Anisotropic local hardening in hot-deformed Nd-Fe-B permanent magnets

Misorientations across boundary planes in a sintered NdFeB permanent magnet

“…For N/R boundaries, Nd-Rich phases magnetically isolate the individual Nd 2 Fe 14 B crystals from each other and form shell structure around Nd 2 Fe 14 B crystals. 31 Accordingly, the composition and width of the boundary could impact the coercivity at N/R boundary locations 30 and could determine the magnetic domain wall energy at N/R boundary locations. 32 Here, the atomic arrangement of the Nd 2 Fe 14 B crystal that very close to the N/R boundary is necessarily distorted over a distance of typically 1 nm, which can be attributed to the redistribution of surface energy that would distort crystal lattice and create stacking faults.…”

“…Domain features in this work could be analyzed from the crystallographic information. For a single Nd 2 Fe 14 B crystal, easy axis is an alternative to extend domain branches 30 and to pin domain wall across twin boundaries. 39 Meantime, magnetic domain walls are strongly pinned at tilted crystals.…”

“…29 In this work, the 31°/[0 0 1] indicates the alignment between Nd 2 Fe 14 B crystals and the angular dependence of the coercive force. 14 In the case of a higher degree of misalignment, diffusion at boundary locations is a significant approach to enhance the coercivity, 33 especially when diffusion is made parallel to the texture axis of Nd 2 Fe 14 B crystals, 30 or when diffusion is made via replacing Nd with heavy rare earth elements (Dy or Tb). 34,38 During the anisotropic local hardening, diffusion channels are interrupted along the [0 0 1] easy axis (see Fig.…”

“…As an example, the development of remanence depends on the diffusion depth, which is anisotropic if parallel or perpendicular to the texture axis. 30,47…”

“…It has been well known that boundaries favor the nucleation of reversed domains, 2,30,31,40,42 while coupling that leads to the interaction domains is closely correlated to the boundary structures. 41 The preferred boundaries with specic misorientations might be repulsed by the domain wall, whereas the random boundaries might be attracted to the domain wall.…”