Effect of Cu/Li Ratio on Porosity and Microstructural Evolution of Gravity and Squeeze-Cast Al-Cu-Li Alloys

The present study investigates the effect of the Cu/Li ratio on the porosity and microstructural evolution of two Al-Cu-Li alloys manufactured through gravity and squeeze-cast routes. The alloy with Cu/Li similar to 4 exhibits a unique compositional segregation pattern and a higher degree of preferred crystallographic orientation than the alloy with Cu/Li similar to 2, regardless of the manufacturing method (gravity or squeeze cast). A specific segregation pattern in alloy with Cu/Li similar to 4 occurs due to the preferential precipitation of Cu-rich Al2Cu and Al2CuLi precipitates and strong texture along the component {113}< 581 >. Homogenization of gravity and squeeze-cast alloys reduces segregation, but the alloys produced through the squeeze-cast route have more capability to reduce segregation. The alloy with a Cu/Li ratio similar to 4 displays less response to the post-cast homogenization treatment than the alloy with a Cu/Li ratio similar to 2. The X-ray micro-computed tomography study reveals that the Cu/Li ratio greatly influences the internal and surface porosities, and it is higher for the gravity-cast alloy with Cu/Li similar to 2 than Cu/Li similar to 4. Squeeze casting helps to eliminate most of the porosities in alloys with a Cu/Li similar to 2 but leaves a considerable number of porosities in alloys with a Cu/Li similar to 4.