镍基单晶合金高温蠕变变形与损伤行为

Deformation and Damage Behavior of Single Crystal Nickel-based Superalloy During Elevated Temperature Creep

通过蠕变性能测试和组织观察,研究了镍基单晶合金在高温蠕变期间的变形和损伤行为。结果表明,该合金在1040℃/137MPa条件下的蠕变寿命为556 h,表现出优异的蠕变抗力。合金在稳态期间的蠕变特性是位错在γ基体中滑移和攀移越过筏状γ′相。在蠕变后期,合金的变形特征是位错剪切进入筏状γ′相,剪切γ′相的位错可以交滑移,形成的Kear-Wilsdorf(K-W)锁可抑制位错的滑移和交滑移。位错的交滑移能够促使筏状γ/γ′两相的扭曲,致使沿γ/γ′界面的裂纹萌生及界面断裂,这是合金的损伤和断裂特征。而σ>η/α被认为是裂纹发生失稳扩展的条件。

The deformation and damage behavior of the single crystal Ni-based alloy during elevated temperature creep were investigated through analyzing creep properties and microstructure. The results show that the creep life of Ni alloy under the condition of 1040 ℃/137 MPa is 556 h, displaying an excellent creep resistance of Ni alloy. The creep feature of Ni alloy at steady state is the dislocation glide in γ phase and dislocation climb over the γ′ rafts. In the late stage of creep, the deformation feature of Ni alloy is that the γ′ rafts are sheared by the dislocations of cross-slip, which forms the Kear-Wilsdorf(K-W) locks to restrain the dislocation glide and cross-slip dislocation. The cross-slip dislocations cause the distortion of γ/γ′ rafts, thereby promoting the initiation of cracks along the γ′/γ interfaces and the interface fracture, which is the damage and fracture features of Ni alloy. The condition of σ > η/α is considered as the prerequisite for unstable crack propagation.