Abstract In this study, the influence of various process parameters on the porosity of Ti-6Al-4V parts fabricated via Powder Bed Fusion – Laser Based (PBF-LB) is investigated. Three different layer thicknesses (30 μm, 60 μm, and 120 μm) were analyzed to define process windows enabling a build-rate acceleration while keeping the porosity below 0.1%. Through iterative parameter refinement, the effects of laser power, scan speed and hatch distance were examined in terms of linear energy density (LED), energy transmission density (ETD) and volumetric energy density (VED), and their influence on the formation of process-related defects such as pores. Correlations between these energy metrics and pore formation types (keyhole vs. lack-of-fusion) are discussed. The results demonstrate that process acceleration by a factor of more than 3 is possible while maintaining high quality of the components in terms of internal porosity. In addition, an accelerated method for manufacturing components using the PBF-LB process is presented, in which components are manufactured at very high build-rates but with increased porosity and then brought to the target porosity of 0.1% using the HIP process. This has made it possible to accelerate the build-rate in PBF-LB production by a further 32%. Accounting for the additional time required for HIP, the HIP route is faster than using the accelerated, which achieves the target porosity in as-built condition, for parts larger than 1421 cm 3 .

Abstract Laser directed energy deposition (LDED) is widely used in manufacturing but defects such as lack of fusion, porosity, and inhomogeneous microstructures are reducing the mechanical strength. To solve these issues, ultrasonic vibration-assisted (UV-A) LDED has been introduced. Studies show that ultrasonic vibration enhances the strength of the fabricated workpiece by reducing these defects. To control the mechanical properties and defect formation in LDED, it is essential to analyze the material flow inside the fabricated part. Despite many advances, understanding the material trajectories inside the fabricated part is still insufficient. This research aimed to investigate the material movement along the vertical and across the horizontal deposition direction. Experiments were designed utilizing an ultrasonic vibrator to examine the effects of ultrasonic vibration on material movement. Fe–Cr stainless steel powder was used for fabrication with an alternative powder (pure cobalt, Co) to trace the elemental movement during the process. The result demonstrated that utilizing ultrasonic vibration resulted in a homogenous distribution of Co in the vertical direction, exhibiting around 40% more concentration in the molten pool and around 54% higher in the upper layer. UV-A LDED affected Co distribution across adjacent tracks rising from around 1.1% at Location 1 to approximately 1.3–1.6% at Locations 2–4, in contrast to the inconsistent presence of 1.1–1.7% observed solely at Locations 2 and 3 without UV-A. Lastly, the influence of material distribution due to ultrasonic vibration on microhardness of the deposited tracks was also tested and it demonstrated positive enhancement in both vertical and horizontal direction.

Recently there has been great interest in modifying commercial titanium alloys with additives to overcome certain limitations encountered during additive manufacturing. These near-net shape products usually require machining to ensure that precise tolerances are achieved but the impact of alloy modification to machinability has not yet been thoroughly explored. In this work the influence of tantalum modification of Ti–6Al–4V on the microstructure, properties and machinability of parts produced by Laser Powder Bed Fusion is explored. In particular, prior-β grain size of Ti–6Al–4V was reduced by nearly 50% upon the addition of 10 wt% tantalum. A comparative study was conducted on the machinability of Ti–6Al–4V and Ti–6Al–4V+Ta under slot milling conditions, using the supplier-recommended machining speed of 56 m/min for titanium alloys. This work demonstrates that adding tantalum refines the microstructure, reduces the overall texture by nearly 6 times, and decreases required machining energy by approximately 0.4 J/mm3 compared to Ti–6Al–4V. However, this improvement comes at the cost of accelerated tool wear, resulting in a 30% reduction in tool diameter after machining the same volume of material. This research lays the groundwork for enhancing properties and facilitating easier machining of additively manufactured titanium components.