In Situ Investigation of Tensile Response for Inconel 718 Micro-Architected Materials Fabricated by Selective Laser Melting

Topology optimization enables the design of advanced architected materials with tailored mechanical properties and optimal material distribution. This method can result in the production of parts with uniform mechanical properties, reducing anisotropy effects and addressing a critical challenge in metal additive manufacturing (AM). The current study aims to examine the micro-tensile response of Inconel 718 architected materials utilizing the Selective Laser Melting Technique. In this context, three novel architected materials, i.e., Octet, Schwarz Diamond (SD), and hybrid Schwarz Diamond and Face Centered Cubic (FCC), were tested in three different relative densities. The specimens were then subjected to uniaxial quasi-static tensile tests to determine their key mechanical properties, including elastic modulus, yield strength, and ultimate tensile strength (UTS), as well as the scaling laws describing the tensile response of each architected material. In situ Scanning Electron Microscopy (SEM) has been performed to observe the structure and grain morphology of the 3D printed specimens along with the phase transitions (elastic, plastic), the crack propagation, and the overall failure mechanisms. The results highlight the effect of the lattice type and the relative density on the mechanical properties of architected materials. Topologically optimized structures presented a 70-80% reduction in overall strength, while the SD and SD&FCC structures presented higher stretching dominated behavior, which was also verified by the <i>n</i>-value range (1-2) extracted from the identification of the scaling laws.