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

创新的轻量化设计需要优化的组件设计，适应的制造工艺和适当的材料选择的协调。选择性激光熔化（SLM）作为一种金属增材制造工艺，提供了几乎无工具制造的优势，几乎没有任何结构复杂性的限制。然而，SLM作为工业制造程序广泛应用的一个主要限制是产品的有限尺寸。因此，很有必要研究增材制造部件与常规制造部件在装配中的可焊性。特别是搅拌摩擦焊，作为一种固态焊接工艺，为了避免常见的焊接凝固问题，被大量采用。然而，对于非均匀组织和孔隙率对增材制造零件搅拌摩擦混合接头疲劳响应变异性的影响，目前还缺乏定量描述，这使得循环加载条件下的安全系数难以确定，而循环加载条件对许多工业应用至关重要。此外，SLM焊接接头的高效开发和优化需要仿真，其中必须考虑焊接件局部区域的微观组织不均匀性。提出的研究项目的主要目标是开发一种微观结构和缺陷敏感的计算方案，以预测由SLM和铸造工艺生产的搅拌摩擦焊接接头的疲劳行为，同时考虑焊接接头中所有区域的微观组织特征，即微观结构、化学成分、相分数和缺陷（即孔隙率）。将考虑采用SLM和铸造工艺加工的轻质铝合金AlSi10Mg样品。固体搅拌摩擦焊将用于生产混合动力部件的焊接。将对SLM和铸态AlSi10Mg部件及其搅拌摩擦焊接接头进行全面的力学和显微组织表征。材料特性为建立混合焊接接头的微观结构和缺陷敏感疲劳模型提供了必要的输入。基于焊接接头局部真实组织进行微观组织和缺陷敏感疲劳模拟。最后，通过实验模拟验证了微观组织特征对SLM构件和混合焊接接头局部力学性能尤其是疲劳性能的影响。

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.