Effects of Ag addition on the microstructures and properties of Al–Mg–Si–Cu alloys

Abstract

Effects of Ag addition on the microstructures, aging characteristics, tensile properties, electrochemical properties, and intergranular corrosion (IGC) properties of Al–1.1Mg–0.8Si–0.9Cu–0.35Mn–0.02Ti alloy were investigated using scanning electronic microscopy and transmission electronic microscopy. The aging process of Al–Mg–Si–Cu alloys was accelerated by the addition of Ag. The strength of peak-aged Al–Mg–Si–Cu alloys was enhanced by Ag addition because of the high density of β″- and L-phase age-hardening precipitates. The corrosion performance of the Al–Mg–Si–Cu alloy is closely related to the aging conditions and is independent of the Ag content. The IGC susceptibility is serious in the peak-aged alloy because of the continuous distribution of Cu-rich Q-phase precipitates along grain boundaries. Ag addition reduces the size of the grain-boundary-precipitate Q phase and the width of the precipitate-free zone and thus results in decreased IGC susceptibility of Al–Mg–Si–Cu alloys.