Effect of solution-treating temperature on the intergranular corrosion of a peak-aged Al-Zn-Mg-Cu alloy

The effect of solution-treating temperature of 465-495 degrees C on the intergranular corrosion (IGC) susceptibility of the peak-aged Al-Zn-Mg-Cu alloy (7050) is investigated. The accelerated corrosion test results show that the IGC susceptibility first decreases and then increases with increasing the solution-treating temperature. Whereas, an opposite change is observed for the Cu content in grain boundary eta-Mg(Zn,Cu)(2) precipitates based on the quantitative measurement and modeling of grain boundary segregation and precipitation. Furthermore, the change in IGC susceptibility is explained by the electrochemical microcouples between grain boundary eta-Mg(Zn,Cu)(2) precipitates and precipitation-free zones (PFZs), of which the driving force varies with the Cu content in the eta-Mg(Zn,Cu)(2) precipitates due to different solution-treating temperatures. (C) 2020 The Author(s). Published by Elsevier B.V.