Mechanical Property and Intergranular Corrosion Sensitivity of Zn-Free and Zn-Microalloyed Al-2.7Cu-1.7Li-0.3Mg Alloys

The influence of 0.72 pct Zn addition on the tensile properties of Al-2.7Cu-1.7Li-0.3Mg alloys was investigated. Their intergranular corrosion (IGC) dependence on aging [T6 type at 423 K (150 °C) and 448 K (175 °C) and T8 type at 423 K (150 °C)] time was studied. An IGC diagram associated with aging process was established. The addition of 0.72 pct Zn enhanced the strength of the Al-Li alloy with T6 type aging at 448 K (175 °C). With aging process, the corrosion mode of the T6-aged Al-Li alloys was changed in the following order: pitting and local IGC (initial aging stage), general IGC (underaging stage), local IGC (near peak-aging stage), and pitting (overaging stage) again. The IGC depth was increased first and then decreased with aging time extension. The corrosion potential change of grains and the microstructure variation were used to explain the IGC sensitivity of the Al-Li alloy with different tempers. Meanwhile, 0.72 pct Zn addition decreased the IGC sensitivity of the Al-Li alloy, especially the T6-aged Al-Li alloy.