A synergetic grain growth mechanism uniting nanograin rotation and grain boundary migration in nanocrystalline materials

A theoretical model has been developed to analyze the energetic characteristic of a cooperative grain growth process in nanocrystalline materials. We proposed that the process can be realized by rotating the adjoining grains first and then migrating the boundary that separates the grains, or vise versa, or by enabling both rotation and migration simultaneously. It is revealed that the synergetic process is energetically more favorable than the pure individual growth processes, i.e., nano-grain rotation or shear-coupled migration of grain boundaries. The critical stress that is required to initiate the growth process is also considerably reduced. The findings suggest a new general mode of grain growth in nanocrystalline metals.