Dislocation-Solute Cluster Interaction in Al-Mg Binary Alloys

The close-range interaction of dislocations and solute clusters in the Al-Mg binary system is studied by means of atomistic simulations. We evaluate the binding energy of dislocations to the thermodynamically stable solute atmospheres that form around their cores, at various temperatures and average solid solution concentrations. A measure of the cluster size that renders linear the relationship between the binding energy and the cluster size is identified. It is shown that as the temperature increases the representative cluster dissolves following an Arrhenius law. The corresponding activation energy of this process is found to be independent of the average solute concentration. The variation of the interaction energy between a dislocation and a cluster residing at finite distance from its core is evaluated and it is shown that the interaction is negligible once the separation is larger than approximately 15 Burgers vectors. The data are relevant for the dynamics of dislocation pinning during dynamic strain ageing in solid solution alloys and for static ageing.