Cross-scale correlation between defects and fatigue strength of additively manufactured aluminum alloys samples

• Applicants: Dr.-Ing. Johanna Eisenträger; Dr.-Ing. Anastasiya Tönjes
• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 553531445

Additive manufacturing processes enable the production of components with complex geometries close to their final shape. However, the properties of additively manufactured components strongly depend on their local dimensions and cross-sectional changes, which becomes apparent both during their production and mechanical testing. For characterizing scaling effects, micro compression testing combined with appropriate transfer approaches is suitable. Previous work has shown that micro compression testing can qualify additively manufactured mini-cylinders regarding their elastic-plastic deformation behavior. A significant advantage of micro compression testing is that the samples require little material, can remain on the build plate, and the test is sensitive to changes in properties. This research project aims to develop a model for predicting the fatigue strength of additively manufactured samples based on the process parameters and micro compression test results. For the scaling approach, four sample sizes are manufactured on one building plate. In addition to the mechanical tests, the microstructure and the average defect size, the individual defect size, the length-to-width ratio and the circularity in the case of pores in the samples are analyzed metallographically and using scanning electron microscopy. Furthermore, the pore distribution is statistically evaluated. The relationship between pore distribution, scanning electron microscopy-analyzed microstructural phases, and process parameters is investigated using machine learning methods. A tailored modeling approach for predicting fatigue strength is developed in this research project. Correlations between the parameters of micro compression testing and conventional mechanical tests are identified, which is intended to be achieved through close interaction between simulations using the finite element method and experimental investigations. The alloy-independence of the model is demonstrated through evaluation on another aluminium alloy.

• DFG Programme: Research Grants
• Co-Investigator: Professorin Dr.-Ing. Brigitte Clausen