Multi-scale Cluster Dynamics modelling of Guinier-Preston zone formation in binary Al-Cu alloys

We developed a multi-scale model for the prediction of precipitation kinetics of binary alloys and present its application to the formation 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 precipitate clusters. Finally (iii) a meso-scale Cluster Dynamics (CD) model is constructed by taking the cluster free energies as input. The result is a fast, parameter free method that is able to predict the evolution of precipitate size distributions. To validate the model kinetic MC simulations on the precipitation of GPZ are conducted. The results agree well with those obtained by our model. When comparing our results to experimental data a problem of time scaling arises, which is discussed in the results section. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.