Effects of Sc on the vacancy and solute behaviours in aluminium

Abstract

Element Sc is a promising candidate for optimizing the high-temperature mechanical properties of Al alloys. In this study, the Sc-solute, Al3Sc-vacancy and Al3Sc-solute interactions in aluminium are investigated extensively by using first-principles calculations. The correlation between the various interaction energies and the solute atomic size, and the Sc-solute compound formation energy has been evaluated. A negative correlation between the first nearest neighbour Sc-solute binding energies and the lowest Sc-solute compound formation energies has been identified, while the second nearest neighbour Sc-solute binding energies increase monotonically with the solute atomic size. Al3Sc precipitates can bind vacancy strongly at the specific atomic site, but their relatively low number density limits their influence on vacancy behaviours during the ageing period shortly after quenching. Compared to the atomic size, the trend for solute segregating at the interface between Al3Sc precipitate and Al bulk is more strongly related to the Sc-solute binding energy. The calculated results can clarify the available experimental observations for Al-Sc, Al-Cu, Al-Mg-Si and Al-Zn-Mg-Cu alloys, and it is hoped to guide the design of high-performance Al alloys.