Cellular metals provide attractive properties, making them suitable for the use in various industrial sectors such as lightweight design, biomedical engineering or chemical engineering. Due to their highly porous and lightweight structure, in combination with their base material, advanced mechanical and chemical properties are enabled. In this field, cellular metals with triply periodic minimal surface (TPMS) lattice structures have emerged within the last decade. Their highly periodic three-dimensional structure leads to a material class with high adaptability in terms of desired properties. The technological progress of additive manufacturing of metallic and polymeric structures was crucial to enable the production of TPMS foams. The increased reproducibility and precision of the processes made it possible to produce fine structures in 3D printing for the first time. As a result, open-cell TPMS foam structures can be printed directly from metallic materials using SLM for example, or can be produced by using them as lost polymer templates in casting. Since cast materials can exhibit higher strength or ductility than printed metallic materials, we investigated and characterized the use of different Al- and steel-based TPMS structures, produced by investment casting, within this work.

MSLattice freeware is used for the generation of Diamond, Gyroid and IWP (solid and sheet, each) structures with relative densities ρrel of 0.1 up to 0.4. The models were 3-D-printed using SLA technique. The subsequent investment casting of the polymer templates is performed using centrifugal casting with commercial pure EN AC 42100 (AlSi7Mg) and AISI 420 (X40Cr12). For the evaluation of the mechanical properties, the foams are being examined under quasi-static compressive loading up to densification. This provides an overview of the mechanical performance of cast TPMS structures, which can also be considered as an alternative for other open-cell metal foams used in lightweight design.

Jan Frömert