A Comparative Study of Diffusion Sources for Improved Magnetic Properties of NdFeB Magnets

Abstract

This study focuses on sintered NdFeB magnets and systematically examines the diffusion behavior and its impact on magnetic properties using three types of diffusion sources: DyF₃ powder, a mixed powder of DyF₃ and Pr₇₀Co₁₅Al₁₅ alloy, and Pr₆₀Dy₁₀Co₁₅Al₁₅ alloy powder. The findings demonstrate that the Pr₆₀Dy₁₀Co₁₅Al₁₅ alloy diffusion source produces the most favorable outcomes, with an enhancement in coercivity by 6.9 kOe. The composite diffusion source demonstrates a 5.83-kOe increase, while the fluoride diffusion source exhibits the least improvement, with a 4.21-kOe increase. The diffusion of DyF₃ is constrained by its high decomposition temperature and interference from F elements, which limit the depth of diffusion of Dy. The composite diffusion source, through the liquid-phase diffusion of Pr₇₀Co₁₅Al₁₅ alloy, has the effect of improving the wettability of grain boundaries and the channels of diffusion, which significantly increases the depth of diffusion of Dy elements. In the Pr₆₀Dy₁₀Co₁₅Al₁₅ alloy diffusion source, the synergistic diffusion of Dy, Pr, and Al elements enhances diffusion efficiency. Moreover, extending the diffusion time allows for further optimization of the grain boundary structure, thus facilitating deeper diffusion of Dy elements. This study thus demonstrates the superiority of the Pr₆₀Dy₁₀Co₁₅Al₁₅ alloy diffusion source, providing a crucial foundation for the efficient use of rare earth resources and the development of high-performance magnets.