Martin Guggemos

Friction stir additive manufacturing (FSAM) is an emerging additive manufacturing process for fabricating large aerospace components made from aluminum alloys (e.g., EN AW-7075-T6). In the studies presented in this article, the hardness losses typical for this process were addressed. The objective of the investigations was to model these hardness losses using non-numerical methods, thereby increasing their applicability to industry. It was demonstrated that the hardness of the topmost layer was similar across parts with different numbers of layers due to the application of a temperature control system. A time-temperature metric (called cumulated hold time) was defined to predict the mean hardness of the underlying reheated layers (correlation coefficient of − 0.951). Using the lumped capacitance method, the cumulated hold time was modeled from the energy per length during welding. The developed submodels enable prediction of hardness profiles with an RMSE of 2.3 HV 0.2 and identification of suitable process parameters without measuring the part’s temperatures during fabrication. Experimental investigations showed that the welding temperature had a small positive effect on the hardness of the top layers and a negative one on the bottom layers; however, the positive effect of the welding speed on the hardness of all layers was dominant.

Compound casting is a process in which a single component is made from two metallic materials, such as aluminum and steel. Solid-liquid bimetallic compounds can be produced by suitable process control. This technology can reduce the number of joining processes, and the specific properties of the respective metal component can be used for specifically designed product properties, for example, where lightweight and high strength are needed. This paper presents an experimental methodology for producing a purely material-bonded bimetallic joint from cast aluminum and zinc-coated sheet steel in 3D sand casting using an inductive heating system. The process-related temperature characterisation in the compound zone is described using a heating test rig and temperature measurements. It shows that inductive preheating can only produce a material bond between the aluminum casting and the coated steel sheet. Shear tensile tests showed strengths between 15 MPa and 22 MPa. Laser surface pre-treatment using laser ablation cutting on the coated steel sheet was carried out to investigate the benefit of possible microform-locking. The results show a strength-reducing influence on the tensile shear tests. Micrographs showed the formation of Al_4.5FeSi and Al₇Fe₂Si, as well as the formation of other undefined intermetallic phases. The thickness of the compound zone is 10 µm.