Effect of Ag on the precipitation stability in Al-Mg-Si-Ag alloy: First-principles calculations, CALPHAD modeling and experimental validation

Title : Effect of Ag on the precipitation stability in Al-Mg-Si-Ag alloy: First-principles calculations, CALPHAD modeling and experimental validation

Abstract:

Al-Mg-Si-Ag alloys offer a desirable balance between formability and bake-hardening potential, making them attractive for advanced engineering applications. However, complete crystal structure information of precipitate phases is not always available or unambiguous. Thus, the Gibbs free energy of different phases in the Al-Mg-Si-Ag alloy system was determined by combining first-principles calculations, cluster expansion method and Monte Carlo simulations. This information was used to develop a thermodynamic database of the Al-Mg-Si-Ag system, enabling accurate determination of phase stability and phase distribution. The results revealed that the addition of Ag significantly modifies solute clustering behavior and promotes the formation of Guinier-Preston zones at the early stages of the precipitation in Al-Mg-Si-Ag alloys. In contrast, the crystal structure of the β″ strengthening phase was not influenced by the presence of Ag. The developed TDB for this quaternary alloy will facilitate the prediction of thermodynamic properties in binary and ternary systems involving Al, Mg, Si and Ag atoms. It also provides a robust foundation for extrapolating more complex Al-Mg-Si-based alloy systems.

Biography:

Wei Shao is a Postdoctoral Researcher at Warsaw University of Technology. She received her PhD in Materials Science from the Polytechnic University of Madrid and IMDEA Materials Institute, as well as holds a PhD from Yanshan University, China. Her research interests include first-principles calculations, phase diagram prediction, and thermodynamic modeling of alloys. Her recent work focuses on the effect of Ag on the precipitation stability of Al-Mg-Si-Ag alloys, combining first- principles and CALPHAD approaches.