含Re镍基单晶高温合金高温低应力蠕变初期γ/γ′界面结构研究

Study of the γ/γ′ interfacial structure during the primary creep stage of high-temperature and low-stress creep in a Re doping nickel-based single crystal superalloy

为了深入理解含Re镍基单晶高温合金高温低应力蠕变初期的蠕变行为和强化机制,本文利用电子显微学和能谱学等方法,从介观至原子尺度研究了DD6单晶高温合金在1100℃/140 MPa蠕变15 min后的界面位错组态、界面位错核心结构以及界面位错附近的合金元素分布情况.结果表明蠕变初期合金中的位错密度较低,只在局部形成位错网络,因此蠕变初期γ此蠕变界面形成的V形和台阶状凸起结构数量明显低于稳态蠕变初期(12h)时的,而且台阶状凸起结构(对应a/2<101>60°混合型位错)明显多于V形凸起结构(对应a/2<110>刃型位错,由位错反应形成).蠕变初期形成的特殊形状的台阶状凸起结构是由于界面位错沿γ/γ′界面运动形成的,而Re等合金元素的共偏聚进一步验证了Re元素偏聚同界面位错的交互作用.

For deeply understanding the creep behavior and the strengthening mechanism of Re doping nickel-based single crystal superalloys during the primary creep stage of high-temperature and low-stress creep, electron microscopy and energy dispersive X-ray spectroscopy are used to study the γ/γ′ interfacial structure from mesoscopic to atomic scale in the DD6 single crystal superalloy crept for 15 min under 1100°C/140 MPa. The dislocation configuration, the core structure of interfacial dislocations and the elemental distribution around the interfacial dislocations have been carefully investigated. It is shown that the dislocation density is relatively low during the primary creep, and the dislocation networks are only locally formed. Thus fewer interfacial protrusions are formed compared to the stable creep stage（12 h）, and more step-like protrusions（corresponding to the a/2〈101〉60° mixed dislocations） have been observed than the V-shaped protrusions（corresponding to the a/2〈110〉 edge dislocations which are formed by dislocation reaction）. The special configuration of the step-like protrusions during the primary creep stage are formed by the dislocation motion along the γ/γ′ interface and co-segregation of Re with other alloying elements could help to confirm the interaction of Re segregation with interfacial dislocations.