Effect of Cu/Mg Ratio on Microstructure and Corrosion Resistance of Al-Cu-Mg-Li cast Alloy During Non-Isothermal Aging

This study investigated the influence of non-isothermal aging (NIA) on microstructure, mechanical properties, and corrosion resistance of Al-Cu-Mg-Li alloy containing a Cu/Mg ratio of 1.0 and 3.8. The results show that NIA with a heating rate of 10 degrees C/min results in maximum hardness 179.3 +/- 2.3 HV and ultimate tensile strength 610.1 +/- 21.5 MPa at a temperature of 250 degrees C. Also, with increasing the Cu/Mg ratio from 1.0 to 3.8 in the alloy containing 0.75 wt% of lithium, the maximum hardness, and tensile strength increased by 35 and 45%, respectively. By increasing Cu/Mg ratio from 1.0 to 3.8 at alloy containing 0.75 wt% of lithium, T1(Al2CuLi) precipitates are formed in the microstructure instead of delta '(Al3Li) precipitates. In the Cu/Mg ratio of 3.8, due to the more potential difference between the T1 precipitates and the aluminum base, the corrosion resistance of the alloy increases 76% higher than lithium-free alloy.