晶界添加Dy_79.73Fe_20.27对烧结钕铁硼微观结构和磁性能的影响

The advantages of grain boundary diffusion in improving coercivity of sintered NdFeB magnets are vast. However, due to the need for special equipment and processes, and the size limitations of diffused magnets, the practicality of grain boundary diffusion is limited. Some literatures reported adding Dy-containing alloys to the grain boundary directly, the magnets are no longer limited by size, and similar diffusive results can be obtained, but the alloys need to be specially fabricated. The process of preparing the Dy alloy and special equipment can be omitted also, we choose easier to obtain the Dy₈₀Fe₂₀ (mass fraction) alloy, which is the raw material for sintered Nd-Fe-B magnet production, the actual alloy used in the experiment is Dy_79.73Fe_20.27. The first annealing time is extended from 3 h to 7 h, simultaneously. In this method of grain boundary supplementation there are many advantages: the grain boundary is clearer, more complete and continuous, the decoupling effect is better, and H_cj is improved. Moreover, Dy introduced into the magnet grain surface forms a thin (Pr,Nd,Dy)₂Fe₁₄B hard magnetic shell to effectively improve H_cj. The improvement of H_cj obtained by the research is better than that reported in some literatures. This process is no longer limited by the size of the magnets and can produce larger magnets, and it does not need the special equipment. The sintered Nd-Fe-B magnets with magnetic properties of B_r=13.89 kGs H_cj=21.32 kOe, and (BH)_max=47.43 MGOe was obtained. This process also has guiding significance for actual batch production.