通过蠕变曲线的测定及微观组织形貌观察,研究[111]取向镍基单晶合金在高温低应力条件下的组织结构与蠕变行为.结果表明:经完全热处理后,[111]取向单晶合金的组织结构是立方y′相以共格方式嵌镶在y基体中,并沿<100>方向规则排列；在1 040-1 080℃、137～180 MPa的温度和应力范围内,该取向单晶合金表现出明显的温度和施加应力敏感性.蠕变期间,y′相沿与应力轴呈一定角度形成筏状组织,蠕变后期在近断口区域筏状y′相发生粗化和扭折.[111]取向单晶合金在蠕变期间的变形特征是位错在y基体通道中运动和剪切筏状y′相,由于形变量较大,较多位错切入筏状y′相后使其形成亚晶结构,其中,蠕变后期大量位错切入筏状y′相导致合金的蠕变抗力降低,是合金发生蠕变断裂的主要原因.%By means of the measurement of creep curves and microstructure observation, the microstructure and creep behavior of a [111] orientation single crystal nickel-base superalloy were investigated under the conditions of high temperatures and low stresses. The results show that, after full heat-treatment, the microstructure of [111] oriented single crystal nickel-base superalloy consists of the cuboidal γ phase embedded coherently in the y matrix, and regularly arranges along the (100} orientations. In the temperature and stress ranges of 1 040-1 080 'C and 137-180 MPa, the superalloy displays an obvious sensibility to the applied temperatures and stresses. During the tensile creep, the cuboidal γ phase in the alloy is transformed into the rafted structure at a certain angle relative to the direction of the applied stress. Furthermore, the coarsening and distorting of the rafted / phase occurs in the region near the fracture at the latter stage of creep. The deformation features of the [111] orientation single crystal superalloy during creep are that the slipping of the dislocations is activated in the y matrix channels and dislocations shear into the rafted γ phase. The significant amount of dislocations shear into the rafted γ phase, due to the bigger strain occurred to the alloy, to form the subgrain structure during high-temperature creep. In the latter stage of creep, large number of dislocations shear into the rafted γ phase for decreasing the creep resistance, which is thought to be the main reason for the creep rupture of the alloy.
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