Molecular dynamics simulation of grain boundary geometry on crack propagation of bi-crystal aluminum

Grain boundaries are known to be one of the major microstructural barriers to short crack growth in most metallic materials. In this paper, effects of specified twist angle and tilt angle of grain boundary (GB) on the crack propagation and growth rate of bi-crystalline aluminum have been investigated with the molecular dynamics method. The results show that the resistance of high angle twist GB to crack propagation is much larger than that of tilt GB, due to the propagation in the GB region and the change of crack direction. The dislocations may move owing to the stress distribution in the front area of crack, resulting in the migration of low angle grain boundaries, regardless of twist angle or tilt angle. The results also indicate there is a strong relationship between stress and crack propagation stage. In general, the crack propagation and growth rate is more sensitive to twist angle of GB.