Effects of Sc addition on the microstructure and mechanical properties of cast Al-3Li-1.5Cu-0.15Zr alloy

Effects of Sc addition on the microstructure and mechanical properties of cast Al-3Li-1.5Cu-0.15Zr alloy were investigated by microscopy methods and tensile tests. With the addition of 0.15 wt% Sc, the grain size of studied alloy in as-cast state decreased from 120 µm to 30 µm and did not grow obviously after two-step solution treatment (32 h at 500 °C+24 h at 560 °C). After aging at 175 °C for 32 h, the elongation (EL) of Sc-containing alloy reached 5.5%, which increased by 83% compared with Al-3Li-1.5Cu-0.15Zr alloy. The key factors for improvement of comprehensive mechanical properties in Al-3Li-1.5Cu-0.15Zr-0.15Sc alloy could be summarized as follows: grain refining, size reduction of δ' phases and the precipitation of core/double-shell Al3 (Li, Sc, Zr) composite particles.