Effect of aging route on the precipitation behavior and thermal stability of Al–Cu–Mg–Ag alloy

In this study, the evolution of Ω plates during artificial aging and the effect of peak-aging treatment and over-aging treatment on the thermal stability of Al–Cu–Mg–Ag alloy were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was shown that the diameter distribution of Ω plates in the over-aged sample was narrower compared to the peak-aged one, which suppressed the Ostwald ripening in the over-aged sample. In addition, the Ω plates in the over-aged sample has a larger aspect ratio than that in the peak-aged sample, which makes it more likely for the soft impinge to inhibit the growth of the Ω plates. Quantitative analysis showed that after heat exposure, Ω plates in the over-aged sample contributed more to the yield strength compared to peak-aged sample. This study shows that better thermal stability can be obtained in exchange for a little loss of room temperature mechanical properties, improving the application potential of Al–Cu–Mg–Ag alloys.