Cluster Dynamics Modelling of Guinier-Preston Zone Formation in Binary Al-Cu Alloys Derived from Cluster Expansion Energetics

We developed a multi-scale model for the precipitation of Guinier-Preston zones (GPZ) in Al-rich binary Al-Cu alloys. The approach is covering three length scales: (i) Starting from density functional theory (DFT) calculations a Cluster Expansion (CE) for the binary Al-Cu system on the fcc lattice is constructed. Based on the obtained CE (ii) a lattice Monte Carlo (MC) sampling technique, known as the overlapping distribution method, is used to calculate cluster free energies of Cu-clusters. Finally (iii) a meso-scale Cluster Dynamics (CD) model is constructed by taking the cluster free energies as input. The model is able to predict the evolution of size distributions of GPZ for different alloy compositions and ageing temperatures. To validate the model, kinetic MC simulations on the precipitation of GPZ are conducted. The results agree well with those obtained by our model.