Enhancement mechanism of maximum energy product in hot-deformed Nd-Fe-B magnets by addition of ferromagnetic substances*

It has been proved that the maximum magnetic energy product (BH)max of hot-deformed Nd-Fe-B magnets can be effectively improved by adding substances with either high melting point or high saturation magnetization. In this work, we selected a ferromagnetic nano Fe55Ni28Co17 alloy powders with both high melting point and high saturation magnetization as the dopant to improve the (BH)max. By the addition of 1 wt% FeNiCo, the remanence increases by over 5% (from 1.36 to 1.44 T), resulting in a significant enhancement of (BH)max from 355 to 396 kJ/m3 (from 44.6 to 49.7 MGOe). Microstructure observations reveal that the texture of grain alignment is improved, the concentrations of ferromagnetic elements (Fe, Ni, and Co) in the main phase and intergranular phase are increased so that the magnetization behavior of hot-deformed magnet changes (more easily shows reversible magnetization behaviors), which are the reasons why the high maximum energy product of hot-deformed magnet, is obtained.