Effect of ageing temper on the heat resistance of Al-Cu-Mg-Ag alloy with different compositions

Abstract

The size and number density of Ω phase significantly affect the heat resistance of Al-Cu-Mg-Ag alloys and the ageing temper was reported to affect the heat resistance of Al-Cu-Mg-Ag alloy by changing the size and distribution of Ω phase. In this study, the over ageing heat treatment has been confirmed to notably affect the heat resistance of different Al-Cu-Mg-Ag alloys even when the solute contents are significantly different. However, slight over ageing can enhance the heat resistance of the alloy, while sever over ageing will decrease that. By combining systematic statistical quantitative characterization with guidance from the KWN modeling, the critical size of Ω at high thermal exposure temperature ($r_{thermal}^{*}$) is clarified to be the key factor influencing the coarsening of Ω. The closer the size of Ω after artificial aging is to the $r_{thermal}^{*}$, the better the heat resistance of the alloy. Therefore, the heat resistance of the alloy can be improved by adjusting the aging process to tune the size of the Ω phase to be close to the critical size at service temperature.