Role of Cu-to-Li ratio in governing porosity, microstructure, texture, and tensile properties of cold-rolled and annealed Al-Cu-Li squeeze cast alloys

This study explores the role of the Cu-to-Li ratio on porosity, microstructure, texture, and tensile properties in two cold-rolled and annealed Al-Cu-Li squeeze-cast alloys with Cu-to-Li ratios near 2 (SC1) and 4 (SC2). In SC2, a relatively higher porosity content and a distinct pattern of porosity formation along equilibrium AlLi precipitates are notable features in both the as-cast and cold-rolled states. Annealing has a comparable effect on SC1 and SC2 alloys, resulting in the removal of most porosities. The Visco Plastic Self Consistent (VPSC) model reveals that the increased activation of slip-systems during cold rolling of SC2 results in a twofold rise in the texture intensity of the (011) [11̅1] and (110) [11̅1] components relative to SC1. In cold-rolled SC2, higher porosity, weaker texture, and more active slip systems during cold rolling contribute to reduced tensile strength as compared to SC1. The slightly lower strength and exceptional ductility (significantly exceeding the previously reported maximum of ∼35%) of the annealed SC2 alloy compared to SC1 are attributed to its decreased fraction of 2–15° low-angle grain boundaries and gradual decline in strain hardening rate, as described by the KME (Kocks, Mecking, and Estrin) model.