Search

The grain boundary diffusion process (GBDP) has become an important technique in improving the coercivity and thermal stability of Dy-free sintered Nd-Fe-B magnets. The influence of Dy70Al10Ga20 and (Pr75Dy25)70Al10Ga20 alloys by the GBDP on sintered Nd-Fe-B magnets are investigated in this paper. After diffusing Dy70Al10Ga20 and (Pr75Dy25)70Al10Ga20 alloys, the coercivity (Hcj) of the magnets increased from 13.58 kOe to 20.10 kOe and 18.11 kOe, respectively. Meanwhile, the remanence of the magnets decreased slightly. The thermal stability of the diffused magnets was improved by the GBDP. The microstructure shows continuous Rare-earth-rich (RE-rich) grain boundary phases and (Dy, Pr/Nd)2Fe14B core-shell structures which contribute to improving the coercivity. Moreover, the Dy concentration on the surface of the (Pr75Dy25)70Al10Ga20 diffused magnets decreased with the Pr substitution for the Dy element. The openness of the recoil loops for the (Pr75Dy25)70Al10Ga20 diffused magnets is smaller than that of the original magnets and Dy70Al10Ga20 diffused magnets. The results show that the (Pr75Dy25)70Al10Ga20 alloys can effectively optimize the microstructure and improve the magnetic properties and thermal stability of the sintered Nd-Fe-B magnets. [ABSTRACT FROM AUTHOR]

• The magnetic properties and microstructures of commercial Nd-La-Y-Fe-B permanent magnets grain boundary diffused with PrCuGa were systematically studied. • Both the H cj and (BH) max of the magnets are obviously improved from 13.6 kOe, 32.2 MGOe to 18.3 kOe, 33.2 MGOe, respectively. • Pr enters into the main phases, leading to the increased H A and M s of 2:14:1 phases. Ga and Cu elements in the grain boundary is advantageous to make the grain boundary phases clear and continuous, resulting in weakened exchange coupling interaction. Committed to acquiring cost-effective Nd-Fe-B based permanent magnets, commercial Nd-La-Y-Fe-B magnets had been grain boundary diffused with PrCuGa as the diffusion source. The optimized magnetic properties had been obtained when the magnet was annealed at 930 ℃. The H cj and (BH) max increased from 13.6 kOe, 32.2 MGOe to 18.3 kOe, 33.2 MGOe respectively. The results show that the concentration of Pr in the grain boundary phase increases after the diffusion of PrCuGa, and the characteristic peak of the matrix magnet shifts to a large angle from the XRD pattern. Both H cj and (BH) max are improved because Pr partially replaces La to from (Pr,Nd,La,Y) 2 Fe 14 B with higher intrinsic properties. In addition, Cu and Ga elements improve the continuity of the grain boundary phases and isolate the short-range exchange coupling between the main phase grains, contributing to the increased H cj. [ABSTRACT FROM AUTHOR]

In this work, the high performance NdFeB magnet were fabricated by double alloy method and grain boundary diffusion Tb 70 Cu 20 Ga 10 alloys. The maximum energy product (BH) max and coercivity H cj of the magnet are 45.33 MGOe and 35.46 kOe, respectively. The reversible temperature coefficients of coercivity of the diffusion magnets improve from − 0.456%/°C to − 0.412%/°C at the range of 22 °C −180 °C. The magnetostatic loss of NdFeB magnet was analyzed in high temperature applications by general finite element method (FEM). The RE-(Fe,CuGaO) grain boundary phases and double Tb-rich/lean shells improve the utilization rate of heavy rare earths and coercivity of magnets after diffusion. The magnetization reversal mechanism of double core-shell microstructures had been discussed. This work may shed light on developing coercivity above 30 kOe of NdFeB magnet with low heavy rare earth through modified microstructure. • High coercivity magnet achieve by diffusing Tb 70 Cu 20 Ga 10. • The magnetization reversal of double core-shell structures was discussed. [ABSTRACT FROM AUTHOR]

• This study provides a method using of Tb hydride in suspension to improve coercivity in sintered NdFeB magnets. • This work investigated Tb diffusion behavior from coating layer to the magnet. • Tb rich core-shell structure and continuous grain boundary in the magnet, which effective increase in coercivity. Grain boundary diffusion of Tb can improve the microstructural and magnetic properties of NdFeB magnets. In this paper, we investigated diffusion behavior and coercivity enhancement by dip-coating TbH 3 powders in sintered NdFeB magnets. The results show that the coercivity increased rapidly from 14.02 kOe to 23.72 kOe after diffusion. Tb atoms diffused to the surface of the magnet and then into the interior, forming a network Tb-rich shell around (PrNd) 2 Fe 14 B grains. The higher magnetocrystalline anisotropy (PrNd,Tb) 2 Fe 14 B phases determine the coercivity enhancement. The Tb diffusion model was build up from coating layer to the magnet. This work may shed light on developing sintered NdFeB magnets with coercivity enhancement by diffusion technology. [ABSTRACT FROM AUTHOR]