Fracture behavior of sintered NdFeB magnets during cooling from sintering temperature

In order to explore fracture behavior of sintered NdFeB magnets during cooling from sintering temperature, in this work, we analyzed microstructure and grains distribution of the fractured samples. Because of grains irregular growth, the Nd-rich phase reunited at grain-junction region, causing internal stress concentration on grain boundary. The fracture surface showed an intergranular fracture. Cracks advanced incrementally with each stress formed at the magnet center. The propagation speed of cracks was different at different regions. Magnetic flux density decreased in the fractured section. Based on the experimental results, a fracture model has been constructed for magnets. The model can better clarify the mechanism of intergranular fracture along the grain boundaries.