Diffusion induced precipitation along grain boundaries has been observed in Zn-coated NdFeB magnets. It was found that the volume diffusion of Zn through the matrix Nd2Fe14B grains is negligible. Zn penetrates into a thin outer layer of each Nd2Fe14B grain replacing Fe atoms in the Nd2Fe14B lattice and forming Nd-Fe-Zn (B) compounds. The displaced Fe moves to the boundaries, reacting with further Zn to produce Zn-Fe compounds. (C) 2002 Elsevier Science B.V. All rights reserved.
- grain boundaries