Comparison of local and global texture in HDDR processed Nd–Fe–B magnets

Abstract

The local texture in polycrystalline Nd–Fe–B powder particles processed by hydrogenation disproportionation desorption and recombination (HDDR) has, for the first time, been observed directly by electron backscatter diffraction (EBSD). The local texture quality was found to vary strongly with the hydrogen pressure applied during HDDR processing. At 0.3 bar, a strong biaxial local texture occurs in the individual powder particles. Increasing the hydrogen pressure during HDDR results initially in a lower texture quality and finally leads to near-isotropic particles. Clusters of similarly oriented grains within near-isotropic particles were observed rather than a completely random spatial distribution of orientations. The local texture within the powder particles was shown to be critical in determining the magnetic properties of compacts produced by aligning the powder in an external magnetic field. A compact produced from the powder with the strongest local texture (processed at 0.3 bar) showed highly anisotropic magnetic properties with remanence (related to the density of Nd 2Fe 14B) parallel and perpendicular to the applied field direction of 1.24 T and 0.55 T, respectively.