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

选择性激光熔化（SLM）是一种增材制造工艺（AM），通过增加粉末层的应用和熔化来生产金属结构部件。这些部件的高几何复杂性导致近年来在许多工业领域进行了增材制造的研究，并测试了它们的适用性。然而，在SLM的快速发展中，出现了大量与材料相关的问题和问题，这些问题和问题是这项新技术及其生产的部件的应用和鉴定的基础。例如，对于大多数材料来说，无法保证结构部件安全使用所必需的可控和可再生孔隙率。同时，分层制造工艺也导致了定向凝固组织引起的材料力学行为的各向异性。由于这些特性和缺陷的不可避免的出现，成品零件的材料分析和质量保证及其与制造参数和零件几何形状的关系的研究还处于起步阶段。无损检测是进行综合微观结构分析和构件鉴定的重要步骤。因此，该项目的目的是基于x射线显微层析成像方法，研究微观结构和由此产生的机械性能与工艺参数和部件几何形状之间的关系，从而改善有关孔隙度减少和演变的过程控制。为此，本文将研究激光速度、激光功率和不同工程几何形状和构建方向下的舱口间距变化对SLM中广泛应用的铝合金AlSi10Mg的影响。这允许对过程-结构-属性进行评估。在这项任务的范围内，自动化的材料评估方法将主要基于x射线显微层析成像数据来开发SLM的微观结构特征。这第一次使三维可视化工艺参数和部件形状与微观结构特征和机械部件特性之间的联系成为可能。这为真正的过程控制和基于材料建模的组件行为预测开辟了道路。基于这些在样品和类部件几何形状中提取的相关性，在测试几何形状上进行了原位测试中力学性能建模的验证。

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.