First principle calculations of pressure dependent yielding in solute strengthened aluminium alloys

Abstract

The pressure dependence of the yield stress in solute strengthened aluminium alloys is investigated by first principle calculations. The solute elements studied are magnesium, silicon and copper. A fixed boundary cluster model is employed to calculate the interaction energies between the edge dislocation and the solutes, while simultaneously controlling the hydrostatic pressure in the system. The results show a systematic increase in yield stress with increasing hydrostatic pressure for all solute elements. The calculated pressure dependence is in qualitative agreement with experiments, but underestimated quantitatively. It is suggested that the experimentally observed pressure dependence is caused by both the static and the transient dilatancy of dislocations. In contrast to magnesium and copper atoms, silicon atoms are found to interact non-elastically with dislocations within the core field, indicating that the favourable position for the silicon atoms is in the distorted sites in the matrix.