涡轮叶片用定向凝固高温合金的超高周疲劳特性和机理研究

Directionally solidified superalloys with are widely used in aero-engine turbine blades. Engine turbine blades are sometimes subjected to ultra-high cycle fatigue with high frequency and low load.The frequency can be up to ten thousand Herz, and the cycle is more than 10^7. In recent years, simulating the ultra-high cycle fatigue failure of the material by using ultrasonic fatigue testing method has become a hot issue. The ultra-high cycle fatigue behavior are mainly used for high strength steel with metallurgical defects, rare report for superalloy.In this project,we will investigate the ultra-high cycle fatigue behavior of directionally solidified superalloy. The ultra-high cycle fatigue data of superalloy at different temperatures and frequecies will be analyzed to provide fatigue parameters under real service for the material and clarify the effect of temperature and frequecy on the ultra-high cycle fatigue properties. The relationship between fatigue properties and fracture will be obtained by observation of the fracture characteristic. The evolution of the microstructure at micro-scale, including strengthening phase and dislocation structure, will be investigated and quantify the microstructure at the initial of stage of crack propagation to clarify the correlation between fatigue properties and microstructure. Actualized this project,it can provide scientific guidance and experimental basis for practical engineering applications of directionally solidified superalloy.

定向凝固高温合金被广泛应用于航空发动机涡轮叶片。在服役过程中，发动机涡轮叶片有时要遭受高频率低载荷的超高周疲劳，频率可达万赫兹，循环周次在10^7以上。人们利用超声疲劳试验方法来模拟材料的超高周疲劳失效已经成为研究热点，主要针对高强度钢等含冶金缺陷材料，但是，关于涡轮叶片用高温合金的超高周疲劳研究还处于初步阶段，本项目将在前期工作的基础上，开展涡轮叶片用定向凝固高温合金的疲劳行为研究。分析材料在不同温度和频率下的超高周疲劳性能数据，阐述温度和加载频率对材料超高疲劳性能的影响效应。观察疲劳断口失效特征，得到疲劳性能与宏微观断口特征间的关联。研究材料疲劳后的组织结构在微观尺度上的演变，包括强化相和位错结构等，定量化裂纹初始阶段的微观结构，阐明材料的疲劳性能与组织结构的关系。本项目的开展，为定向凝固高温合金在工程上的应用提供科学指导。