A preliminary study on optimizing the heat treatment of high strength Al–Cu–Mg–Zn alloys

The design of critical aerospace alloys is primarily built on optimizing strength and ductility, both of which can be enhanced by controlling the alloying element additions as well as heat treatment conditions. The 7075 alloy is one such aerospace alloy. The main objective of this study was to optimize the 7075 strength. Several experimental alloys were prepared and tensile test bars were cast using an ASTM B-108 type permanent metallic mold. The as-cast samples were then solution heat-treated at 470 °C for times up to 48 h. The solution heat-treated bars were also aged in order to improve the alloy strength through precipitation hardening. Line scans for Mg, Cu and Zn were obtained from the various heat-treated alloy samples using an electron probe microanalyzer equipped with Energy Dispersive X-ray (EDX) and Wavelength Dispersive Spectroscopic (WDS) facilities. Peaks corresponding to the Mg, Cu and Zn concentrations in the as-cast samples disappeared after solution treatment, reflecting optimized homogeneity structures. The newly developed versions of the 7075 alloy displayed an ultimate tensile strength (UTS) of ∼1 GPa. - Highlights: • Optimize 7075 alloy strength using proper additives, deformation, heat treatment. • With proper casting/heat treatment, alloy can reach ∼1 GPa UTS and 5–8% elongation. • Fracture controlled by Fe, Cu, Mg intermetallics present after applied heat treatment