Preparation of Anisotropic NdFeB Powders by Crushing Sintered Magnet at High Temperatures (Ⅰ)

In order to manufacture anisotropic magnet powders from sintered NdFeB magnet, the fracture behavior of sintered NdFeB magnet in the mechanical crush process at high temperatures was studied. The experimental results show that the sintered NdFeB magnet can be crushed to fine powders much more easily than that at room temperature as the crushing temperature is raised to above 600℃, which results from eutectic formation of the minor liquid phase at the grain boundary area. The morphology of the crushed powders exhibits that the fracture at temperatures higher than the eutectic temperature tends to be intergranular instead of transgranular which occurs at lower temperatures. Through X-ray diffraction analysis the magnetic powders obtained by a crush process at higher temperatures shows much higher diffraction peaks of the Nd-rich phase.