Laser powder bed fusion (L-PBF) additive manufacturing has reached wide-scale technology readiness for various sectors. However, some challenges posed by the complex nature of the process persist. Limited studies investigated the correlation between the micro- and macroscopic properties of L-PBF AlSi10Mg parts and the features’ sizes with the build orientation in mind. Therefore, this study presents a comprehensive view on the “size effect” for samples larger than those available in the literature (up to 12 mm) on the defects, microstructure evolution, and mechanical properties in two build orientations using a fixed set of process parameters. Microstructural differences were observed between the build orientations, but no considerable difference with size change was detected. The porosity content was inversely proportional to the feature size irrespective of the build orientation, leading to an increase in ductility that was more evident in the horizontal specimens (~44%). This was attributed to an in-situ heat treatment. Although specimens oriented parallel to the build direction showed no significant size-effect in terms of the mechanical properties (hardness and tensile), anisotropy was evident. Based on the findings presented in the study and the scientific explanations discussed corroborated by thermal imaging during processing, it is concluded that although any set of ‘optimised’ process parameters will only be valid for a specific size range, the severity of the size-effect changes dynamically based on the range.

Most of the global production of titanium goes towards aerospace parts, where it is estimated that up to 90% of the material is lost as machining scrap due to its high resistance to deformation. Although additive manufacturing aids in reducing titanium waste through higher material utilization, waste by-products are still produced in the form of support structures, out-of-use powder, failed builds, or discarded test specimens. This work explores the potential of giving manufacturing waste in various forms a new life by recycling it into useful powder feedstock for laser powder bed fusion through a state-of-the-art ultrasonic atomisation approach. The viability of this method is assessed through investigating the feedstock’s suitability in terms of chemical composition, morphology, size distribution, flowability and packing behaviour. The printability of the recycled powder is tested and compared against standard commercially available powder to identify any discrepancies that result from the recycling process.