(1. 中南大学 材料科学与工程学院，长沙 410083；
2. 上海飞机设计研究院 标准材料室，上海 200232)
摘 要: 研究7449-T7951合金的高周疲劳及裂纹萌生行为。在室温下，采用光滑及缺口试样进行疲劳寿命测试，应力比(R)分别为0.5和−1.0。采用金相显微镜、扫描电镜及透射电镜对该合金的微观组织及疲劳试样断口进行分析，以揭示其疲劳裂纹萌生机理与合金微观组织之间的关系。结果表明：7449-T7951合金具有优异的疲劳性能；应力比为0.5和−1.0时，光滑试样的疲劳寿命极限(σN)分别为349和134 MPa，而缺口试样的σN(缺口系数Kt=3.0)分别为138和70 MPa。其裂纹萌生行为受合金中粗大第二相、析出相、晶界和位错(滑移带)的共同影响。
关键字: 7449合金；高周疲劳；疲劳裂纹；裂纹萌生
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Material and Standard Department, Shanghai Aircraft Design and Research Institute, Shanghai 200232, China）
Abstract:The high-cycle fatigue and crack initiation behavior of 7449-T7951 alloy were investigated. The fatigue-life tests were carried out over a range of stress amplitudes with the stress ratio (R) of 0.5 and −1.0 at room temperature for both smooth and notch specimens, respectively. Further researches were performed with the help of optical microscopy, scanning electron microscopy and transmission electron microscopy, in order to reveal the relationship between microstructure and fatigue crack initiation behavior of this alloy. The results show that 7449-T791 alloy has an excellent fatigue property. The fatigue limit (σN) of smooth specimens is 349 MPa for R=0.5 and 134 MPa for R=−1.0. While it still remains 138 MPa for R=0.5 and 70 MPa for R=−1.0 by using notch specimens with the notch factor (Kt) of 3.0. The crack initiation behavior of this alloy can be related to the result of a joint influence of inclusions, precipitations, grain structures and their interactions with dislocations or persistent slip bands.
Key words: 7449 alloy; high-cycle fatigue; fatigue crack; crack initiation
