A closer look at the role of Zn in the microstructure and corrosion of an Al-Cu-Li alloy

The influence of various amounts of Zn addition on the microstructure and associated intergranular corrosion of Al-2.8Cu-1.7Li-0.4Mg-0.3Mn-0.12Zr alloys was studied using transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy, and corrosion and electrochemical techniques. The added Zn was incorporated into the precipitates at the grain boundaries (GBs). Three types of phases at the GBs were confirmed. The quantity and space of the coarse phases at the GBs were related to Zn addition. The Zn addition decreased the potential difference between the conversed coarse phase (containing Zn) and the adjacent matrix, which improved the intergranular corrosion resistance.