Abstract
The mechanical properties of materials depend on their structure. The influence of grain size and grain size distribution on the flow stress of polycrystalline materials (e.g. metals) has been widely reported. The value of the yield point is usually predicted by the Hall-Petch relationship which was established experimentally for micrometer grain sizes. When the grain size is reduced to the nanometric size, the relationship between grain size and flow stress changes for several reasons including activation of the mechanism of grain boundary sliding. Grain boundaries play a major role in the plastic deformation mechanism of polycrystalline nano-materials, because they possess a significantly large volume fraction of atoms at the grain boundaries. In order to quantitatively model this influence, a two-phase finite element model was developed using the generalized Hill potential theory for modelling the anisotropic plasticity of grain boundaries. The results of the numerical simulations give an insight into the influence of various parameters on the plastic deformation of nano-polycrystalline materials. The simulations were also applied to study the effect of grain size homogeneity on the mechanical properties of nanometals.