Defect formation in Nd2Fe14B grains caused by Zn diffusion

Defect formation in Nd2Fe14B grains, caused by a low-pressure-pack-sublimation Zn coating process, has been investigated. The results indicate that, in the Zn-affected region, low-angle boundaries decorated with precipitates form within the Nd2Fe14B grains. Zn, which is almost insoluble in Nd2Fe14B, diffuses initially along the grain boundaries and it is then thought to cause extrinsic dislocations in the grain boundaries to migrate into the Nd2Fe14B grains, forming low-angle boundaries. The Zn diffuses along these low-angle boundaries and, when its concentration becomes high enough, it forms precipitates. The precipitates have a (possibly ordered) bcc-based structure with the basic bcc lattice parameter a approximate to 0.27 nm and a composition of approximately 77 +/- 5 at. % Fe, 11 +/- 2 at.% Nd and 12 +/- 5 at. % Zn.