Effects of alloying elements on the amounts of MgZn2 and S-Al2CuMg phase in 7075 aluminum alloy

Thermodynamic equilibria of 27 compositions of 7075 aluminum alloy are computed using JMatPro. The maximum amount of MgZn2 phase (MP[M]) and the maximum amount of S-Al2CuMg phase (MP[S]) in each composition are taken as the objective functions. Effects of the contents of Zn, Mg and Cu on MP[M] and MP[S] are studied using analysis of variance (ANOVA) with second-order interactions. Analysis results suggest that Zn, Mg, Cu, Zn[Formula: see text]Mg and Mg[Formula: see text]Cu have a significant influence on the MP[M] with a sequence of Zn[Formula: see text]Mg[Formula: see text]Mg[Formula: see text]Cu[Formula: see text]Cu[Formula: see text]Zn[Formula: see text]Mg, whereas Zn, Mg and Cu have a significant influence on the MP[S] with a sequence of Cu[Formula: see text]Zn[Formula: see text]Mg. Predictive equations for calculating the amounts of MP[M] and MP[S] are obtained using regression analyses. With the requirement of maximum amount of MP[M] and minimum amount of MP[S] within the alloy, the optimized composition of 7075 aluminum alloy is predicted and it contains 6.1%Zn, 2.27%Mg and 1.2%Cu.