07 Fakultät Konstruktions-, Produktions- und Fahrzeugtechnik

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/8

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Institute: search.filters.UBSInstitut.Institut für StrahlwerkzeugeSubject: search.filters.subject.670Author: search.filters.author.Schulze, Volker

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    Local laser heat treatment of AlSi10Mg as-built parts produced by Laser Powder Bed Fusion
    (2024) Kramer, Steffen; Jarwitz, Michael; Schulze, Volker; Zanger, Frederik
    Today, complex structural components for lightweight applications are frequently manufactured by laser powder bed fusion (PBF-LB), often using aluminum alloys such as AlSi10Mg. However, the application of cyclic load cases can be challenging as PBF-LB produced AlSi10Mg parts typically have low ductility and corresponding brittle failure behavior in the as-built condition. Therefore, this paper presents investigations on the feasibility of a laser heat treatment of PBF-LB produced AlSi10Mg parts to locally increase the ductility and decrease the hardness in critical areas. Potential heat treatment process parameters were derived theoretically based on the temperature fields in the material calculated assuming three-dimensional heat conduction and a moving heat source. PBF-LB produced specimens were then laser heat treated at varying laser power and scan speed. Hardness measurements on metallographic cross sections showed hardness reductions of over 35 % without inducing hydrogen pore growth.
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    Comparison of in-process laser drying with furnace and vacuum drying to reduce moisture of AlSi10Mg powder processed in Laser Powder Bed Fusion
    (2024) Lubkowitz, Victor; Fayner, Leonie; Kramer, Steffen; Schulze, Volker; Zanger, Frederik
    In most powder bed-based laser melting systems (PBF-LB), metal powders must be handled without inertization but in an air atmosphere for a short time, increasing the AlSi10Mg powder moisture and reducing the achievable component density. Consequently, different drying methods were investigated. Drying in a furnace with an inert atmosphere, using a vacuum to evaporate the water at low temperatures, and vaporizing moisture layerwise from the spreaded powder with a defocused, low-power laser beam as a further process step of the PBF-LB process. Therefore, four different moisturized powders, which were dried with different settings for the drying methods, are analyzed. All drying methods reduce the moisture content of the powder, with in-process drying being the most effective. Due to the oxide layer growth around the particles during furnace and vacuum drying, the achievable sample density after drying is worse. In-process drying with low energy density is the best option to reach a reduction of hydrogen pores and an increase of density.
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    Investigation of the formation and reduction of hydrogen porosity during laser welding of additively manufactured AlSi10Mg parts
    (2026) Kramer, Steffen; Lubkowitz, Victor; Haas, Michael; Michel, Johannes; Spurk, Christoph; Olowinsky, Alexander; Faria, Guilherme Abreu; Jarwitz, Michael; Graf, Thomas; Schulze, Volker; Zanger, Frederik
    With the increasing industrial implementation of additively manufactured metal parts, the welding of such components gains importance. Due to size limitations of laser powder-bed fusion (PBF-LB) machines and design constraints, subsequent joining processes are required. However, the weld seam quality of PBF-LB manufactured parts, particularly aluminum parts, is still limited by pore formation in the weld seam. These pores are believed to be primarily caused by the agglomeration of hydrogen. Therefore, this study investigates the pore formation during laser beam welding of PBF-LB manufactured AlSi10Mg parts by means of in-situ high-speed synchrotron X-ray imaging. In addition, an in-situ laser powder drying process is investigated to reduce the hydrogen content of PBF-LB manufactured aluminum parts in order to prevent the formation of hydrogen porosity during the subsequent welding process. Results show that pores predominantly form in the interdendritic region at the solidification front due to the locally increased hydrogen concentration. By applying laser powder drying, the hydrogen content can be reduced by up to 25%, thereby effectively preventing the formation of hydrogen pores.