Improvement of high-temperature strength of Al-4.5Cu alloys by Sc addition through thermally stable phase

The microstructure and high-temperature mechanical properties of Al-4.5Cu alloy, and alloys with Sc addition of 0.1%, 0.2%, and 0.4% were studied. The addition of Sc generates high-temperature stable phase – W phase along the grain boundary, which consumes Cu in the matrix and decrease the θ′ after T6 treatment. However, Sc stabilizes the θ′ precipitate during 300°C exposure and contributes to the high temperature strength by Orowan mechanism. The high-temperature performance of Al-4.5Cu alloy is improved and the strength first increases and then decreases with increasing content of Sc, with optimal content of Sc being 0.2%. The tensile strength of 0.2%Sc alloy at 300°C reaches 158 ± 3 MPa, which is 28 ± 3 MPa higher than that of Sc-free alloy.