The effect of density distribution on alignment uniformity of Nd-Fe-B compact: Discrete element method (DEM) and experiments

The microstructure and performance of Nd-Fe-B magnets are significantly influenced by the density, alignment, and their distributions in green compacts. In this paper, the variations in magnetic alignment, density, and strength of green compacts during the magnetic pressing process were investigated by a discrete element method (DEM) and experiments. The results revealed an uneven density distribution in compacts, with higher density at the corners due to various friction effects during the pressing process. The simulated and experimental investigations verified that the uniform density distribution can diminish relative movement among adjacent particles and stress concentration in compacts, further improving the uniformity of alignment distribution. Additionally, the factors affecting the distribution uniformity of density and alignment in compacts were explored. It was demonstrated that the distribution uniformity of density and alignment can be enhanced by decreasing the friction coefficient among particles, increasing the filling density, and applying the rubber punch.