粉末高温合金氧致损伤促进疲劳裂纹扩展微观机理及数值模拟研究

The aim of this project is to study the micro-mechanisms of enhanced fatigue crack propagation (FCP) caused by oxygen-induced-damage (OID) in powder metallurgy (PM) Ni-based superalloys for high thrust-to-weight ratio aeroengine turbine disc application and to develop the microstructure-sensitive and mechanism-based FCP prediction tools. Following issues will be focused in this project: (1) separating the contribution of creep and OID to FCP and quantifying the influence of OID on FCP via synergistically controlling the microstructures of the PM superalloy and test variables; (2) establishing a full filed strain measurement method at the crack tip within the bulk materials and characterizing the strain distribution at the grain level at the crack tip through the established correlation of measured strain using multiple and multi-scale strain measurement techniques; (3) clarifying the microstructures-plastic deformation-element diffusion-FCP rate dependent OID micro-mechanisms at the crack tip via the characterization and analysis of stress/strain assisted oxygen diffusion and OID at the crack tip; and (4) establishing a crystal plasticity finite element model on the basis of the microstructures at the crack tip and the FCP micro-mechanisms in PM superalloys under the coupling damage of fatigue and OID, which will be used to simulate and predict OID enhanced FCP behavior. In this interdisciplinary program, the materials, mechanical and chemical analyses will be included. Through the accomplishment of this project, it is expected to establish the FCP prediction methods and tools under the fatigue and OID coupling damage in PM superalloys, which can provide strong supports to damage tolerance fatigue life design of the key hot section components in the high thrust-to-weight ratio aeroengines with increasing operation temperatures.

面向高推重比航空发动机关键件损伤容限设计需求，针对发动机涡轮盘粉末高温合金中氧致损伤促进疲劳裂纹扩展微观机理及裂纹扩展预测难题开展研究。主要包括：（1）通过协同控制粉末高温合金微结构和试验参数，分离蠕变、氧致损伤对疲劳裂纹扩展的贡献，揭示氧致损伤对疲劳裂纹扩展的影响规律；（2）通过多尺度应变测量方法所测应变的映射关联，建立合金内部裂尖全场应变测量方法，量化裂尖疲劳损伤；（3）通过对裂尖应力/应变协助氧元素扩散和氧致损伤的表征，澄清裂尖微结构-塑性变形-元素扩散-裂纹扩展速率相关的氧致损伤微观机理；（4）建立基于裂尖微结构和疲劳-氧致损伤耦合作用机理的晶体塑性有限元模型，模拟、预测粉末高温合金氧致损伤促进疲劳裂纹扩展行为。本项目体现了材料学、力学和化学多学科领域的交叉，可望建立疲劳-氧致损伤耦合作用下疲劳裂纹扩展预测方法，为高推重比航空发动机关键热端部件疲劳寿命损伤容限设计提供科学支持。

面向高性能航空发动机的发展需求，针对涡轮盘用粉末高温合金氧致损伤促进疲劳裂纹扩展微观机理及疲劳裂纹扩展速率预测开展研究。具体包括：（1）通过在真空、空气环境下的疲劳裂纹扩展试验，揭示氧致损伤影响粉末高温合金疲劳裂纹扩展的影响规律；（2）通过对裂尖氧化物和变形量化表征，揭示裂尖微结构-塑性变形-元素扩散-裂纹扩展速率相关的氧致损伤微观机理；（3）建立高温合金氧化-疲劳裂纹扩展模型，对疲劳裂纹扩展速率进行预测；（4）建立了基于微结构和晶体塑性模型的疲劳寿命预测方法，预测结果在试验结果的1.5倍分散带内。所建立的基于合金微结构和疲劳失效机理的裂纹扩展速率及疲劳寿命预测方法，可为航空发动机关键热端部件损伤容限设计提供技术支持。在本项目的支持下，发表学术论文11篇，申请国家发明专利5项；参加国内外学术会议7次，其中做邀请报告3次；培养研究生7人，其中毕业3人，在读4人。