Effect of Cu, Zn, and Mg Concentration on Heat Treating Behavior of Squeeze Cast Al-(10 to 12)Zn-(3.0 to 3.4)Mg-(0.8 to 1)Cu

Aluminum Alloy AA-7034 is a high strength wrought alloy with reasonable ductility containing 10-12 wt% Zn, 2-3 wt% Mg, and 0.8-1.2 wt% Cu. This work investigates the effect of varying the concentration of Zn (10-12 wt%) and Cu (0.8-1 wt%) on the solutionizing and aging behavior of squeeze cast AA-7034 samples. The same behaviors were investigated when Mg content was increased beyond 3 wt%. The solutionizing heat treatment dissolved much of the macroscopic second phases present in the as-cast AA-7034 alloys, but a significant amount of second phases remain after solutionizing in alloys with >3 wt% Mg. The behaviors of the various Al-Zn-Mg-Cu alloys are compared to squeeze cast Al-A206 casting alloy heat-treated to the T7 condition. All Al-Zn-Mg-Cu alloys obtained higher hardness values than those obtained by Al-A206-T7.