Heat Treatments for Precipitation of Scandium-Containing Dispersoids in an Si-Containing Aluminum Alloys

Benefits of alloying Sc with aluminum resulting from the precipitation of coherent Al3Sc dispersoids, including refined microstructure, increased strength, and improved weldability, have been demonstrated for a number of commercial aluminum alloys. Historically interactions between Sc and Si have limited the benefits of Sc additions in Al-Mg-Si 6xxx alloys. The first step towards developing a Sc containing 6xxx-alloys requires studying the interaction between Si and Sc. Hence, this work characterizes the aging response associated with precipitation of Si-modified Al3Sc dispersoids in a Sc-containing Al-Si alloys. The work reported in this paper focuses on understanding the breakdown of the solid solution of Sc in Si-containing aluminum alloys. Results of this study can be used to define heat treatment schedules for scandium containing 6xxx alloys.