Co-segregation effect of Si and Zr at Al/L12–Al3Sc interface

Abstract

Reducing the usage of Sc element, as well as improving the thermal stability of nano-precipitate L12–Al3Sc are critical in expanding the application field of Al–Sc based alloys. Previous experiments showed that the impurity Si plays a leading role in accelerating the precipitation and strengthening the thermal stability of Al–Sc-Zr alloy, but the micro mechanism of these effects are not be given at atomic and electron scale. Herein, we performed a first-principles calculations to focus on the segregation behaviors of Si and Zr at Al (001)/L12-Al3Sc (001) interface. The results show that the ahead segregated Si atom, which prefers to occupy the Al site of Al3Sc precipitate side, contributes to induce Zr substituting the Sc atom that is the nearest neighbor of Si rather than the Sc site in Al matrix side. A quantitative calculation suggests that the reduction of Sc usage can at least reach 12 % as the concentration of added Si in Al bulk is about 0.06 %.