论文部分内容阅读
通过进行具有拉伸保持、压缩保持和拉－压保持的全反向总应变控制的低周疲劳实验，对镍基高温合金ＧＨ４０４９的蠕变－疲劳交互作用行为进行了系统的研究。结果表明，在较高的总应变幅下，合金首先发生循环应变硬化而后则发生软化直至断裂，而在低的总应变幅下则表现为循环稳定。由于压缩应变保持和拉－压应变保持的介入，合金的疲劳寿命将显著降低，但拉伸应变保持对疲劳寿命的影响则取决于总应变幅。拉伸保持或压缩保持时将分别产生平均压应力或拉应力。扫描电镜断口观察结果表明，裂纹萌生和第Ⅰ阶段的扩展均为穿晶形式，而第Ⅱ阶段的裂纹扩展则主要为沿晶形式。此外，利用线性累积损伤法则对蠕变－疲劳寿命进行了预测。
The creep-fatigue interaction of Ni-based superalloy GH4049 was systematically investigated by low-cycle fatigue test with total reverse total strain control with tensile holding, compression holding and pull-hold. The results show that, at higher total strain amplitude, the alloy first undergoes cyclic strain hardening and then softens until fracture, while at low total strain amplitude, it shows cyclic stability. The fatigue life of the alloy will be significantly reduced due to the compressive strain retention and pull-compressive strain retention, but the effect of tensile strain on fatigue life depends on the total strain amplitude. Tensile hold or compression hold will produce average compressive or tensile stress, respectively. Scanning electron microscopy fracture observations show that the crack initiation and the first phase of the expansion are transcrystallization, while the second phase of the crack growth is mainly the intergranular. In addition, creep-fatigue life is predicted using the linear cumulative damage law.