Prediction of diffusivities in fcc phase of the Al-Cu-Mg system: First-principles calculations coupled with CALPHAD technique

The diffusivities in fcc phase of the Al-Cu-Mg system are systematically predicted via first-principles calculations coupled with CALPHAD (CALculation of PHAse Diagram) technique. All the self- and impurity diffusion coefficients of fcc phase in this ternary system, including both stable and meta-stable states, are calculated via first-principles calculations. The enthalpy of vacancy formation and migration, binding enthalpy of vacancy-solute, entropy of vibration, effective atomic jump frequency, as well as the pre-factors and activation energies for diffusion in the Arrhenius equation are obtained. The atomic mobilities of the three elements are then obtained based on the first-principles calculated diffusion coefficients. Moreover, the interdiffusion coefficients of the Al-Cu, Al-Mg and Cu-Mg binary systems are calculated by means of the DICTRA (DIffusion-Controlled TRAnsformation) package in the framework of CALPHAD approach. Comprehensive comparisons between the predicted and measured diffusivities show that most of the experimental data can be well reproduced. It is found that the combination of first-principles calculations and CALPHAD technique is an effective strategy to obtain diffusivities for multicomponent systems.