通过蠕变性能测试、组织形貌观察及位错组态的衍射衬度分析, 研究了镍基单晶高温合金在中温/高应力稳态蠕变期间的变形机制. 结果表明, 在760 ℃, 760 MPa和800 ℃, 650 MPa蠕变期间, 剪切γ′相的位错可发生分解, 分解后领先的α/3<112>超点阵Shockley不全位错切入γ′相, 拖曳的α/6<112>Shockley不全位错滞留在γ′/γ相界面, 2个不全位错之间形成超点阵内禀堆垛层错(SISF); 此外, 剪切进入γ′相的超点阵位错可由{111}面交滑移至{100}面, 形成具有非平面位错芯结构的K-W锁, 可抑制位错的滑移和交滑移, 提高合金的蠕变抗力. 在850 ℃, 500 MPa蠕变期间, 合金中的层错消失, 部分剪切进入筏状γ′相的α<110>超点阵位错可分解形成“2个α/2<110>不全位错加反相畴界(APB)”的组态, 而合金中K-W锁的消失是由高温热激活致使立方体滑移的位错重新交滑移至八面体所致.

Ni-based single crystal (SC) superalloys have been widely used to produce turbine blades of aeroengines, but under the action of centrifugal force, creep damage is still the main failure mode. In service, the blades experience multiple cycles of various conditions of high temperatures, low stresses and intermediate temperatures, high stresses, and due to effective and efficient means of cooling and insulating the blades during operation, the actual temperature the blades bear can be smaller than the working temperature at the hot ends of aeroengines, so the systematical study on the creep behavior of SC superalloys at intermediate temperatures, high stresses is significant. It is generally considered that dislocations cutting γ′ phase is the main deformation mechanism of SC alloys at intermediate temperatures, high stresses, and dislocations cutting into γ′ phase can be decomposed into different configurations for different alloy systems, even under similar conditions. Moreover, large amount of dislocations cutting into γ′ phase means the degradation of creep performance of the alloys, so it is significant to study the cutting modes of dislocations. In this work, by means of creep tests, TEM observations and diffraction contrast analysis of dislocations, the deformation mechanisms of a Ni-based SC superalloy during steady-state creep at intermediate temperatures, high stresses are studied. Results show that, under the conditions of 760 ℃, 760 MPa and 800 ℃, 650 MPa, dislocations cutting into γ′ phase are decomposed to form partial dislocations plus superlattice intrinsic stacking faults (SISF). Thereinto, the leading α/3<112> super Shockley partial dislocations cut into γ′ precipitates, while the dragging α/6<112> Shockley partial dislocations remain at γ′/γ interfaces, and between them there exists SISF. Additionally, super dislocations shearing into γ′ phase can cross slip from {111} to {100} crystal planes to form Kear-Wilsdorf (K-W) locks with non-plane dislocation core structure, which can inhibit the slip and cross slip of dislocations to enhance the creep strength of the alloy. At 850 ℃, 500 MPa, stacking faults disappear in the alloy, and some a<110> super dislocations cutting into γ′ rafts can be decomposed to form the configuration of two partial dislocations with Burgers vector of α/2<110> plus antiphase boundary (APB), and K-W locks are released for high-temperature thermal activation results in the cross slip of dislocations from cubic slip systems to octahedral ones.