Computational design of Al-Mg-Si alloy compositions and optimization of its heat treatment

Abstract

Currently, a major scientific and engineering hotspot lies in the synergistic enhancement of aluminum alloy properties through optimizing composition and heat treatment processes, aimed at both boosting performance and conserving energy. In 6xxx-series aluminum alloys, the interactions among the elements Mg, Si, Fe, and Mn excerts a great influence on the variants of AlFeSi phase and the transition of Mg 2 Si sub-strengthened phase. This work used thermodynamic and kinetic calculations to study the effects of Mg, Si, Fe, and Mn on the phase transitions of β-AlFeSi and Mg 2 Si in Al-Mg-Si alloys, and the results were verified experimentally. The computational results show that the elements Si, Fe, and Mn are important for the thermodynamic transformation of β-AlFeSi, and these elements interact with each other during this process. Furthermore, it is discovered that the Si content exerts a more pronounced impact on the precipitation of metastable phases compared to Mg, and it is essential for the full dissolution of the Mg 2 Si phase following homogenization and solution heat treatment. Among the investigated aging conditions, the alloy aged at 175 °C for 8 h reaches the peak-aged state and exhibits the highest strength, with a yield strength of 294.16±4 MPa, an ultimate tensile strength of 313.53±3 MPa, and a fracture elongation of 13.01±0.3%. The observed experimental results agree well with the predicted phase transitions and mechanical properties during the heat treatment process.