夹杂物致粉末高温合金低周疲劳裂纹萌生微观机理和寿命预测

These advanced aeroengine turbine discs which are made of powder metallurgy (PM) superalloys usually suffer from non-metallic inclusions (NMIs) induced fatigue failure during the operation cycles. In order to address this problem, this project is to study the micro-mechanisms and to develop prediction tools of NMIs induced low cycle fatigue (LCF) crack initiation in PM superalloys. In this project, the NMIs will be evaluated by multi-dimensional characterization and the stress concentration effects associated with these NMIs will be quantified based on the image-based modeling. The strain distribution and evolution at the grain level around the NMIs under the cyclic loading at the typical turbine disc working temperatures will be characterized. Through these characterization and assessments, the influences of NMIs on strain localization processes can be clarified, the NMIs induced LCF crack initiation micro-mechanisms can be revealed, and the criterion used for LCF crack initiation lifetime prediction can be established. By combination of the microstructure-based crystal plasticity finite element model and the LCF crack initiation criterion, the LCF crack initiation sites and lifetime in PM superalloys can be predicted. The microstructure-sensitive mechanistic modeling framework established in this project is expected to improve the prediction accuracy of LCF crack initiation lifetime and to provide scientific supports for the improvement of life-design of PM superalloy turbine discs.

面向高性能航空发动机的发展需求，针对航空发动机粉末涡轮盘中常见的非金属夹杂物致疲劳失效问题，开展粉末高温合金非金属夹杂物致低周疲劳（LCF）裂纹萌生微观机理和萌生寿命预测研究。拟通过对粉末高温合金非金属夹杂多维度表征和应力集中效应量化评估，通过表征涡轮盘典型服役温度下夹杂物周边晶粒尺度范围内应变分布和演化，揭示疲劳载荷下夹杂物影响应变局部化进程及夹杂物致LCF裂纹萌生微观机理，建立LCF裂纹萌生准则。结合基于粉末高温合金微结构特征的晶体塑性有限元模型和LCF裂纹萌生准则，模拟预测LCF裂纹源和裂纹萌生寿命。本项目所建立的研究框架可望提高LCF裂纹萌生寿命预测精度，为提高粉末涡轮盘寿命设计水平提供科学支持。

面向高性能航空发动机的发展需求，针对航空发动机粉末涡轮盘中常见的非金属夹杂物致疲劳失效问题，开展粉末高温合金非金属夹杂物致低周疲劳（LCF）裂纹萌生微观机理和萌生寿命预测。具体包括：（1）采用多尺度、多维度微结构表征方法表征了粉末高温合金FGH4098微结构，揭示了涡轮盘典型服役温度下微结构对粉末高温合金疲劳循环变形的影响机理；（2）通过SEM-DIC表征FGH4098合金微缺口周围应变局化和演化，揭示了微结构相关的疲劳裂纹萌生机理，引入疲劳指示因子用于疲劳裂纹萌生预测；（3）建立了基于立方体素网格代表性体积单元的晶体塑性模型参数快速标定方法，标定了FGH4098合金 晶体塑性模型参数，基于FGH4098合金微结构量化表征结果，建立考虑其微结构特征的有限元模型，结合晶体塑性模型和疲劳指示因子，对FGH4098合金疲劳裂纹萌生位置和萌生寿命进行预测，取得与实验较为吻合的结果。所建立的基于粉末高温合金微结构特征和疲劳裂纹萌生微观机理的疲劳裂纹萌生预测方法可望提高疲劳裂纹萌生寿命预测精度，为提高粉末涡轮盘寿命设计水平提供技术支持。在本项目的支持下，共发表SCI学术论文5篇，申请国家发明专利5项，参加国内外学术会议5次。培养硕士研究生5人，其中毕业1人，在读4人。