The German government has set to achieve greenhouse neutrality by 2045. One of the main sources of CO2 emissions is the metal industry that requires high amounts of energy in the production of primary raw materials. To tackle such a challenge, the more intensive use of secondary material sources constitutes a part of the solution [1]. Such a step would reduce reliance on primary raw material, a decrease in energy expenses and overall increase in sustainability. Since the production process of primary aluminum alloys requires 20 times more energy than remelting and reusing recycled aluminum, it would be beneficial to intensify the use of recycled aluminum alloys such as production scraps [2]. As oxidation, humidity and contamination with non-desired alloying elements can have a large influence on the processability, the microstructure as well as the resulting mechanical and physical properties an extended study is required.

In this study, the excessive AlSi35 powder of a spray compacting process which is conventionally used to process high-silicon aluminum alloys is used for laser powder-bed fusion (LPBF). AlSi35 (DISPAL S220®) is a high-silicon aluminum alloy that has already shown success in additive manufacturing. With a low coefficient of thermal expansion (CTE), high stiffness, exceptional wear and tear characteristics as well as low density, this material is a solid option in a wide array of fields and industries [3, 4]. Combined with the high degree of freedom and flexibility that especially the laser powder bed fusion (LPBF) process AlSi35 promises new opportunities in terms of technological advancements can be realized. An example are injection molding tools with internal cooling channels ensuring a homogenous temperature distribution in the tool cavity as well as avoiding distortion of the final polymer part due to thermally induced residual stresses.

In this study, the suitability of recycled AlSi35, in specific excessive powder of spray compacting processes, for an efficient additive manufacturing of robust parts with desired mechanical and physical properties for demanding applications (high complexity, high thermal stability, wear resistance) are investigated. At first, a parametric study is conducted. After the definition of suitable manufacturing parameters, the additively manufactured specimens are examined by using energy dispersive X-ray spectroscopy (EDS), light microscopy and the laser flash method to determine the chemical composition of the material, the microstructure and the CTE. In addition, the thermal expansion of the material is investigated by analyzing the surface displacements during heating and cooling cycles with digital image correlation (DIC). In addition, the mechanical properties are determined by using quasi-static as well as cyclic testing methods depending on different heat treatment states. Finally, a demonstrator will be designed and manufactured using LPBF to showcase the material properties.

The poster will give an overview about the methodical procedure and will show first results about the processability of recycled AlSi35 and the resulting microstructure as well as material properties.

References

[1] Pothen, F., Growitsch, C., Engelhardt, J., and Reif, C. 2019. Schrottbonus. Externe Kosten und fairer Wettbewerb in den globalen Wertschöpfungsketten der Stahlherstellung. DOI=10.24406/publica-fhg-300126.

[2] Bundesanstalt für Geowissenschaften und Rohstoffe. B 1.2 Geologie der mineralischen Rohstoffe. Arbeitsbereich Bergbau und Nachhaltigkeit. 2020. Aluminium. Informationen zur Nachhaltigkeit. https://www.deutsche-rohstoffagentur.de/DE/Gemeinsames/Produkte/Downloads/Informationen_Nachhaltigkeit/aluminium.pdf?__blob=publicationFile&v=2.%20Zuletzt%20abgerufen%20am%2028.Januar%202023. Accessed 28 June 2024.

[3] Gränges Powder Metallurgy. 2021. Technical Data Sheet Dispal®220 AM (AlSi35). https://www.granges.com/contentassets/d56ae4a3af094e6b9dc74a509757bf1d/240606-dispal-s220-am.pdf. Accessed 28 June 2024.

[4] Risse, J. H., Trempa, M., Huber, F., Höppel, H. W., Bartels, D., Schmidt, M., Reimann, C., and Friedrich, J. 2023. Microstructure and Mechanical Properties of Hypereutectic Al-High Si Alloys up to 70 wt.% Si-Content Produced from Pre-Alloyed and Blended Powder via Laser Powder Bed Fusion. Materials (Basel, Switzerland) 16, 2.