Effects of Yb and Zr microalloying additions on the microstructure and mechanical properties of dilute Al–Sc alloys

Abstract

It is known that Zr and Yb partition to the Al3Sc precipitates created during aging when microalloyed separately in dilute binary Al–Sc alloys. Addition of Zr delays precipitate coarsening, thereby improving the coarsening resistance of the ternary Al-Sc-Zr alloys. Addition of Yb increases the resistance against dislocation climb, thereby improving the creep resistances of the ternary Al-Sc-Yb alloys. A combination of microhardness, creep, and atom probe tomography measurements provide evidence that these effects of Zr and Yb additions are cumulative in quaternary dilute Al–Sc–Yb–Zr alloys: Yb increases their creep resistance at 300°C compared with ternary Al–Sc–Zr alloys and Zr improves their coarsening resistance at 300°C compared with ternary Al–Sc–Yb alloys. Additionally, excellent coarsening resistance is observed at 350 and 375°C.