy-Fe-B Magnets

Understanding the synergistic mechanism of the Dy element in grain-boundary-diffused Nd-Fe-B magnets is important for enhancing the performance of these magnets. In this paper, the magnetic and mechanical properties of Dy-diffused Nd-Dy-Fe-B magnets were investigated. Results showed that Dy in the matrix increased the H_cj of the matrix, but reduced the ΔH_cj of diffused magnets. The fracture toughness of the matrices decreased with increasing Dy content. Still, it was higher than that of corresponding diffused magnets, indicating that Dy grain boundary diffusion reduced the fracture toughness of Nd-Dy-Fe-B magnets. The increase in Dy content in matrices led to the formation of core-shell structure (Dy-rich core and Dy-lean shell) grains, resulting in a decrease in the utilization efficiency of the Dy element during the grain boundary diffusion process (GBDP). These results demonstrated the synergistic effect of Dy, providing a theoretical basis for reducing its content in diffused magnets.