Microstructural characterization and thermomechanical behavior of additively manufactured AlSi10Mg sheet cellular materials

There has been an increasing interest in designing new types of architected metallic cellular structures (metallic meta-structures) for various engineering applications, such as thermal management devices, due to the advancements in metallic additive manufacturing technologies. In this work, the microstructure and mechanical properties of as-built and heat-treated additively manufactured AlSi10Mg triply periodic minimal surface (TPMS) sheet-based Schoen's I-graph - Wrapped Package (IWP) cellular structures are studied. Tensile coupons of the base material and IWP cellular structures are fabricated using laser powder bed fusion 3D printing technique, and thermomechanical tests are carried out. Scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), micro-computed tomography (micro-CT), and optical microscopy were utilized to visualize the surface morphology, fracture surfaces of the tensile coupons, grain orientation maps, and internal morphology of the samples. Micro-CT and experimentally measured relative densities of the fabricated cellular structures were found to be less than designed mainly due to the lack of proper fusion of metallic powder on complex surfaces leading to voids, especially at low relative densities. As-built samples undergo compression tests at 25 °C and exhibited brittle fracture while heat-treated samples undergo compression tests at 25 °C and 150 °C and exhibit more ductile behavior which is attributed to the grain growth during heat treatment, which was determined through the study of the EBSD maps. The tensile strength of the base material decreases with the increase of testing temperature, which is associated with a significant increase in elongation at fracture.