Material- and process oriented non-destructive testing of additively manufactured components by computed tomography

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Selective laser melting (Abbr. SLM) is an additive manufacturing process (Abbr. AM), in which metallic structural components can be produced by the incremental application and melting of powder layers. The high geometric complexity of such components has led to the AM being investigated in many industrial fields in recent years and tested for their applicability. Within this rapid development of SLM, however, a large number of material-related questions and problems arise which are fundamental in the application and qualification of this new technology and the components produced with it. For example, a controllable and reproducible porosity, which is necessary for a safe use in structural components, cannot be guaranteed for most materials. At the same time, the anisotropy in the mechanical material behavior due to the directionally solidified microstructure is caused by the layerwise manufacturing process. Due to the inevitable occurrence of such characteristics and imperfections, the question of the material analysis and quality assurance of finished components and the correlation to the manufacturing parameters and component geometries is still at the beginning of research. Non-destructive testing represents an important step on the way to comprehensive microstructure analysis and component qualification.The aim of this project is therefore to investigate the relationships between microstructure and resulting mechanical properties to the process parameters and the component geometry based on X-ray microtomographic methods and thus to improve the process control with regard to the reduction and evolution of the porosity. For this purpose, the aluminium alloy AlSi10Mg, which is widely used in SLM, will be investigated under variation of laser speed, laser power and hatch spacing for various engineering geometries and build directions. This allows evaluation of process-structure-property. Within the scope of this task, automated, materialographic evaluation methods are to be developed mainly on the basis of X-ray microtomographic data for microstructural features in SLM. For the first time, this allows for a possible linking of the three-dimensionally visualized process parameters and the component shape with the microstructural characteristics and the mechanical component properties. This opens the way for a real process control and a prediction of the component behavior based on material modeling. On the basis of these extracted correlations in samples and component-like geometries, a validation of the modeling of mechanical properties in an in-situ test is carried out on a test geometry.