Crystallographic alignment of Fe2B and Nd2Fe14B for texture memory in hydrogenation–disproportionation–desorption–recombination-processed Nd–Fe–B powders

Abstract

Texture development in hydrogenation–disproportionation–desorption–recombination (HDDR)-processed NdFeB magnets is discussed with a focus on the crystallographic alignment of the Nd2Fe14B and Fe2B phases. By careful control of the dynamic HDDR-processing parameters, shape changes in the HDDR-treated samples were minimized by suitable modifications to the sample dimensions to trace the orientation relation between the c-axes of the Nd2Fe14B and Fe2B phases. The magnetic anisotropy was significantly dependent on the hydrogen pressure during the HD process and highly aligned Fe2B phases, with the same c-axis orientation as the initial Nd2Fe14B phase, were formed under the dynamic HDDR treatment at a hydrogen pressure of 30 kPa under controlled HD conditions. During the DR reaction following the HD process, the orientation of the initial Nd2Fe14B was recovered by a highly aligned Fe2B phase. It was demonstrated that the Fe2B phase could mediate texture during the HDDR processing owing to the atomic configuration and crystallographic relation between the Nd2Fe14B and Fe2B phases.