Grain Boundary Diffusion Technology

Grain boundary diffusion technology (GBD) is an interface composition technology which makes heavy rare earth elements enter the grain boundary to enhance partial anisotropy field and thus improve the intrinsic coercivity and thermal stability of the material while remanence is basically unchanged. The process starts by introducing HREE layer to the magnet’s surface, then processing vacuum heat treatment above the melting point of Nd-rich phase. Thereby, HREE element diffuse into the magnet along the grain boundaries and form (Nd, Dy, Tb) 2 Fe 14 B core-shell structure around main phase grain.Unlike conventional metallurgy process, grain boundary diffusion elements do not require to enter the main phase and minimizes the heavy rare earth usage which is favorable for improving cost performance. Even GBD technology can create new grade with higher remanence and intrinsic coercivity that were previously unattainable with conventional process, but it should be noted that the feasibility of the GBD technology tends to vary according to the detailed shape and grade.