Significantly enhanced crack blunting by nanograin rotation in nanocrystalline materials

Experiments have shown that stress-driven grain growth is closely related to the enhanced crack growth resistance and the exceptional tensile ductility as observed in several nano-metals. However, the quantitative correlation remains unsolved. Here we developed a theoretical model to investigate the effect of nanograin rotation, one of the main modes of stress-driven grain growth, on dislocation emission from the tip of a semi-infinite crack in a nanograined solid. Our findings show that the nanograin rotation can significantly enhance the capability of the crack to emit dislocations, thus leading to strong crack blunting in nanomaterials.