Brazing of nickel-based alloys plays a major role in the assembly of turbine components, e.g., abradable sealing systems. In a brazed joint of nickel-based alloys a composition of brittle and ductile phases can be formed if the brazing conditions are not ideal. This heterogeneous microstructure is a crucial challenge for predicting the damage behavior of a brazed joint. The initiation and evolution of microdamage inside of the brittle phase of a virtual dual-phase microstructure representing the material in a brazed joint is studied by means of numerical simulations. A phase field approach for brittle damage is employed on the microscale. The simulation approach is capable of depicting phenomena of microcracking like kinking and branching due to heterogeneous stress and strain fields on the microscale. No information regarding the initiation sites and pathways of microcracks is needed a priori. The reliability of calculating the effective critical energy quantities as a microstructure-based criterion for macroscopic damage is assessed. The effective critical strain energy density and the effective critical energy release rate are evaluated for single-phase microstructures, and the approach is transferred to dual-phase microstructures. The local critical strain energy density turns out to be better suited as a model input parameter on the microscale as well as for a microstructure-based prediction of macroscopic damage compared to a model employing the energy release rate. Regarding the uncertainty of the model prediction, using the effective critical energy release rate leads to a standard deviation which is five times larger than the standard deviation in the predicted effective critical strain energy density.

镍基合金的钎焊在涡轮机部件（例如耐磨密封系统）的组装中发挥着重要作用。在镍基合金的钎焊接头中，如果钎焊条件不理想，就会形成脆性相和延性相的组合物。这种异质微观结构是预测钎焊接头损伤行为的关键挑战。通过数值模拟研究了代表钎焊接头材料的虚拟双相微观结构的脆性相内部微损伤的引发和演变。在微观尺度上采用了脆性损伤的相场方法。该模拟方法能够描述由于微尺度上的异质应力和应变场而导致的扭结和分支等微裂纹现象。事先不需要有关微裂纹的起始位置和路径的信息。评估了计算有效临界能量作为基于微观结构的宏观损伤标准的可靠性。评估了单相微观结构的有效临界应变能密度和有效临界能量释放率，并将该方法转移到双相微观结构。与采用能量释放率的模型相比，局部临界应变能密度更适合作为微观尺度上的模型输入参数，以及基于微观结构的宏观损伤预测。关于模型预测的不确定性，使用有效临界能量释放率会导致标准偏差比预测的有效临界应变能密度的标准偏差大五倍。