Simulation of the evolution of GP zones in Al–Cu alloys: an extended Cahn–Hilliard approach

Abstract A kinetic model, based on the approach given by Cahn and Hilliard, was applied for a simulation of the formation and growth of Guinier–Preston (GP) zones in Al–Cu alloys. Thermodynamic data were provided by the CALPHAD method for the metastable phases to warrant for simulation of real Al–Cu alloys. The classic Cahn–Hilliard equation was extended to include the anisotropic elastic strain energy, which determines the morphology of GP zones. The model was applied to a simulation of spinodal decomposition cCu0=0.06 and precipitation of an alloy with concentration cCu0=0.02 which is beneath the maximum solubility. The latter simulation was carried out assuming pre-existing nuclei since the Cahn–Hilliard model does not include any mechanism for nucleation. The results (length and thickness of the precipitates) were in good agreement with experiments.