单晶镍基高温合金超高温蠕变期间的变形机制

Deformation Mechanism of Single-Crystal Nickel-based Superalloys During Ultra-High-Temperature Creep

摘要:

通过蠕变性能测试及组织形貌观察，研究了6%Re-5%Ru（质量分数）单晶镍基高温合金的超高温蠕变行为和变形机制。结果表明，该合金在1160 ℃/120 MPa条件下的蠕变寿命为206 h。稳态蠕变期间，位错在基体中滑移和攀移越过筏状γ′相是合金的变形特征，基体中溶解的高浓度难熔元素可增加位错运动阻力。蠕变后期，切入筏状γ′相的位错可由｛111｝面交滑移至｛100｝面，形成Kear-Wilsdorf（K-W）位错锁，高数量K-W位错锁可抑制位错滑移和交滑移，是合金具有较好蠕变抗力和较低应变速率的原因。交滑移可扭曲筏状γ′相，并在两相界面发生裂纹萌生与扩展，直至断裂，这是合金蠕变后期的变形与损伤特征。其中，溶入γ′相的Ru原子可替换Al原子，合金中Ru与Re、W的相互作用使较多的Re、W原子溶入γ′相，延缓元素扩散速率，阻碍位错运动，使合金在超高温蠕变期间仍保留高数量K-W位错锁及良好蠕变抗力。

Abstract:

The creep behavior and deformation mechanism of the nickel-based single-crystal superalloy containing 6wt% Re and 5wt% Ru at ultra-high temperatures were studied via microstructure observation and creep property analysis. The results show that under the condition of 1160 °C/120 MPa, the Ni-based superalloy has a creep life of 206 h. During the steady state creep period, the deformation mechanism is dominated by dislocation glide in the γ matrix and dislocation climb over the γ′ raft phases. The refractory elements dissolved in the γ matrix can improve the resistance to dislocation movement. In the late creep stage, the cross-slip occurs from {111} plane to the {100} plane with the dislocations used for shearing the γ′ phase, and then the Kear-Wilsdorf (K-W) dislocation locks are formed. A large number of K-W dislocation locks can inhibit the dislocation glide and cross-slip, thus improving the creep resistance and reducing the strain rate for Ni-based superalloys. In the late creep stage, the cross-slip dislocations are initiated to twist the γ′/γ raft phases, and the crack initiation and propagation occur in the γ′/γ interfaces until fracture. These phenomena are the damage and fracture features of the Ni-based superalloys. The Ru atoms dissolved in the γ′ phase can replace the Al atoms. When Ru, Re, and W atoms react in the Ni-based superalloy, more Re and W atoms can be dissolved into the γ′ phase, which reduces the element diffusion rate and hinders the dislocation movement, thereby retaining more K-W dislocation locks and excellent creep resistance of Ni-based superalloys at ultra-high temperatures.