Micro-macro characterization and modeling of fatigue properties of hybrid welded joint of AlSi10Mg parts produced by selective laser melting and casting

• Applicants: Professorin Dr.-Ing. Ghazal Moeini; Professor Dr.-Ing. Thomas Niendorf
• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins ; Metallurgical, Thermal and Thermomechanical Treatment of Materials
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 450156756

Innovative lightweight design requires coordination of optimized component design, adapted manufacturing processes and appropriate material selection. Selective laser melting (SLM), as a metal additive manufacturing process, provides the advantage of virtually tool-free manufacturing almost without any limitations regarding structural complexity. However, a major restriction for the widespread application of SLM as an industrial manufacturing procedure is the limited size of the products. Therefore, there is a clear need to study the weldability of additively manufactured components to conventionally manufactured components in assemblies. Particularly, friction stir welding (FSW), as a solid-state welding process, is numerously employed in order to avoid common weld solidification related problems. However, there is still lack of quantitative description of the influence of inhomogeneous microstructure and porosity on the variability of fatigue response of friction stir welded hybrid joint of additive manufactured parts, which makes it difficult to specify the safety factor for cyclic loading conditions being important for many industrial applications. Additionally, the efficient development and optimization of SLM welded joints requires simulation, where the microstructural heterogeneity of local areas of the welded parts must be taken into account.The main goal of the proposed research project is to develop a microstructure- and defect-sensitive computational scheme to predict the fatigue behavior of friction stir welded joint partners produced by SLM and casting processes, taking into account the microstructural features of all regions in the welded joint, i.e. microstructure, chemical composition, phase fractions and imperfections (i.e. porosity). Lightweight aluminum alloy AlSi10Mg samples processed by SLM and casting processes will be considered. Solid-state friction stir welding will be used to produce sound welds of hybrid components.Comprehensive mechanical and microstructural characterization will be performed on the SLM and as-cast AlSi10Mg components as well as their friction stir welded joints. The material characterization provides the necessary input for the development of a microstructure- and defect-sensitive fatigue model of the hybrid welded joint. The microstructure- and defect-sensitive fatigue simulation will be performed based on the real microstructure of local areas of the welded joint. Eventually, the effect of microstructure characteristics on the local mechanical properties, especially the fatigue behavior, of the SLM component and the hybrid welded joint will be simulated and validated with the experiments.

• DFG Programme: Research Grants