The effect of various RRA treatments on the strength and corrosion behavior of a new type of Al–Zn–Mg–Er–Zr alloy

Abstract

AbstractThe effect of various retrogression and reaging (RRA) treatments on the strength and corrosion behavior of a new type of Al–Zn–Mg–Er–Zr alloy has been investigated by hardness testing, tensile testing, and evaluating the intergranular corrosion (IGC) and exfoliation corrosion (EXCO) behavior. The results show that the RRA treatment can effectively improve the IGC and EXCO resistance by sacrificing less strength due to the formation of grain interior precipitates and the grain boundary precipitates similar to the T6 temper and T73 temper, respectively. At the peak value of the hardness, the alloy retrogressed at 190°C shows the better IGC and EXCO resistance; the alloy retrogressed at 170°C exhibits the higher strength. The optimal combination of strength, IGC and EXCO resistance is obtained after retrogression at 180°C for 60 min. For the different heat‐treatment tempers, the corresponding microstructure evolution of the precipitates, including Al3(Er,Zr) particles is discussed in detail.