Enhanced alignment and magnetic properties of die-upset nano-crystal Nd2Fe14B magnets with Nb addition

It is difficult to obtain the crystallographic alignment for stoichiometric Nd2Fe14B alloys by applying the melt-spun and subsequent hot-pressing and hot-deformation techniques. However, the enhanced alignment and magnetic properties of die-upset nano-crystal Nd2Fe14B magnets have been obtained by Nb addition in the present paper. The magnetic properties studies show that Nb addition leads to the remarkable increase of remanence Br and intrinsic coercivity Hci, which is due to the improvement of c-axis texture and refinement of microstructure. Microstructure studies using transmission electron microscopy (TEM) and X-ray diffraction (XRD) reveal that Nb atoms are enriched at grain boundary and the NbFeB phase is observed with increasing Nb content. Since some Fe atoms in the Nd2Fe14B phase participate in the formation of NbFeB phase, the excessive Nd atoms may be enriched at grain boundary, which may improve the physical property of grain boundary and provide a mass transport pass for preferential growth of oriented Nd2Fe14B grains, thus leading to the enhanced alignment and magnetic properties.