The asymmetrical tilt  = 5 [001]/(310) grain boundary was studied in samples which had been prepared by cold-rolling and annealing. Measurements of the Mg concentration in the bulk, and at grain boundaries, indicated variations in the Mg content which ranged from 4 to 11at%. This variation was attributed to a local ordering of the Mg atoms. High-resolution electron microscopy revealed that the boundary ran parallel to the median of (310), and contained segments that were composed largely of 2 types of structural unit. One unit contained 7 atomic sites, while the other contained 8 sites. In both types of unit, the grain boundary coincident-site lattice was contiguous across the interface and exhibited a periodicity in its core structure. The latter was characterized by so-called kite-like structural units which contained 7 atoms, and agreed well with the structure of  = 5 grain boundaries in pure face-centered cubic materials. The presence of atomic-scale ordering of Mg atoms along the boundary core was associated with the existence of the structural unit with 8 atomic sites.

M.Shamsuzzoha, I.Vazquez, P.A.Deymier, D.J.Smith: Interface Science, 1996, 3[3], 227-34