The temperature dependence of internal grain-boundary friction in coarse- and ultrafine-grained Ti was investigated. It was demonstrated that true grain-boundary slipping causes internal grain-boundary friction in ultrafine-grained Ti, as in coarse-grained metals. It was established that when going from the coarse-grained structure with perfect grain boundaries to ultrafine-grained structure with imperfect grain boundaries, the temperatures of the beginning and intense development of true grain-boundary slipping decreased together with the activation energy of this process. The diffusion mechanism of true grain-boundary slipping was justified for both structural states.

True Grain-Boundary Slipping in Coarse- and Ultrafine-Grained Titanium. E.F.Dudarev, G.P.Pochivalova, Y.R.Kolobov, O.A.Kashin, I.G.Galkina, N.V.Girsova, R.Z.Valiev: Russian Physics Journal, 2004, 47[6], 617-25