Grain Size Mismatch Dependent Crack Blunting in Bimodal Materials

In this article, the crack passivation phenomenon associated with grain size mismatch in nanocrystalline (NC) materials with bimodal structure is extracted theoretically. By description, a portion of the dislocation emanating from the crack tip penetrates the grain boundary (GB). The calculated effective stress intensity factor indicates that the crack growth is inhibited. The suppression is related to the varying structures caused by grain size mismatch. Our results support the experimental results and provide a reasonable explanation that microcracks tend to grow and form in the nanocrystal matrix of bimodal Al. In addition, we extract GB misorientation effect on the crack blunting in bimodal materials. The study found that increasing the GB misorientation leads to the blunting of cracks in bimodal materials.