Influence of the Grain Size on the Dysprosium Diffusion in NdFeB Magnets

The dysprosium-diffused Nd2Fe14B magnets are a feasible way to increase coercivity and saving dysprosium at the same time. In the practice, a dysprosium source layer is placed over a NdFeB magnet substrate, and Dy diffusion takes place from the surface to the center of the substrate. This practical situation is modeled in the present study. The main microstructural variables are the grain size of the magnets and the volume fraction of the intergranular phase (Nd-rich), the modeling temperature of 900°C. It is found that this process may have increased kinetics if the grain is reduced or if the volume fraction of the intergranular phase is increased.