Relationship between Process Parameters and Material Properties of an Aluminium Alloy Customized for Additive Manufacturing

Kurzfassung

Additive manufacturing (AM) can be employed in a meaningful and economical manner particularly for complex and highly-integrated components that require numerous manufacturing steps or cannot even be realized with conventional production methods. One of the use-cases that has gained attention recently are heat exchangers due to the goal of using hydrogen as fuel for future civilian aircraft designs. Heat exchangers can benefit especially from the possibilities that Laser-based Powder Bed Fusion (PBF/LB or LPBF) enables, but suitable materials with high thermal conductivity as well as good mechanical and corrosion properties that simultaneously satisfy the requirement of good processability are still lacking today for different thermal cases in consideration. DLR investigates the feasibility of different heat exchanger concepts that, for instance, rely on bleed air from different stages of a hydrogen-based turbine engine. The first thermal use-case employs the heat provided by bleed air from a compression section, which in turn points to aluminium alloys as optimal choice for the heat exchangers. Therefore, the PBF/LB processing routes and materials properties of potentially suitable novel alloys such as Constellium Aheadd CP1 are being developed and optimized at DLR. Process windows aiming at very fine structure resolutions and high surface qualities as well as complementary ones for high productivity have been determined. The resulting as-built microstructures were characterized and optimized with a peak-aging heat treatment for high thermal conductivity. The formation and growth of precipitates including Al3Zr and AlxFey, e.g., at grain boundaries, was analysed. The mechanical performance and heat conductivity were assessed in the different conditions. Currently, the possibilities and limitations of printing specific structures relevant for heat exchanger design tailored to AM are being studied. The process developments will be employed in the future for the development and manufacturing of heat exchangers for hydrogen using hot air from the compressor section of turbine engine.