A study was made of the transmission of cooperative grain boundary sliding. Tri-crystals of 5N-purity material, with high-angle boundaries, were used. It was concluded that the main requirements for the self-organization of cooperative grain boundary sliding were that boundaries with the maximum Schmid factor should be selected among the various available boundaries. Among these, boundaries with the longest-range areas and minimum misorientations were preferred. A reduction of the critical stress, due to the stimulation of grain boundary sliding by intragranular slip, could contribute to the cooperation process. Because the theoretical analysis which was used here was simplified, it was not possible to detect a definite direction for local migration. However, on the basis of the experimental observations, it was concluded that the direction of migration was determined by non-symmetry of an elastic stress field at the triple junction. One particular cause of such non-symmetry was suggested to be partial stress relaxation during the initiation of grain boundary sliding along the adjacent boundary. In other cases, a chain of consecutive processes could occur. The stress which was generated by the head of the pile-up initiated sliding along the adjacent boundary, where the resolved stresses which arose from the external stress were insufficient.

V.V.Astanin, A.V.Sisanbaev, A.I.Pshenichnyuk, O.A.Kaibyshev: Scripta Materialia, 1997, 36[1], 117-22