研究了第三代单晶高温合金 DD9在800℃的高周旋弯疲劳性能，并用扫描电镜和透射电镜分析了其断口形貌和断裂机制。结果表明：DD9合金在800℃的高周旋弯疲劳性能优异；疲劳裂纹起源于试样表面、亚表面的滑移带、氧化物、显微疏松处，沿{111}面扩展，断裂机制为类解理断裂，断口上有典型的疲劳条带；断裂后，γ′相的形状没有发生改变，沿滑移带形成了二次裂纹，位错密度分布不均匀；位错主要在基体通道中通过交滑移扩展运动。
Rotary bending high cycle fatigue properties of the third generation single crystal superalloy DD9 were investigated at 800 ℃.SEM and TEM were used to study fracture surface morphology and fracture mechanism of the alloy.The results show that the rotary bending high cycle fatigue properties of DD9 alloy were excellent.The fatigue crack initiated slip band,oxide and microporosity at or near the surface.Crack propagated along {1 1 1 }octahedral slip planes and the fracture mechanism was quasi-cleavage fracture.The γ′ phase still maintained same shape after fracture,the secondary crack formed along the slip band,and dislocation density distributed unevenly. The dislocation moved mainly by cross-slip in substrate channel.
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