Numerical and experimental investigation on flexural properties of selective laser melting (SLM) manufactured strut lattices structures from Ti-6Al-4V and Inconel 625

Abstract

Lattice structures hold a significant importance in the aerospace industry due to their ability to tailor the physical, thermal, and mechanical properties of complex components for optimal performance. This study is focused on evaluating the flexural properties of four lattice configurations - re-entrant, truncated octahedron, Kelvin, and octet cells - through static finite element analysis (FEA) and experimental three-point bending tests, as well as examining their microstructural features (as they affect the materials’ mechanical properties). High-performance alloys used for gas turbines components manufacturing, Ti-6Al-4 V and Inconel 625, were fabricated using selective laser melting (SLM) process. The necessity of this research resulted from the lack of information in the scientific literature regarding flexural properties of various additive manufactured cell types and metallic materials. The aim was to compile data that could be used to create a comprehensive database for various industrial applications. Findings from both simulations and experimental analyses indicated that the octet cell had the highest performance, with experimentally measured flexural strengths of 878 MPa for Ti-6Al-4V, respective 674 MPa for Inconel 625. Contrarily, the re-entrant cell exhibited the lowest performance, with flexural strengths of 125 MPa for Ti-6Al-4V and 116 MPa for Inconel 625. Failure in the re-entrant cells was attributed to the bending fracture of vertical rods at the connecting nodes or lattice struts, while other cell types experienced damage through a combination of bending and shear mechanisms. Dimensional deviations observed in all specimens were attributed to defects such as surface roughness, the stair-stepping effect, and internal stresses.