摘要：本文通過掃描電子顯微鏡原位觀測，對三個不同的加載晶向（[010],[011]和[111]）的試樣進行低周疲勞試驗，研究了鎳基單晶高溫合金的疲勞小裂紋擴展行為。觀測結果表明，裂紋沿著傾斜于加載方向的主導滑移平面{1 1 1}面擴展。同時為了考察疲勞小裂紋擴展的驅動力，本文對三維斜裂紋進行了有限元建模分析，并利用主導滑移平面上的塑性區尺寸較好地描述了疲勞小裂紋擴展行為。

　　關鍵詞：疲勞小裂紋擴展，鎳基單晶高溫合金，有限元分析，塑性區尺寸，主導滑移平面

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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