Effects of non-isothermal aging on mechanical properties, corrosion behavior and microstructures of Al-Cu-Mg-Si alloy

Abstract

Effects of non-isothermal aging (NIA) treatments on the mechanical properties, intergranular corrosion (IGC) and microstructures of Al-Cu-Mg-Si alloy were investigated by tensile test, intergranular corrosion test, electrochemical analysis, optical microscopy and transmission electron microscopy. Compared with isothermal peak-aging (T6) treatment, the NIA treatments effectively improve the intergranular corrosion resistance by narrowing precipitation free zones (PFZ) and breaking the continuous distribution of precipitates on the grain boundaries. Under NIA treatments, with the increase of heating rate, the width of PFZ decreases induces the improvement of intergranular corrosion resistance. The mechanical properties of NIA treatment could be enhanced by adjusting the heating rate. The tensile strength and yield strength after NIA treatment with a heating rate of 20 °C/h are increased 1.5% and 5.8% than that after T6 treatment, respectively, which is ascribed to finer intra-grain precipitates. Reasonably, the mechanical properties and intergranular corrosion resistance could be improved simultaneously by adjusting the heating rate of NIA treatments.