The second-generation aluminum-magnesium-scandium (Al-Mg-Sc) alloy, which is often referred to as Scalmalloy®, has been developed as a high-strength aluminum alloy for selective laser melting (SLM). The high-cooling rates of melt pools during SLM establishes the thermodynamic conditions for a fine-grained crack-free aluminum structure saturated with fine precipitates of the ceramic phase Al3-Sc. The precipitation allows tensile and fatigue strength of Scalmalloy® to exceed those of AlSi10Mg by ~70%. Knowledge about properties of other additive manufacturing processes with slower cooling rates is currently not available. In this study, two batches of Scalmalloy® processed by SLM and laser metal deposition (LMD) are compared regarding microstructure-induced properties. Microstructural strengthening mechanisms behind enhanced strength and ductility are investigated by scanning electron microscopy (SEM). Fatigue damage mechanisms in low-cycle (LCF) to high-cycle fatigue (HCF) are a subject of study in a combined strategy of experimental and statistical modeling for calculation of Woehler curves in the respective regimes. Modeling efforts are supported by non-destructive defect characterization in an X-ray computed tomography (µ-CT) platform. The investigations show that Scalmalloy® specimens produced by LMD are prone to extensive porosity, contrary to SLM specimens, which is translated to ~30% lower fatigue strength.

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The additive manufacturing technique selective laser melting (SLM) is the most common process for metallic powders. The layer‐by‐layer process allows construction of components with high complex designs compared with conventional process routes. However, the orientation of parts related to the build platform and later to different loading conditions should be taken into account as the process‐induced microstructure and defects creating anisotropic mechanical behavior. To evaluate this influence of the building orientation as well as the process‐induced defects, different fatigue tests were performed on the SLM‐processed austenitic steel AISI 316 L (X2CrNiMo17‐12‐2). The distribution of the process‐induced porosity and, thus, the fatigue behavior is strongly related to the building direction, leading to a reduction of fatigue life for the tested 90° specimens of more than 90%.

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