The bars of single crystal superalloy DD6 were prepared with withdrawing rates of 2mm/min, 4.5mm/min, 7mm/min. The low cycle fatigue properties of alloy with different with drawing rates were studied comprehensively at 650℃. The fatigue fracture morphology and microstructure were investigated using SEM and TEM. The results show that with the increasing of withdrawing rate, the size of γ' precipitates decreases and quadratic dendrite arm spacing developed gradually. Primary dendrite arm spacing is little related to withdrawing rate. Alloy with the withdrawing rate of 4.5mm/min has the longest low cycle fatigue among the withdrawing rates. It was founded that DD6 alloy exhibited cycle stability at most strain amplitude. The fatigue crack favorably initiated at the sub-surface, and reduced along with the strain amount. The fatigue propagation characteristics of the first stage changed from cleavage-like fatigue facet into ragged fatigue facet. Fatigue crack extended along one or more {111} sliding surfaces.%采用2mm/min,4.5mm/min和7mm/min的抽拉速率制备了DD6单晶高温合金试棒.研究了抽拉速率对合金650℃低周疲劳性能的影响.利用扫描电镜(SEM)和透射电镜(TEM)分析了疲劳试样的断口形貌和微观组织.研究结果表明:随抽拉速率的增大,γ’相尺寸减小,一次枝晶间距差异不大,二次枝晶呈发达的趋势.抽拉速率4.5 mm/min的合金650℃低周疲劳寿命最长.DD6合金表现为基本稳定的循环应力响应行为.疲劳裂纹主要萌生于试样亚表面,随应变量降低,裂纹扩展第一阶段断裂特征由类解理断裂面向锯齿状断面转变.疲劳裂纹沿一个或者多个｛111｝滑移面扩展.
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