Microstructure and mechanical properties of aluminum lattice structures fabricated via 3D printing-based investment casting

Metallic lattice structures show broad application prospects in aerospace, automotive, biomedical, and other various high-performance engineering fields due to their excellent structural characteristics such as high specific strength, stiffness, and energy absorption capacity. However, their complex geometries present significant challenges for making them with conventional casting or machining processes. To overcome such limitations, a 3D printing-based investment casting process is developed and demonstrated in this study. The process involves the fabrication of a high-precision sacrificial pattern via 3D printing, followed by making mold to cast metal, allowing for accurate reproduction of complex 3D internal structures of lattice structures. In this study, the 3D printing-based investment casting process was utilized to fabricate aluminum lattice structures. A high-resolution sacrificial pattern was designed and fabricated through a digital light processing method. After fixing the pattern within the mold, a plaster was cast and hardened to form the shell mold. Then, the sacrificial pattern was burned out, leaving a cavity for metal casting. Subsequently, molten AlSi7Mg aluminum alloy was vacuum infiltrated into the cavity using Ar gas with 1 atm pressure, followed by vacuum casting. The lattice structures were designed in a body-centered cubic forms with different lattice unit cell sizes and strut thicknesses. The effects of lattice unit cell size and strut thickness on the microstructure, local and overall mechanical properties were investigated.