Effect of grain boundary reconstruction and regenerated main phase shell on magnetic properties in high-abundance (NdLaCeY)-Fe-B magnets

The (NdLaCeY)-Fe-B magnets with 45–50 wt% high-abundance rare earth substitution were systematically investigated by co-mixing high boron content matrix phase and Pr–Fe alloy powders (0, 1, 3, 5, 7, and 9 wt%) during the preparation process. The coercivity of magnets increased successively with the addition of Pr70Fe30 (wt.%) and reached 9.32 kOe at the addition amount of 9 wt% from the initial 7.33 kOe without addition, while the remanence had a very small decrease of only 0.13 kGs. The analyses showed that the B-rich phase in the high-boron powders reacted with Pr70Fe30 to form the main phase shell, forming a core-shell structure with a Pr-rich shell and a Y-rich core. Meanwhile, the grain boundary was significantly widened with the introduction of Pr70Fe30. Then, just the improved anisotropy of the main phase grain surface, accompanied with the enhanced magnetic de-coupling effect between the main phase grains, resulted in a great coercivity increment. Notably, on the remanence, the beneficial effect of increased main-phase proportion by regenerated grain shell had a competitive relationship with the deteriorating effect of the magnetic dilution by the non-magnetic material introduction, thus under the combined effects, the remanence firstly increased and then decreased with the addition of Pr–Fe.