Toughness of Sintered NdFeB Magnets

The failure mechanism of sintered NdFeB magnets was studied from the view of fracture model and fracture mechanism, and the effect of alloying on strength and toughness of the magnets was researched too. The results showed that intercrystalline fracture was the main fracture model and cracks elongated along the interface between 2–14–1 phase and Nd-rich phase. Generally, the methods for improving toughness include enhancing bond strength of the interface between the two phases mentioned just, refining grains of 2–14–1 phase and increasing the amount of particles of Nd-rich phase localized at grain boundary. The fracture model of the Nd15.5Fe76.5Al1Ti0.5B6.5 magnets was transcrystalline cleavage fracture, whose value of fracture toughness increased about 30% compared to that of the Nd15.5Fe78B6.5 magnets. Otherwise, the value of fracture toughness of the magnets with a proper amount of addition of Ag increased about 70% compared to that of the Nd15.5Fe78B6.5 magnets. Moreover, the two sorts of modified magnet mentioned just could be drilled successfully. In addition, development of the research about increasing the strength and toughness of sintered NdFeB magnets is reviewed in this article.