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（pp 2），显微组织特征和疲劳性能之间的关系将通过结合EBSD和EDX映射，以及TEM检查（事后）在显微组织水平的原位拉伸，弯曲和疲劳试验进行研究。科学发现将与成功实施的新测量方法（高分辨率热成像、交流电位降技术、远场显微镜）的响应变量特征曲线以及高分辨率数字图像相关性（pp 2中的新内容）相关联，以了解机制与响应变量之间的相关性。将以基于模型的方式描述响应变量与疲劳引起的微观结构变化的关系，并用于优化测量和测试方法。2D微观结构还将用于生成合金的合成的、代表性的微观结构和微观结构变体，用于短裂纹和长裂纹扩展行为的基于边界元的建模。基于实验和建模结果，微观结构和疲劳性能之间的关系将被描述和实施的数值铸造和相模拟。随后，开发的工艺-微观结构-性能关系的可转移性，以复杂的组件结构（底盘组件，摇臂）将进行调查的耐疲劳材料设计的目标。重点放在可靠的预测疲劳寿命在高和非常高的循环Al-Si-Mg合金，这是固化和热处理在自由选择的条件下。

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.