A theoretical model was suggested which described the yield-stress dependence upon grain size in fine-grained materials. It was based upon a competition between conventional dislocation slip, grain-boundary diffusional creep (Coble creep) and triple-junction diffusional creep. In the framework of this model, the contribution of diffusional creep mechanisms to plastic deformation increased with a reduction of grain size; causing an abnormal Hall¯Petch dependence in the range of small grains. A grain-size distribution was incorporated in order to account for the distribution of grain sizes which occurred in real specimens. The results of the model were compared with experimental data on Cu, and were shown to be in good agreement.

Triple Junction Diffusion and Plastic Flow in Fine-Grained Materials. A.A.Fedorov, M.Y.Gutkin, I.A.Ovidko: Scripta Materialia, 2002, 47[1], 51-5