One approach is to tailor the solidification microstructures of lightweight components using dense materials. This study examines the microstructures and mechanical properties of near eutectic Al-Cu alloys under different thermal histories, covering both high and low solidification rates found in various additive manufacturing techniques. Slow cooled lattice structures of diamond type unit cell were produced at a relatively low cooling rate by a hybrid investment casting process involving 3D printing of the lattice patterns, and rapid solidified powders of various sizes were generated by Impulse Atomization. Microstructural analysis revealed different eutectic morphologies and spacing depending on the cooling rate and location. The alloys strength was increased by spheroidization of their eutectic phases. The alloys eutectic structures were spheroidized using two spheroidization mechanisms, including (i) Thermo-mechanically by plastic deformation of as solidified samples, followed by heat treatment, and (ii) Chemically by addition of Mg and Si to the near eutectic Al-Cu alloy. Both the thermo-mechanical and the chemical spheroidization mechanism are found to improve the mechanical properties of the alloys. This study demonstrates a potential cost-effective use of heavy alloys in high-performance applications through additive manufacturing (e.g. using lattice structures) by optimizing microstructures and enhancing mechanical properties.