The commonly used Gaussian intensity distribution during the laser-based processing of metals can negatively affect melt pool stability, which might lead to defects such as porosity, hot cracking, or poor surface quality. Hot cracking is a major factor in limiting production rates of high-strength aluminium alloys in laser-based processes such as welding or the powder bed fusion of metals (PBF-LB/M). Going away from a Gaussian intensity distribution to ring-shaped profiles allows for a more even heat distribution during processing, resulting in more stable melt pools and reduced defect formations. Therefore, the aim of this study is to investigate the influence of different laser beam profiles on the processing of high-strength aluminium alloys by using a multicore fiber laser, allowing for in-house beam shaping. Single weld tracks on the aluminium alloy EN AW-5083 are produced with varying laser powers and weld speeds, as well as different beam profiles, ranging from Gaussian intensity distribution to point/ring profiles. The molten cross sections are analyzed regarding their geometry and defects, and the surface roughness of the weld tracks is measured. By using point/ring beam profiles, the processing window can be significantly increased. Hot cracking is considerably reduced for weld speeds of up to 1000 mm/s compared to the Gaussian beam profile. Furthermore, the melt pool width and depth are more stable, with varying parameters for the point/ring profiles, while the Gaussian beam tends to keyhole formation at higher beam powers. Finally, a strong decrease in surface roughness for the point/ring profiles, accompanied by a significantly reduced humping effect, starting even at lower beam powers of 200 W, can be observed. Therefore, these results show the potential of beam shaping for further applications in laser-based processing of high-strength aluminium alloys.

One major advantage of additive manufacturing is the high freedom of design, which supports the fabrication of complex structures. However, geometrical features such as combined massive volumes and cellular structures in such parts can lead to an uneven heat distribution during processing, resulting in different material properties throughout the part. In this study, we demonstrate these effects, using a complex structure consisting of three conic shapes with narrow cylinders in between hindering heat flux. We manufacture the parts via powder bed fusion of Ti6Al4V by applying a laser beam (PBF-LB/M) as well as an electron beam (PBF-EB). We investigate the impact of the different thermal regimes on the part density, microstructure and mechanical properties aided by finite element simulations as well as by thermography and X-ray computed tomography measurements. Both simulations and thermography show an increase in inter-layer temperature with increasing part radius, subsequently leading to heat accumulation along the build direction. While the geometry and thermal history have a minor influence on the relative density of the parts, the microstructure is greatly affected by the thermal history in PBF-LB/M. The acicular martensitic structure in the narrow parts is decomposed into a mix of tempered lath-like martensite and an ultrafine $\alpha$ + $\beta$ microstructure with increasing part radius. The EBM part exhibits a lamellar $\alpha$ + $\beta$ microstructure for both the cylindric and conic structures. The different microstructures directly influence the hardness of the parts. For the PBF-LB part, the hardness ranges between 400 HV${}_{0.5}$ in the narrow sections and a maximum hardness of 450 HV${}_{0.5}$ in the broader sections, while the PBF-EB part exhibits hardness values between 280 and 380 HV${}_{0.5}$.

The additive manufacturing of copper with conventional LPBF systems is challenging due to the high reflectivity of copper for wavelengths of standard infrared lasers and other characteristic properties like the high thermal conductivity. Green laser systems with a wavelength of 532nm pose an opportunity to reduce the necessary power of the laser systems and the number of defects while increasing the relative density. This study presents the results of a process development for a 532nm laser system for the LPBF process. Dimensionless indicators are used to analytically describe the probability of lack-of-fusion defects and investigate process parameters to achieve dense parts. The produced specimens are analyzed regarding their relative density as well as their hardness, tensile properties and electrical conductivity. It is found that dimensionless process indicators are generally suitable for an analytical approach in process development, but the adaptation to different processes results in the need for adjustment. A lower variation is found for the used dimensionless number compared to the volumetric energy density. The produced parts show a relative density of up to 99.5 % or more and mechanical and electrical properties, which are comparable to conventionally manufactured copper. A high relative density is achieved with a laser power of $$192 W$$ 192 W , a laser scan speed of 400 mm/s and a hatch distance of $$50 \mu m$$ 50 μ m .

The progress of additive manufacturing (AM) within the last few decades has been phenomenal, progressing from a polymeric technique to a method for manufacturing metallic aerospace components. We take a look at various technological advances which have helped paved the way for this growth, focussing on European input, as currently, 54% of AM machines are sold by European manufacturers (Wohlers, Campbell, Diegel, Kowen, Mostow, and Fidan, 2022, “Wohlers Report 2022: 3D Printing and Additive Manufacturing Global State of the Industry,” Wohlers Associates, ASTM International, Fort Collins, Colo., Washington, DC). We take deep dives into several critical topics including sensing and monitoring, preheating, and multi-laser technology and illustrate how these develop from research ideas into industrial products. Finally, an outlook is provided, highlighting the topics currently gaining research traction, and which are expected to be the next key breakthroughs.

Case-hardening steels are gaining increasing interest in the field of laser powder bed fusion (PBF-LB/M) due to their excellent weldability. In combination with post-process carburization heat treatment, the surface properties can be improved to generate high-strength products. When manufacturing larger products by means of PBF-LB/M, the in situ heat accumulation and the altered cooling rates affect the resulting material properties. Therefore, the fabrication of larger products requires an understanding on the influencing factors that affect the material properties. This work investigates the effect of different volumetric energy densities (VED) on the resulting microstructural and mechanical properties. It is found that the hardness decreases continuously along the build direction. The gradient depends on the applied energy and is stronger for higher energy inputs due to heat accumulation and lowered cooling rates. Furthermore, countering strategies are investigated to avoid process-specific hardness reduction along the build direction. This includes a reduced number of parts within the build job as well as a modified inter-layer time (ILT) between consecutive layers of the specimen. Applying a moderate inter-layer time helps to counter process-specific overheating, which is indicated by an almost homogeneous material hardness and melt pool size along the build direction.