Dislocation sources and the flow stress of polycrystalline thin metal films

Plastic deformation of thin metal films has been investigated with the help of a discrete dislocation dynamics simulation. In particular, the operation of a Frank-Read source was studied in the confined geometry of a thin polycrystalline film. The results lead to a new model for the dependence of flow stress on film thickness and grain size. It is based on the assumption that the number of dislocation sources per grain is small and multiple activation is required. The model predicts a flow stress that scales with the inverse film thickness or grain size (whichever is smaller) and that is roughly four times higher than predicted by previous models, thereby giving better agreement with experimental data.