应变幅对第二代镍基单晶高温合金DD11980℃低周疲劳性能的影响（英文）

Effect of Strain Amplitude on Cyclic Deformation Behavior of Nickel-Based Single Crystal Superalloy DD11 in Low Cycle Fatigue

通过对第二代镍基单晶高温合金DD11在980℃条件下低周疲劳性能测的试及表征,研究了不同应变幅(Δε/2=0.5%～1.2%)对循环应力响应行为和断裂模式的影响,建立了显微组织演变和疲劳行为之间的联系。结果表明,该合金发生了循环软化行为并且随着应变幅的提高,循环软化程度降低。γ'的粗化以及垂直于加载轴方向的γ通道加宽有利于位错运动的进行,因此造成了循环软化。当应变幅为0.5%时,位错回复也是造成循环软化的原因。随着应变幅增加至0.8%后,γ'的粗化以及垂直于加载轴方向的γ通道加宽程度降低,位错在两相界面上发生了塞积,造成了循环软化程度的降低。疲劳失效模式从扩展区的正断模式转变为了瞬断区的剪切断裂模式。本研究有利于建立单晶高温合金涡轮叶片疲劳失效模式、循环应力响应行为和组织三者的关系,对涡轮叶片的设计使用具有一定的指导意义。

The cyclic stress response behavior and failure modes of nickel-based single crystal superalloys DD11 with [001] orientation in low cycle fatigue at 980 oC and strain amplitude range of 0.5%~1.2% were investigated. The relationship between deformation microstructure and fatigue behavior was established. The results show that cyclic softening occurs and the softening degree decreases with increasing the strain amplitude. The coarsening of γ’ and the broadening of transverse channels of γ are liable to cause the movement of dislocation in the γ channel and result in cyclic softening. Moreover, the dislocation recovery occurs at the low strain amplitude, which also causes cyclic softening. The pilling-up of dislocation occurs at the γ/γ’ interfaces as the degree of coarsening γ’ and broadening transverse channels of γ decreases when the strain amplitude is large than 0.8%, which results in a decrease in the degree of cyclic softening. The fatigue failure mode changes from normal fracture to shear fracture, corresponding to the transition of crack from stable propagation to the instant fracture.