Growth of Ω Plates and Its Effect on Mechanical Properties in Al-Cu-Mg-Ag Alloy with High Content of Silver

In this study, the effects of thermal exposure at 200 °C on the mechanical properties and the growth of Ω plates in an Al-Cu-Mg-Ag alloy with high content of silver were investigated. It was shown that the tensile strength of the exposed alloy decreased with the increase of the mean lengths of Ω precipitates and the decrease in the volume fraction of the Ω phase. The decrease in tensile strength of the 165 °C/14-h-aged samples was less significant than that of 165 °C/2-h-aged samples because the lengthening rate of Ω plates was lower and the number density of Ω precipitates was higher in the 165 °C/14 h-aged samples. The thickening rate of Ω plates was very low during exposure at 200 °C because of high content of silver, and the growth behavior was caused mainly by the lengthening of Ω plates within the habit plane. High content of silver inhibited the thickening of Ω plates and promoted the lengthening of Ω precipitates during exposure.