The kinetics of clustering in Al Mg Si alloys studied by Monte Carlo simulation

The kinetics of clustering in Al Mg Si alloy is studied by Kinetic Monte Carlo KMC simulations. The simulations take into account the probability of vacancy jumping to nearest neighbour sites. This probability is calculated by considering both the activation energies for single vacancy migration and the difference of interaction energies before and after jumping. The simulations show that clustering in Al Mg Si is fast and takes place in three stages. In the initial stage, dimers, trimer and small co clusters form. The number density of such clusters increases rapidly and solute atoms aggregate to those clusters until a maximum density value is reached after 2 min. In the second stage from 2 min to around 100 min, a decrease of the number density of small clusters accompanied by an increase of the fraction of solute contained in all the clusters can be observed. Finally, coarsening of some of the clusters by coalescence was found, hence further reducing the cluster number density, while the amount of solute atoms in the clusters remains constant. We discuss how robust the results are with respect to changes of the input parameter