Toughening of nanocrystalline materials by nanograin rotation

Nanograin rotation has been identified by scientists as a general mode of grain growth in nanocrystalline materials. However, how does nanograin rotation modulate the fracture toughness is an unsolved problem. Here we developed a theoretical model to investigate the effect of nanograin rotation on crack growth behavior in a nanograined specimen. A rotation parameter is defined to represent the level of rotation. Our findings show that the fracture toughness increases linearly with the rotation parameter, i.e., the stronger the rotation, the higher the fracture toughness. Moreover, the fracture toughness can be maximized by modulating the orientation of the grain boundary that separates the two rotated grains. As a result, a high fracture toughness can be achieved, which indicates that the rotation process can serve as an effective toughening mechanism in nanocrystalline materials.