Atomistic determination on stability, cluster and microstructures in terms of crystallographic and thermo-kinetic integration of Al-Mg-Si alloys

Nanoscale-sized precipitates are directly tied to the strength and ductility of heat-treatable Al-Mg-Si alloys, thus understanding the precipitation is crucial in adjusting and optimizing their mechanical properties. In this work, precipitation behaviors of the primary strengthening phases in Al-Mg-Si alloys are investigated in light of the crystallographic, thermodynamic and kinetic analysis. The structural stability and atomic clusters of the precipitated phases are analyzed by energetic computation and central force field cluster model. The precipitation microstructures and interfacial configurations are characterized by high-resolution transmission electron microscopy. These results are then used as essential inputs for the atomistic calculations at both ground state and finite temperatures to understand the morphological formation. Accordingly, the size evolution of the primary strengthening phase is obtained within a modelling framework and compared with the microstructure data measured from experiments. Furthermore, an underlying thermo-kinetic correlation behind the precipitation is analyzed in combination with tensile properties. Our investigation offers an insight into understanding the connection among thermo-kinetics, microstructures, and mechanical properties of Al-Mg-Si alloys, and thus will provide a theoretical guidance for developing alloys with desirable strength-ductility combination.