The mechanical properties of laser powder bed fusion (PBF-LB) parts such as fatigue strength or tensile strength are greatly influenced by the porosity occurring in the material. While it is common to achieve relative densities over 99.5% for the aluminum alloy AlSi10Mg, in practice, the formation of statistically occurring oxide pores cannot be avoided completely. Due to their irregular shape, these pores are detrimental for the mechanical properties. It is hypothesized that oxide pores can be avoided by increasing the energy input. This in turn leads to the formation of spherical keyhole pores. However, it is not sufficiently understood how keyhole porosity affects the mechanical properties with regard to oxide pores. Therefore, this work investigates the impact of keyhole pores, lack of fusion pores and oxide pores on the mechanical properties of PBF-LB AlSi10Mg parts. Results show the importance of single critical defects for the fatigue behavior compared to the impact of relative porosity and reveal the less detrimental nature of keyhole pores compared to oxide pores. Despite a much higher relative porosity, the tensile strength of specimens containing keyhole pores is comparable to that of highly dense parts whereas the fatigue strength has even improved.

As part of an international research project (HiPTSLAM), the development and holistic processing of high-performance tool steels for AM is a promising topic regarding the acceptance of the laser powder bed fusion (PBF-LB) technology for functionally optimized die, forming and cutting tools. In a previous work, the newly developed maraging tool steel FeNiCoMoVTiAl was qualified to be processed by laser powder bed fusion (PBF-LB) with a material density of more than 99.9% using a suitable parameter set. To exploit further optimization potential, the influence of dual-laser processing strategies on the material structure and the resulting mechanical properties was investigated. After an initial calibration procedure, the build data were modified so that both lasers could be aligned to the same scanning track with a defined offset. A variation of the laser-based post-heating parameters enabled specific in-situ modifications of the thermal gradients compared to standard single-laser scanning strategies, leading to corresponding property changes in the produced material structure. An increase in microhardness of up to 15% was thus obtained from 411 HV up to 471 HV. The results of the investigation can be used to derive cross-material optimization potential to produce functionally graded high-performance components on PBF-LB systems with synchronized multi-laser technology.