Effect of Cu Content on Microstructure and Mechanical Properties of Al-Cu-0.4Mg-0.6Ag Alloy

The effect of Cu content on the microstructure and mechanical properties of AlCu-0.4Mg-0.6Ag alloys is investigated by tensile testing,differential scanning calorimetry(DSC),scanning electron microscopy(SEM) and transmission electron microscopy(TEM).It is shown that the artificial aging process of the alloys is improved and the tensile strength is increased with the increase of the Cu content,Cu content from 4.0% increased to 8.0%,the tensile strength of the alloy is increased to 559MPafrom 434MPa at the room temperature,and to 228MPa from 141MPa at 300℃,respectively.The specific elongation of the alloy with 8.0% Cu is more than 9% at the room temperature.The coherent plate-like Ω phase and a small amount of θ′ phase are the predominant hardening phases in the Al-Cu-0.4Mg0.6Ag alloys at peak-aged stage at 185℃ and the quantity of the Ω phase is increased with the increase of the Cu content.The increase of the Cu content not only improves the solid solution strengthening effect,but also increases the content of θ(CuAl2)phase,which shows dispersion strengthening effect,so it is helpful to improve the high temperature performance of the alloy.