Effects of aging treatment on the mechanical properties and corrosion resistance of an Al-Cu-Mg-Li alloy

In this paper, the effects of as-quenched, single aging, and double aging on the mechanical properties, microstructure, corrosion resistance, and electrochemical behavior of an Al-Cu-Mg-Li alloy were investigated. Most changes only improved the mechanical properties or corrosion resistance of aluminum alloy alone, and very few of them improved the mechanical properties or corrosion resistance at the same time. The results showed that double aging treatment improved the strength, hardness, and corrosion resistance of the alloy but decreased its elongation. During the aging treatment, the corrosion morphology of the alloy gradually transformed from pitting corrosion (as-quenched) to a combination of pitting corrosion and corrosion cracks (single aging) and finally to pitting corrosion (double aging). The fracture morphology gradually changed from an uniform distribution of a mixture of large and small dimples (as-quenched) to an intergranular fracture (double aging) as aging progressed. Transmission electron microscopy results showed that the T1 phase within grains and at grain boundaries (GBs) was different between the as-quenched and double aged states. In addition, a precipitate-free zone (PFZ) formed in the double aged state. The optimal process of Al-Li alloy was determined to be pre-aging at 100 degrees C for 4 h and final aging at 160 degrees C for 24 h.