Influence of Cu on microstructure and tensile properties of 7XXX series aluminum alloy

The effect of copper content on tensile properties and microstructure of 7XXX series aluminum alloys at 90% deformation is investigated by tensile test, optical microscopy, scanning electronic microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that higher Cu-containing alloy would precipitate more quantity of second-phase particles in rolling process at 420 degrees C, which facilitates the process of recrystallization during solution treatment. With the increase of copper content from 0 to 1.6 wt.%, the density of c' phase and the degree of recrystallization increase, meanwhile the strength and plasticity of Al-Zn-Mg-Cu alloy are improved in T6 heat treatment. In addition, the tensile fracture of Cu-free alloy belongs to quasi-cleavage fracture, while the tensile fracture of Cu-containing alloy is dimple fracture and the number of dimples increases with the increasing of copper content. (C) 2014 Elsevier Ltd. All rights reserved.