Manufacturing size effect on the structural and mechanical properties of additively manufactured Ti-6Al-4V microbeams

Functionality and Mechanical Performance of Miniaturized Non-Assembly Pin-Joints Fabricated in Ti6Al4V by Laser Powder Bed Fusion

“…This weakening explains the relative strong loading drop from 0 to 10 µm joint clearance and the observed underperformance for specific joint clearances, where it is likely that the resulting porous structure initiated an early crack in the pin. These load capacity changes fell a bit short for pin-joint B, which can be explained by the size effect observed by Yin et al [26]. This tensile strength investigation also shows an upper limit for the joint clearance.…”

“…This correlation is backed by the observation of adhering powder particles on LPBF surfaces [17,25], especially at overhanging surfaces. Furthermore, specimens with exactly the same fabrication as the pin-joints show adhering powder particles in scanning electron microscopy and computer tomography images [20,26]. Therefore, an adhering powder particle can potentially bridge the gap of the joint clearance of 10 to 60 µm leading to local fusion.…”

“…The maximal force was reduced by more than half compared to the rigid joint, and the travel distance quartered its value. This can be explained by the manufacturing size effect; the correlation of pore volume to surface-to-volume ratio of microbeams, described by Yin et al [26]; and the mechanical change of a tensile test of a single body to that of a multibody system, introducing friction, abrasion and potential transverse forces due to rough surfaces interacting. Thereby, the rough surface can lead to the multibody interlocking at a slight angle to the pin's axis, introducing potential transverse forces.…”

Influence of Mean Stress and Building Orientation on the Fatigue Properties of Sub-Unital Thin-Strut Miniaturized Ti6al4v Specimens Additively Manufactured Via Laser-Powder Bed Fusion

“…defects with a larger size than the previously reported data. This might be ascribable to a greater number of defects of larger size in proximity of the outermost surface rather than in the central part of the strut [30].…”

“…These factors contribute to the relatively poor fatigue life of additively manufactured Ti6Al4V components compared to the wrought material. Additionally, the high surface-tovolume ratio associated with small specimen size and the specimen building orientation are fundamental factors affecting defect sensitivity and distribution at the local scale [30]. The role of the building orientation is strongly related to the different heat transfer characteristics occurring during the solidification process of the powder.…”