Deformation mechanisms and fatigue crack initiation in single crystal nickel superalloys

尽管燃气涡轮发动机中镍高温合金部件的设计具有较高的安全系数，但最终仍会出现部件失效和材料退化。疲劳失效仍然是这些部件失效的最常见原因，并以机械、热机械和蠕变的形式存在；循环应力和应变导致高应力集中区域、复杂几何形状、孔隙和夹杂物周围的局部塑性变形，从而导致疲劳裂纹的产生。对这一过程的更充分的了解将导致更准确的组件寿命预测，从而实现更安全的操作并降低成本。对缺口单晶镍试样在疲劳载荷下进行了疲劳寿命测试；利用材料数据，以及晶体塑性有限元（CPFE）建模，已经生成了复杂的模型来根据损伤准则估计疲劳寿命。利用代表性体积元（RVE）建立了这些合金微观结构的详细模型，以便提取γ / γ′微观结构中不同滑移系统的滑移强度，从而创建了两相代表性模型。这些模型将用于模拟缺口单晶试样的疲劳载荷，以确定疲劳裂纹萌生的机制驱动因素。

Despite high safety factors in the design of nickel superalloy components in gas turbine engines, part failure and material degradation still ultimately occur. Fatigue failure remains the most common cause of failure for these components, and exists in the forms of mechanical, thermomechanical and creep; cyclic stress and strain leads to localised plastic deformation at regions of high stress concentration, around complex geometries, pores, and inclusions, which results in the initiation of fatigue cracks. A greater understating of this process will lead to more accurate component lifing predictions, enabling safer operation and a reduction in cost.Notched single crystal nickel samples have been tested under fatigue loading to determine fatigue life; using material data, along with crystal plasticity finite element (CPFE) modelling, complex models have been generated to estimate fatigue lives using damage criteria. Detailed models of the microstructure of these alloys have been created using representative volume elements (RVE) in order to extract slip strengths of different slip systems present in the gamma/gamma' microstructure, creating a two-phase representative model. These models will be used to simulate fatigue loading of notched single crystal samples to determine any for mechanistic drivers for fatigue crack initiation.