Highly Efficient Diffusion TbF 3 to Enhance the Coercivity of Sintered Nd-Fe-B Magnet by Cu Addition

In this paper, Cu element was added to the grain boundary of sintered Nd-Fe-B magnet to form a low melting point alloy phase in the grain boundary to promote the diffusion depth of Tb element. The intrinsic coercivity of the magnet with 0.2 % Cu addition increased significantly from 16.07 kOe for standard alloy without Cu to 24.38 kOe after the diffusion of TbF3 . The squareness of the demagnetization curves is maintained at 94 %, ensuring a good diffusion efficiency and uniformity. EPMA analysis showed that the distribution depth of (Nd, Tb) 2 Fe 14 B core-shell layer of the magnet was increased from 50 μm to 145 μm after the diffusion. The addition of Cu increased the ratio and average area of the grain boundary phases effectively, and formed a good diffusion channel. A larger amount of (Nd, Tb) 2 Fe 14 B shell layers formed in the magnet as a result of TbF 3 diffusion in Cu added magnets and which increased the intrinsic coercivity due to enhanced magnetocryalline anisotropy and favorable microstructure.In this paper, Cu element was added to the grain boundary of sintered Nd-Fe-B magnet to form a low melting point alloy phase in the grain boundary to promote the diffusion depth of Tb element. The intrinsic coercivity of the magnet with 0.2 % Cu addition increased significantly from 16.07 kOe for standard alloy without Cu to 24.38 kOe after the diffusion of TbF3 . The squareness of the demagnetization curves is maintained at 94%, ensuring a good diffusion efficiency and uniformity. EPMA analysis showed that the distribution depth of (Nd, Tb) 2 Fe 14 B core-shell layer of the magnet was increased from 50 μm to 145 μm after the diffusion. The addition of Cu increased the ratio and average area of the grain boundary phases effectively, and formed a good diffusion channel. A larger amount of (Nd,Tb)2Fe14B shell layers formed in the magnet as a result of TbF3 diffusion in Cu added magnets which increased the intrinsic coercivity due to enhanced magnetocryalline anisotropy and favorable microstructure.