High-resolution electron microscopy was used to examine the structural features of grain boundaries in solid solution alloy samples which had been produced with sub-micron grain sizes by using an intense plastic straining technique. The grain boundaries were mainly curved or wavy along their length, and some portions were corrugated, with regular or irregular arrangements of facets and steps. During exposure to high-energy electrons, grain boundary migration occurred so as to reduce the number of facets and thus reduce the total boundary energy. The observed features conclusively demonstrated that the grain boundaries in these sub-micron grained materials were in a high-energy non-equilibrium configuration.

Z.Horita, D.J.Smith, M.Furukawa, M.Nemoto, R.Valiev, T.G.Langdon: Journal of Materials Research, 1996, 11[8], 1880-90