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

Abstract

Relationships between the coercivity of hydrogenation disproportionation desorption recombination (HDDR) Nd_12.5Fe_81.5−xCo₆B _x bonded magnets and boron content were investigated. Nd₂Fe₁₇ phase with planar magnetic anisotropy is present in the microstructure when x= 4at%–5.88at%, which does not reduce the coercivity of the bonded magnets. High-resolution transmission electron microscopy (TEM) images show that Nd₂Fe₁₇ 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 Nd_12.5Fe_81.5−xCo₆B _x bonded magnets is hardly reduced with a decrease in boron content.

Keywords

permanent magnets / magnetic properties / boron / microstructure / nanocrystals

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