A Computational Model for Intergranular Fracture in Nanocrystalline and Ultra-Fine Polycrystalline Metals

By means of finite element method which is based on the conventional theory of mechanism-based strain gradient plasticity, cohesive interface model is used to study the intergranular fracture in polycrystalline metals with nanoscale and ultra-fine grains. A systematical study on the overall strength and ductility of polycrystalline aggregates which depend on both grain interiors and grain boundaries for different grain sizes is performed. The results show that the overall strength and ductility of polycrystalline aggregates with nanoscale and ultra-fine grains are strongly related to the competition of grain boundaries deformation with that in grain interiors. Finally, the deformation and failure behavior of nanocrystalline nickel are described by using the computational model.