Spatial inhomogeneity of build defects across the build plate in laser powder bed fusion

The population of build defects as a function of position on the build plate was examined in Ti-6Al-4V specimens fabricated on two common commercial laser powder bed fusion (LPBF) systems. Using standard build parameters, X-ray computed tomography revealed that spatial heterogeneity of the defect population can be substantial, relative to the variations in defect population that can occur due to other parameters, e.g. part geometry, build orientation, and laser power schedule. To understand the potential importance of such variability, its impact on fatigue performance is considered. Asymmetries inherent to LPBF fabrication are investigated as potential sources of the spatial heterogeneity, with shielding gas flow simulations providing an explanation.