Abstract: The effect of Si on the microstructure and mechanical properties of binary Al-4.5%Cu alloy has been investigated. The results show that the addition of Si does not have any effect on alloy strength; however, it decreases the ductility of the as-cast Al-4.5%Cu alloy. It is obvious that after T4 heat treatment, the microstructure and mechanical properties of Al-4.5%Cu-Si alloys are improved, especially for the alloy with an Si addition of 2%.

Key words: Al-Cu alloy, Si, heat treatment, mechanical property