Effect of Thermal-Cold Cycling Treatment on the Microstructure and Corrosion Resistance of 7075-T83 Aluminum Alloy

Abstract

The enhancement of the mechanical properties of an alloy is often accompanied by a decrease in corrosion resistance. Therefore, in this paper, thermal-cold cycling (TCC) treatment was used to process 7075-T83 aluminum alloy to improve its corrosion resistance on the basis of ensuring its mechanical properties. Intergranular corrosion (IGC) and electrochemical tests combined with transmission electron microscopy observation were carried out to investigate the effect of TCC treatment on the microstructure and corrosion resistance of the 7075-T83 aluminum alloy. The results showed that the corrosion resistance of the alloy was significantly improved and the microstructure was well optimized after two TCC treatments. The IGC depth of the alloy was the shallowest, at 25.8 μm, and the corrosion current density and corrosion rate reached the minimum values of 0.00148 mA/cm² and 0.0484 mm/a, respectively. In addition, the average diameter of the matrix precipitates was the smallest, the volume fraction was the highest, the thickness of the passive film formed on the surface of the alloy was the thickest, reaching 3.81 nm, which effectively resisted the erosion of Cl⁻, while the agglomeration and coarsening of the grain boundary precipitates and the size and the distance between them increased, exhibiting a discontinuous distribution, which blocked the anodic corrosion channel and hindered the corrosion progress, thus improving the corrosion resistance of the alloy.