Role of geometry on properties of additively manufactured Ti-6Al-4V structures fabricated using laser based directed energy deposition

A series of Ti-6Al-4V wall structures were additively manufactured (AM) using directed energy deposition (DED) with similar processing parameters and build paths to investigate the role of geometry on the resulting as-deposited microstructure and mechanical properties. While the aggregated tensile strengths (1049 ± 37 MPa), yield strengths (936 ± 43 MPa), and elongations (18 ± 4%) were relatively consistent, a more in-depth statistical analysis revealed statistically significant relationships between the resulting mechanical properties and the orientation with respect to the build direction. Tensile samples with the long dimension parallel to the substrate exhibited a higher average tensile strength than samples with the long dimension perpendicular to the substrate. In addition, the tensile strengths from thick multi pass wall structures were significantly higher than thin single pass wall structures. Finally, the tensile strengths decreased with increasing height above the substrate within the wall structures. Most of the observed differences in mechanical behavior can be attributed to differences observed in the average prior β grain sizes and shapes that impact the amounts of boundary strengthening within the structures. In addition, qualitative differences within the microstructure were observed at different locations within individual builds and correlated with changes in tensile strength.