镍基高温合金DZ125的单边缺口蠕变行为

Single-edge notched creep behavior of Ni-based superalloy DZ125

为了研究非对称结构特征导致复杂应力状态下的蠕变持久问题,本文通过DZ125合金单边缺口平板试件的蠕变试验,揭示了非对称结构特征作用下持久性能的弱化效应;通过分析缺口试件的裂纹起裂机理,发现缺口根部区域蠕变裂纹萌生是缺口根部应力集中和枝晶间组织缺陷共同作用的结果;基于耦合KR蠕变损伤的黏塑性本构理论,分析了蠕变松弛后缺口根部截面截然不同的应力分布特征;结合观测到的试件裂纹萌生和断口形貌规律,证实了单边缺口带来的附加弯矩加剧了缺口根部附近区域塑性变形的累积过程,缺口平分面上的压应力区域与断口瞬断特征能较好地关联。

In order to study the problem of creep persistence under complex stress conditions caused by the asymmetric structure characteristics, this paper performed creep tests on single-edge notched flat specimens of Nibased superalloy DZ125, and revealed the weakening effect of the endurance performance under the action of the asymmetric structure characteristics. According to the analysis of the crack initiation mechanism of the notched specimens, it is found that the creep crack initiation at the root of the notch is due to both the stress concentration at the root of the notch and the structural defects between the dendrites. Based on the visco-plastic constitutive theory coupled with K-R creep damage law, the completely different stress distribution characteristics of the notch root section after loading and creep relaxation is revealed. Combined with the observed crack initiation and fracture morphology of specimens, the additional bending moment caused by the single-edge notched specimen aggravates the plastic deformation accumulation process area near the notch root. At the same time, the compressive stress area on the bisector of the notch can be better related to the instantaneous fracture characteristics of the fracture.