Investigation of Evolution of Microstructure, Mechanical Properties, and Corrosion Resistance of Novel Al-Mg-Si-Ag Alloy

In this paper, the evolution of the microstructure, mechanical properties, and intergranular corrosion (IGC) resistance of an Al-Mg-Si-Ag alloy is systematically investigated. For the as-cast alloy, the microstructure consists of the Mg2Si phase and Mg32(Al, Ag)49 phase. In the isothermal aging process, the novel alloy presents a significant age hardening effect. The ultimate tensile strength (UTS) and yield strength (YS) of the peak-aged alloy are 342 MPa and 231 MPa, respectively, which are 53 MPa and 84 MPa higher than that of the as-quenched alloy. The main strengthening phase at the peak-aged stage of the alloy is the MgAg phase, which has a body-centered cubic structure with a lattice constant of a = 0.33 nm. In addition, the IGC resistance of the peak-aged alloy is worse than that of other aged alloys. The corresponding microstructure of GBPs of the peak-aged alloy is more consecutive, and this is the main reason for the deterioration of IGC resistance of the alloy.