# Compressive Behavior of Inconel 625 and Ti-6 Al-4V Strut Lattices Fabricated by LPBF
###### Abstract  
The present study assessed the compression performance of four strut lattices manufactured via laser powder bed fusion (LPBF), namely selective laser melting (SLM) from Inconel 625 and Ti-6 Al-4V. Static finite element analysis and mechanical testing were performed, and it was concluded that the experimentally determined performance trend was in good agreement with that obtained by numerical methods. The cell type greatly influences the compressive performance of the lattices, regardless of the material used for manufacturing. The best compressive performances were recorded for the octet lattice, followed by the truncated octahedron, Kelvin, and re-entrant lattices. Regarding material performance, for the first maximum compressive strength, similar results were recorded for both materials; a difference was recorded in the case of yield strength, with higher values were recorded for Ti-6 Al-4V compared to Inconel 625. The average first maximum compressive strength for the Ti-6 Al-4V lattice was between 30.39 and 290.17 MPa, and it was within a range of 16.22-258.71 MPa for Inconel 625. The elastic modulus was between 1.74 and 4.72 GPa for Ti-6 Al-4V, and 1.13 and 4.46 GPa for Inconel 625. A more ductile behavior was registered for the nickel-based superalloy than for the titanium alloy; the Inconel 625 specimens were characterized by a bending-dominant damage mode, and Ti-6 Al-4V specimens were characterized more by a stretch-dominant damage mode. lattice; cells; metamaterials; Inconel 625; Ti-6 Al-4V; compression; SLM +
Footnote †: journal: Applied sciences  
of cellular solids. They differ from the stochastic category (foams) because they are an architecture array of spatial periodic unit cells [9]. Lattice structures can be manufactured using conventional manufacturing processes, such as direct foaming, investment casting, wire weaving, powder metallurgy, and snap-fitting [10; 11; 12; 13; 14; 15]. However, these methods have major drawbacks, like the lack of precise control over pore size and wall thickness and inconsistent performance, making them unreliable for real applications. In addition, they often need additional steps like assembly or bonding, which complicates and slows the manufacturing process, making it difficult to manufacture a wider variety of structures. The development of lattice metamaterials by AM is considered a significant leap forward in engineering, design, and manufacturing capabilities as AM is a more user-friendly, time-efficient, and flexible method to create such structures with precise geometries than conventional manufacturing technologies. Integrating lattice structures into modern applications promises to push the boundaries of material science and engineering, enabling the development of advanced materials and structures. Their unique characteristics (e.g., high strength-to-weight ratio, high mechanical properties, good acoustic and thermal performances, and the ability to absorb energy efficiently) make them desirable for multiple industries, including biomedical, aerospace, automotive, robotics, and architecture [10]. Several software packages have been developed and can be applied for lattice structure design and topology optimization (Altair OptiStruct/Inspire, nTop--former nTopology, AutodesFusion 360 with Netfabb, Ansys Discovery, Siemens NX/Solid Edge, Dassault Systems Solidworks, Creo, Materialize/3-Matic STL, Synopsys/Simpleware ScanIP [11; 12]). Over the years, many categories of periodic lattice structures have been developed: strut lattices, surface-based lattices (which include triply periodic minimal sur-faces--TPMSs), and planar-based lattices. Figure 1 presents many examples of lattice structures with multiple unit cells (images generated in nTop software, version 4.9--nTopology Inc., New York, NY, USA, designed with a 2 mm length cell distributed over a cube with a 10 \(\times\) 10 \(\times\) 10 mm\({}^{3}\) volume). Many self-standing studies and reviews on additive-manufactured lattice structures are available in the scientific literature.