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

Abstract

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 H_cj is obviously improved, and its maximum increment is ∼12.3 % at 4 wt% Gd₆₀Y₁₀Cu₁₅Al₁₅ alloy. Especially, the increase in H_cj 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 H_cj (β) and B_r (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.