Investigation of the laser powder bed fusion manufacturing process and quasi-static behaviour of Ti6Al4V Voronoi structures

Ti6Al4V Voronoi structures are unique lattice structures with high potential in biomedical applications, owing to their tuneable mechanical properties and superior biocompatibility. Unlike unit cell -based lattice structures, Voronoi structures have struts that are oriented in any direction relative to the build direction, which impedes process optimisation and increases the risk of internal and structural defects. Previous research has primarily focused on the mechanical properties of porous Voronoi structures with limited geometric variations. This study aims to address a broader range of geometries and relative densities, parameters that are important for orthopaedic implants. This work examines the influence of process parameters and scan strategies on both geometric accuracy and internal defects of Voronoi structures. Additionally, the deformation behaviour of an extensive geometric range of Voronoi structures is studied using uniaxial compression tests. Voronoi structures of relative density ranging from 54.6 % to 98.5 % were used in this study. The results show an improvement in geometric accuracy and a reduction in interior defects as a result of adapting the laser powder bed fusion process parameters and carefully controlling the scan strategy. In comparison to a control group of fully dense samples, the Young ' s modulus of the investigated structures ranged from 35.1 % to 97.7 %, and the compressive yield stress ranged from 32.8 % to 101.1 %. These properties exhibit positive power correlations with the relative density. Furthermore, dense Voronoi structures showed similar deformation and failure behaviour to bulk material, while porous Voronoi structures demonstrated an accumulation of local failures. Fractography analysis indicated that failures were mainly caused by local shear stress. The results of this work enhance the manufacturing process and promote applications of Voronoi lattice structures.