The investigation of precipitation processes in modern aluminium alloys plays an important role for the design of many material properties, like for example strength or corrosion resistance. The influence of ageing time and temperature therefore constitutes the key for a quantitative understanding of precipitate formation.
The prediction of the evolution of the precipitate size distribution is a powerful tool for the characterisation of an alloy temper state. We developed a multi-scale model for the precipitation of early stage precipitates in binary Al-Cu alloys, the so-called Guinier-Preston zones (GPZ). The approach is covering three length scales: Starting from density functional theory calculations a Cluster Expansion for the binary Al–Cu system is constructed. Based on the obtained Cluster Expansion a lattice Monte Carlo sampling technique, known as the overlapping distribution method, is used to calculate cluster free energies of Cu-clusters. Finally a meso-scale Cluster Dynamics 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 Monte Carlo simulations on the precipitation of GPZ were conducted and the results agree well with those obtained by our model.