Modeling of dislocation patterns of small- and high-angle grain boundaries in aluminum

A molecular dynamics simulation approach to the investigation of grain boundary structures is presented. By the example of aluminum crystallization from the melt we demonstrate the formation of polycrystalline structures from coexisting nucleation seeds. The latter are used to induce specific crystallographic orientations and hence determine the tilting of the grains resulting from further crystal growth. This allows the systematic investigation of the evolution of grain boundary structures as a function of the tilt angle. On this basis, the transition from small- to high-angle grain boundaries in aluminum as obtained from rapid under-cooling of the melt is rationalized by arrays of two different sets of dislocation pairs.