Identification and Modeling of Fatigue Damage Mechanisms in Al-Si-Mg Cast Alloys under Fatigue Loading at High and Very High Number of Cycles

在第二个项目阶段（pp2），将通过结合EBSD和EDX映射以及TEM检查（事后分析）在微观结构水平上进行原位拉伸，弯曲和疲劳测试，研究微观结构特征与疲劳性能之间的关系。科学发现将与成功实施的新测量方法（高分辨率热成像，交流电位下降技术，远场显微镜）以及高分辨率数字图像相关性（pp2新）的响应变量的特征曲线相关联，以了解机制与响应变量之间的相关性。响应变量与疲劳引起的微观结构变化之间的关系作为主要机制的函数将以基于模型的方式描述，并用于优化测量和测试方法。二维显微组织还将用于生成合成的、具有代表性的合金显微组织和微观组织变体，用于基于边界元的短裂纹和长裂纹扩展行为建模。基于实验和建模结果，将在数值铸造和相模拟中描述和实现微观组织与疲劳性能之间的关系。随后，将以抗疲劳材料设计为目标，研究已开发的工艺-微观结构-性能关系到复杂组件结构（底盘组件，摇臂）的可转移性。重点是在可自由选择的条件下进行凝固和热处理的Al-Si-Mg合金在高和非常高循环下的疲劳寿命的可靠预测。

Within the second project phase (pp2), the relationship between microstructural characteristics and fatigue properties will be investigated by means of combined EBSD and EDX mappings as well as TEM examinations (post-mortem) at the microstructural level by in situ tensile, bending and fatigue tests. The scientific findings will be correlated with the characteristic profiles of the response variables of the successfully implemented new measurement methods (high-resolution thermography, alternating current potential drop technique, far-field microscopy) as well as high-resolution digital image correlations (new in pp2) in order to understand the correlation between mechanisms and response variables. The relationship of the response variables with fatigue-induced changes in microstructure as a function of the dominant mechanisms will be described in a model-based manner and used to optimize the measurement and test methods. The 2D microstructures will also be used to generate synthetic, representative microstructures of the alloy and microstructure variants for boundary-element-based modeling of short and long crack propagation behavior. Based on the experimental and modeling results, the relationships between microstructure and fatigue properties will be described and implemented in numerical casting and phase simulations. Subsequently, the transferability of the developed process-microstructure-property relationships to complex component-like structures (chassis components, rocker arms) will be investigated with the goal of a fatigue-resistant material design. The focus is placed to a reliable prediction of the fatigue life at high and very high cycles for Al-Si-Mg alloys, which are solidified and heat-treated under freely selectable conditions.