In recent years, Aluminum (Al) alloys have garnered significant attention in the scientific community due to their exceptional strength-to-weight ratio, making them ideal candidates for aerospace applications. The incorporation of Lithium (Li) into the well-studied Aluminum-Copper (Al-Cu) system results in a decrease in density and the formation of a diverse array of precipitates that contribute to the material's dispersion strengthening. However, Al-Cu-Li alloys present challenges in terms of weldability, making them difficult to handle in fusion-based processes. As such, solid-state processes are more suitable, where the peak process temperatures are kept below the bulk melting point of the processed alloy. Al-Cu-Li alloys exhibit high tensile strength, improved high cycle fatigue and fatigue crack growth resistance. The Cu/Li ratio plays a crucial role in determining the mechanical properties of the alloy, as it governs the thermodynamic equilibria of the phases and the precipitation sequence. The size, frequency and morphology of these precipitates are dependent on thermodynamics and diffusion kinetics.

This study aims to investigate the quantitative influence of Cu and Li concentrations on the precipitation behaviour in this alloy class through the utilization of a coupled Cahn-Hilliard and Allen-Cahn phase-field model that is discretized using a finite-element formalism. The precipitation behaviour is captured by incorporating anisotropy in the interfacial energy and the elastic contribution, derived from DFT calculations, to the total free energy. The model is numerically implemented using the deal.II library, providing efficient numerical solution schemes and an adaptive meshing algorithm. Additionally, the phase-field method is coupled with the CALPHAD framework to determine thermodynamic free energies and kinetic parameters.