Transmission electron microscopy was used to study the defect structure of ultra-fine grained samples which had been produced by severe plastic deformation. The first evidence was found, for the presence of a high density of partial disclinations in grain boundaries, by using direct structural methods. The density of these defects was measured by using a specially developed method of electron-microscopic analysis for structures with a high lattice curvature.

Electron-Microscopic Investigation of Grain Boundaries in Ultra-Fine Grained Nickel Produced by Severe Plastic Deformation. A.N.Tyumentsev, J.P.Pinzhin, A.D.Korotaev, M.V.Tretyak, R.K.Islamgaliev, R.Z.Valiev: Physics of Metals and Metallography, 1998, 86[6], 604-10