Samples with a sub- grain size were produced by means of intense plastic straining in torsion, and the grain boundary structures were studied by using high-resolution electron microscopy. It was found that the grain boundaries were usually curved or wavy along their length, and some portions exhibited regular or irregular arrangements of facets and steps. Grain boundary migration occurred so as to reduce the number of grain boundary facets and steps during high-energy electron irradiation. It was concluded that the observations demonstrated that the grain boundaries in the sub- grain size samples were in high-energy non-equilibrium configurations.

Z.Horita, D.J.Smith, M.Furukawa, M.Nemoto, R.Z.Valiev, T.G.Langdon: Materials Science Forum, 1996, 204-206, 437-42