High total strain-controlled creep-fatigue tests of 1.8% were performed for a directionally-solidified Ni-based superalloy, DZ445, at 900 °C in air. Dwell times of 0, 2, and 5 min. were introduced at the tensile peak strain for each cycle. Experimental results show a decrease in fatigue life with increasing dwell time. The significant cyclic softening is observed after the application of the dwell time. The mean compressive stress and large plastic-strain accumulation are produced due to the stress relaxation in the tensile-dwell period, resulting in the increase of the hysteresis loop area. The typical single-source crack-initiation and transgranular crack-propagation are transformed into multi-source crack-initiation and mixed transgranular and intergranular crack-propagation mode by these characteristics. Dislocation features are transformed from cutting of γ' precipitates by multiple stacking faults to the mixed mode of dislocation climbing and slipping. The reduction in the fatigue life with increasing the dwell time is well explained on the basis of the mechanical response and damage mechanism. The fatigue life is also predicted by the energy-based life-prediction model.

在900°C的空气中，对定向凝固的Ni基高温合金DZ445进行了1.8％的高总应变控制蠕变疲劳试验。停留时间为0、2和5分钟。在每个循环的拉伸峰值应变处引入抗拉强度。实验结果表明，疲劳寿命随停留时间的增加而降低。在施加停留时间后，观察到明显的循环软化。由于在拉伸停留期间的应力松弛而产生平均压缩应力和大的塑性应变累积，从而导致磁滞回线面积的增加。这些特征将典型的单源裂纹萌生和跨晶裂纹扩展转变为多源裂纹萌生和混合的跨晶和晶间裂纹扩展模式。位错特征从多个堆积断层对γ'沉淀物的切割转变为位错爬升和滑移的混合模式。根据机械响应和损坏机理，可以很好地说明随着停留时间的增加而导致的疲劳寿命的降低。疲劳寿命也可以通过基于能量的寿命预测模型进行预测。