采用热机械疲劳试验、扫描电镜、透射电镜等方法研究了一种镍基单晶高温合金在600～900 ℃的同相位热机械疲劳行为。结果表明: 该合金在试验中承受的平均应力表现为压应力; 随着机械应变幅的增大, 疲劳寿命逐渐下降, 应力范围和塑性应变量逐渐增大; 合金在试验中表现为高温半周循环软化、低温半周循环硬化; 合金热机械疲劳的主要变形机制为a/2〈11-0〉{111}型位错在基体内的滑移和交滑移运动; 合金的断裂方式为微孔聚集型断裂, 拉应力对合金的断裂起到了主导作用。

The in-phase thermo-mechanical fatigue (IP TMF) behaviors in a temperature range of 600-900 ℃ for a nickel-base single crystal superalloy were studied by using scanning electron microscope (SEM), transmission electron microscope (TEM) and IP TMF test. The results show that the mean stress was compressive stress in the test. With the mechanical strain amplitude increasing, the fatigue life decreased, but the stress range and the plastic strain increased gradually. In the high temperature half cycle, this alloy displayed a cyclic softening. In contrast, the alloy showed a cyclic hardening in the low temperature half cycle. The main mechanism for IP TMF of the alloy was glide and cross-glide of a/2〈11-0〉{111} dislocation in γ phase. The cracks initiated from micro-pores and propagated until the alloy fractured. The tensile stress played a leading role in the fracture of alloy.