Microstructure evolution and mechanical properties of the Al-Cu-Mg-Ag alloy during non-isothermal aging

In this work, the effect of non-isothermal aging treatment with the heating rate of 20, 40 and 60 °C/h on the precipitation behavior and mechanical properties of the Al-Cu-Mg-Ag alloy were investigated by differential scanning calorimetry (DSC) analysis, transmission electron microscopy (TEM) and high-angle annular dark field – scanning transmission electron microscopy (HAADF-STEM) observation, as well as hardness and tensile tests. The activation energy and Avrami exponent associated with the precipitation of Ω phase were calculated based on the non-isothermal DSC experiments with various heating rates. The size distribution and number density of Ω plates in the α-Al matrix under peak-aged condition were quantitatively counted. Besides, A non-isothermal aging kinetics model proposed was applied to evaluate the heating aging treatment (HAT) process of the Al-Cu-Mg-Ag alloy. Results indicate that HAT modifies the size and density of Ω phase, thereby enhancing the mechanical properties of the Al-Cu-Mg-Ag alloy. HAT promotes the precipitation of Ω phase and shortens the aging time for the alloy to reach the peak-aged condition. It is interesting that the size distribution of Ω plates shifts to larger values with the increase of the heating rate during the HAT process.