The highly symmetrical  = 3 (111) boundary was studied by means of high-resolution transmission electron microscopy, with a point resolution of 0.1nm. Quantitative image analysis showed that the Al atoms occupied the grain boundary plane. Marked relaxation led to a volume expansion of 0.08nm. Interstitial holes in the grain boundary structure, and the large expansion, were attributed to grain boundary weakness.

K.Nadarzinski, F.Ernst: Materials Science Forum, 1996, 207-209, 309-12