Coercivity enhancement of NdFeB sintered magnets by low melting point Dy_32.5Fe₆₂Cu_5.5 alloy modification

To improve coercivity without sacrificing other magnetic performance of NdFeB sintered magnets, a low melting point Dy_32.5Fe ₆₂Cu_5.5 alloy was introduced as an intergranular additive. Magnetic properties and microstructure of the magnets with different Dy _32.5Fe₆₂Cu_5.5 contents were studied. At the optimum addition of 3 wt%, coercivity H_cj was enhanced from 12.7 to 15.2 kOe, the maximum magnetic energy product (BH)_max was simultaneously increased from 46.6 to 47.8 MG Oe, accompanied by a slight reduction in remanence B_r. Further investigation on microstructure and grain boundary composition indicated that the enhanced H_cj and (BH)_max could be attributed to the refined and uniform 2:14:1 phase grains, continuous grain boundaries and a (Nd,Dy)₂Fe₁₄B hardening shell surrounding the 2:14:1 phase grains.