Deformation mechanisms and fatigue crack initiation in single crystal nickel superalloys

尽管在燃气涡轮机发动机中镍超合金部件的设计中具有高安全系数，但最终仍会发生部件失效和材料退化。疲劳失效仍然是这些部件最常见的失效原因，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萌生。更好地理解这一过程将导致更准确的部件寿命预测，使操作更安全，降低cost.Notched单晶镍样品进行了疲劳载荷下测试，以确定疲劳寿命，使用材料数据，沿着晶体塑性有限元（CPFE）建模，复杂的模型已被生成，以估计疲劳寿命使用损伤准则。这些合金的微观结构的详细模型已经创建使用代表性体积元素（RVE），以提取存在于γ/γ '微观结构中的不同滑移系统的滑移强度，创建两相代表性模型。这些模型将用于模拟缺口单晶样品的疲劳载荷，以确定疲劳裂纹萌生的任何机械驱动因素。

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.