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

Abstract The effect of solution-treating temperature of 465–495 °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 η-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 η-Mg(Zn,Cu)2 precipitates and precipitation-free zones (PFZs), of which the driving force varies with the Cu content in the η-Mg(Zn,Cu)2 precipitates due to different solution-treating temperatures.