(1. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長(zhǎng)沙 410083；
2. 上海飛機(jī)設(shè)計(jì)研究院 標(biāo)準(zhǔn)材料室，上海 200232)
摘 要: 研究7449-T7951合金的高周疲勞及裂紋萌生行為。在室溫下，采用光滑及缺口試樣進(jìn)行疲勞壽命測(cè)試，應(yīng)力比(R)分別為0.5和−1.0。采用金相顯微鏡、掃描電鏡及透射電鏡對(duì)該合金的微觀組織及疲勞試樣斷口進(jìn)行分析，以揭示其疲勞裂紋萌生機(jī)理與合金微觀組織之間的關(guān)系。結(jié)果表明：7449-T7951合金具有優(yōu)異的疲勞性能；應(yīng)力比為0.5和−1.0時(shí)，光滑試樣的疲勞壽命極限(σN)分別為349和134 MPa，而缺口試樣的σN(缺口系數(shù)Kt=3.0)分別為138和70 MPa。其裂紋萌生行為受合金中粗大第二相、析出相、晶界和位錯(cuò)(滑移帶)的共同影響。
關(guān)鍵字: 7449合金；高周疲勞；疲勞裂紋；裂紋萌生
（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
