Nd2Fe17 nanograins effect on the coercivity of HDDR NdFeB magnets with low boron content

Relationships between the coercivity of hydrogenation disproportionation desorption recombination (HDDR) NdFeCoB bonded magnets and boron content were investigated. NdFe phase with planar magnetic anisotropy is present in the microstructure when = 4at%–5.88at%, which does not reduce the coercivity of the bonded magnets. High-resolution transmission electron microscopy (TEM) images show that NdFe phase exists in the form of nanocrystals in the Nd2Fe14B matrix. There is an exchange-coupling interaction between the two phases so that the coercivity of HDDR NdFeCoB bonded magnets is hardly reduced with a decrease in boron content.