Design, defect analysis, compressive strength and surface texture characterization of Laser Powder Bed Fusion processed Ti6Al4V lattice structures

Porous cellular structures of Ti alloys are becoming more attractive in aerospace, automotive and biomedical applications due to greater flexibility, lightweight, strength-to-weight ratio, and desired properties aiding osseointegration. The intricate geometries of lattices pose an extreme challenge for conventional manufacturing. Laser Powder bed fusion process offers an excellent opportunity to fabricate complex lattice structures without any design constraints. This research aims to design and LPBF printing of BCC, Diamond, Gyroid and Voronoi lattice structures. Furthermore, the influence of different lattice designs on the formation of inevitable process-induced defects and porosities, which consequently impact apparent density, compressive strength, and surface roughness is investigated. The surface roughness, defects and porosities are analysed using Alicona, optical microscopy, SEM and XCT techniques. Pycnometer and compressive testing are adopted to study apparent density and ultimate compressive strength. The results demonstrated the intertwining relationship between the multifarious lattice structures, porosities, apparent density, ultimate compressive strength and surface roughness. BCC showed the highest pores of 3764 while the Gyroid recorded the least pores of 485. Voronoi lattice displayed the highest apparent density of 99.99% whereas the BCC revealed the lowest apparent density of 98.75%. The highest UCS of 430.6 MPa for diamond lattice is credited to higher material volume, Voronoi resulted in the lowest UCS of 190.60 MPa. The intricate arbitrary design and layer-wise LPBF building of Voronoi lattice resulted in the worst surface roughness Sa of 0.59 μm while BCC's uniform surface distribution and non-existence of staircase effect led to the best Sa of 0.17 μm.