热障涂层界面裂纹跨尺度扩展机理研究

Thermal barrier coating composites are widely used in nuclear power pressure vessels,aircraft engine, microelectronics devices and other fields with the excellent of thermal insulation properties, but their complex interface structure, poor working conditions and various failure forms make material life prediction very difficult. The project aims to study the microscopic initiation,crack propagation and macroscopic properties of the thermal barrier coating by means of experimental research, theoretical analysis and computer simulation. Crack propagation is a typical trans-scale problem, and the relationship between different scales is established by the cell unit. Firstly, the initial crack model is established according to the initiation mechanism and experimental detection in the representative volume element, and the location, distribution and size of the crack are analyzed. The influence of multi-crack coupling on the macroscopic mechanical behavior of the thermal barrier coating is studied. Secondly, the prediction model of the interface crack propagation under the thermodynamic coupling condition is established based on the trans-scale mechanics view. The extended finite element quantitative analysis of the crack propagation and spalling failure of the thermal barrier coating , revealing the variation law of the extended form and fracture parameters under the condition of thermal coupling, and realize the life prediction of multi-layer structure material. The research results have a guiding role in scientific evaluation, efficient use and the development of new materials with multi-layer structure.

热障涂层复合材料凭借其良好的隔热性能广泛应用于核电压力容器、航空发动机、微电子器件等领域，但其复杂的界面结构、恶劣的工作条件以及多样的失效形式，使得材料寿命预测非常困难。本项目拟采用实验研究、理论分析与计算机模拟相结合的方法对热障涂层的微观起裂、裂纹扩展以及宏观性能等方面进行研究。裂纹扩展是典型的跨尺度问题，通过体胞单元建立不同尺度之间的联系；首先在体胞单元中分别依据起裂机理和实验检测建立初始裂纹模型，分析裂纹位置、分布形态、尺寸大小以及多裂纹耦合对热障涂层宏观力学行为的影响规律；其次基于跨尺度力学观点建立热力耦合条件下界面裂纹扩展预测模型，对热障涂层结构裂纹的扩展及剥落失效进行扩展有限元定量分析，揭示裂纹在热力耦合条件下扩展形态及断裂参数的变化规律，实现多层结构材料寿命预测。研究结果对科学评价、高效利用以及开发多层结构新型材料具有指导作用。

热障涂层材料在高温下工作环境严苛，特别是热障涂层在服役过程中易被氧化并出现裂纹，随着氧化层增厚以及微裂纹的扩展和汇集，导致涂层过早地剥落失效，这严重限制了热障涂层的应用。本项目对热障涂层材料的力学和热学性质进行较深层次的机理分析，围绕热障涂层材料的设计、实验验证及含缺陷分析等方面展开研究。基于分子动力学系统研究了氧化锆基热障涂层的离子扩散、相变、声子运动、热输运特性等问题，发现了多种改善陶瓷高温热物理性能的途径；定量分析稀土离子在热障涂层材料中的力学和热学性质影响，确定了最佳掺杂元素及比例，得到具有良好热稳定性和强耐腐蚀性的新型热障涂层材料；建立含缺陷涂层系统微观、宏观模型，分析裂纹扩展特性，研究微观层面上微型缺陷之间相互作用机理；建立热障涂层界面裂纹多因素耦合扩展模型及单因素影响规律，得到影响裂纹扩展、连结、涂层脱落的关键因素。对于深入理解陶瓷热障涂层材料在高温下的导热机制和服役性能、探索新型高性能热障涂层材料有重要意义。