Synergistic enhancement of coercivity and thermal stability of nanocrystalline multi-main-phase Nd-Ce-Fe-B magnet via Gd60Y10Cu15Al15 addition

Nanocrystalline multi-main-phase (MMP) Nd-Ce-Fe-B magnet can effectively suppress the magnetic dilution effect of Ce. However, its low coercivity and poor thermal stability have not been adequately overcome. In this work, a novel low-melting-point Gd60Y10Cu15Al15 alloy was introduced into MMP Nd-Ce-Fe-B magnet through intergranular addition for simultaneously enhancing its coercivity and thermal stability. The results show that the intrinsic coercivity Hcj is obviously improved, and its maximum increment is ∼12.3 % at 4 wt% Gd60Y10Cu15Al15 alloy. Especially, the increase in Hcj is more significant, and an abnormally increase in the maximum energy product (BH)max occurs at high temperature of 150 °C. Meanwhile, the reversible temperature coefficients of Hcj (β) and Br (α) are improved simultaneously. These findings imply the enhanced thermal stability for the MMP magnet with Gd60Y10Cu15Al15 addition. The microstructural characterizations, compositional analyses and micromagnetic simulations reveal that the competitive effects of the formed non-ferromagnetic grain boundary (GB) phase and Y or Gd diffusion into the main phase lead mainly to a synergistic improvement in the coercivity and thermal stability of the magnet. This work is expected to provide a promising cost-effective approach for developing the high-performance thermally-stable Nd-Ce-Fe-B magnet and explore more possibilities for effective utilization of Y or Gd rare-earth resources. •The Research Highlights in this paper are as follows:•A novel low-melting-point Y-Gd based alloy was developed and used to modify the nanocrystalline MMP Nd-Ce-Fe-B magnet.•Hcj and thermal stability of nanocrystalline MMP magnet are synergistically enhanced.•Microstructure evolutions and composition distributions are revealed.•The enhanced mechanisms for Hcj and thermal stability are systematically analyzed.