Cyclic behavior of a nickel-based GH4169 superalloy under fully-reversed and asymmetric creep-fatigue tests with strain-controlled is investigated at 650℃. Significant tension–compression asymmetry and continuous cyclic softening are observed for all loading waveforms. The material exhibits mean stress relaxation under asymmetric loading and fully-reversed loading with valley strain dwells. Moreover, stress relaxation behavior during the dwell period is almost independent of the number of cycles. In order to identify the deformation mechanism, the evolutions of mean value and amplitude of the internal stress (back stress and effective stress) based on the partition of hysteresis loops are analyzed. Results show that both the cyclic softening and mean stress relaxation are primarily dominated by the evolution of back stress and secondarily affected by that of effective stress. Such findings lay a solid foundation for further investigations of reasonable cyclic deformation description and accurate life prediction in GH4169 alloy under creep-fatigue loadings.

研究了镍基GH4169高温合金在650℃下完全反向和不对称蠕变疲劳试验及应变控制下的循环行为。在所有加载波形中均观察到明显的拉伸-压缩不对称和连续循环软化。该材料在不对称载荷和完全逆向载荷（具有谷形应变滞留）下表现出平均应力松弛。此外，在保压期间的应力松弛行为几乎与循环次数无关。为了确定变形机理，分析了基于磁滞回线划分的内部应力（背应力和有效应力）的平均值和幅度的变化。结果表明，循环软化和平均应力松弛均主要由背应力的演化决定，其次受有效应力的影响。这些发现为进一步研究GH4169合金在蠕变疲劳载荷下的合理的循环变形描述和准确的寿命预测奠定了坚实的基础。