A simple dislocation model of deformation resistance of ultrafine-grained materials explaining Hall–Petch strengthening and enhanced strain rate sensitivity

A model is presented where the properties of ultrafine-grained (UFG) materials are explained in terms of the influence of high-angle boundaries on the rates at which dislocations are stored and recovered at the boundaries. The model reproduces the experimental observations that UFG materials reach a steady state where the deformation resistance is independent of strain, that the strain rate sensitivity of flow stress is relatively high and that the steady-state flow stress increases inversely with the square root of grain size. The model results are compared to experimental data for UFG Cu and nanostructured Ni.