In this study, effect of copper and silicon content on the mechanical properties of Al-Cu-Si-Mg alloys has been investigated. Al-Cu-Si-Mg alloys with 1, 3, 4.5, 6% Cu and 0, 5, 7, 12, 18% Si were utilized for this purpose. After melting and Na modification, alloys were cast in metal molds at 780 degrees C and solidified. They were solution treated at 490 degrees C for 4h and then quenched. Samples were aged at 180 degrees C for 5, 10, 15, 20 h to observe the effect of aging on mechanical properties. (c) 2005 Elsevier B.V. All rights reserved.