摘要：本文通过扫描电子显微镜原位观测，对三个不同的加载晶向（[010],[011]和[111]）的试样进行低周疲劳试验，研究了镍基单晶高温合金的疲劳小裂纹扩展行为。观测结果表明，裂纹沿着倾斜于加载方向的主导滑移平面{1 1 1}面扩展。同时为了考察疲劳小裂纹扩展的驱动力，本文对三维斜裂纹进行了有限元建模分析，并利用主导滑移平面上的塑性区尺寸较好地描述了疲劳小裂纹扩展行为。

　　关键词：疲劳小裂纹扩展，镍基单晶高温合金，有限元分析，塑性区尺寸，主导滑移平面

The Effect Of Crystal Orientation On Low Cycle Small Fatigue Crack Propagation In Ni-Base Crystal Superalloy

 Qiu Wenhui^*，Shi Huiji^*
*( School of Aerospace, Tsinghua University, Beijing 100084，China )

　　Abstract: Based on in-situ observations by scanning electron microscopy （SEM）， small fatigue crack propagation behaviors of a nickel-base single crystal （SC） superalloy were studied. Specimens with three different loading orientations, i.e., [0 1 0], [0 1 1] and [1 1 1], were tested in stress-controlled low cycle fatigue （LCF） tests with stress ratio R=0.1 at 550. Slip traces along {1 1 1} slip planes were observed and cracks, which were inclined to the loading direction, propagated in dominant crystallographic manners. In order to evaluate the driving forces for inclined crack propagation, three-dimensional anisotropic linear elastic finite-element （FE） analysis was conducted. It is found that the plastic zone size in the dominant slip plane can effectively characterize small crack growing behaviors.
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