A holistic study of the effect of geometrical and processing conditions on the static mechanical performance of LPBF strut elements

Abstract

Laser powder bed fusion (LPBF) enables geometrical designs of great complexity, such as metamaterials. These structures are founded on elemental struts printed at various orientations and sizes. Understanding how these design variables affect mechanical properties is crucial for optimizing component performance. This work aims to systematically investigate the impact between these design variables on defects, roughness, geometrical deviations, and microstructure of Ti-6Al-4V elemental struts and correlate them with mechanical properties. The analysis shows that smaller strut diameters present an increased sensitivity to defects, reducing ductility by 45.8% on average as the diameter decreases from 1.5 mm to 0.5 mm. When compared to vertical struts, horizontally printed struts of 1.5 mm, 1 mm, and 0.5 mm present on average a respective reduction in ductility of 57.4%, 59.8%, and 70.9%, and a respective reduction in the ultimate strength of 13.3%, 24.5%, 61.2%. This has been associated with warping and increased roughness caused by dross formation. Finally, the study shows the complex interaction of process parameters' effect with the struts' orientation and size. These findings pose the basis for a more accurate and optimal mechanical design of cellular metamaterials, from the underlying material perspective.