一种镍基单晶合金的拉伸蠕变特征

Tensile Creep Characteristic of a Single Crystal Nickel Base Superalloy

研究了[001]取向镍基单晶高温合金的高温拉伸蠕变性能，通过SEM、TEM观察分析了相的形貌演化及合金的变形机理．结果表明：在980～10200C／200～280MPa条件下蠕变曲线均由初始、稳态及加速蠕变阶段组成；在拉伸蠕变期间γ’强化相由初始的立方体形态演化为与应力轴垂直的N-型筏形状；初始阶段位错在基体的八面体滑移系中运动，稳态阶段不同柏氏矢量的位错相遇，发生反应形成位错网；蠕变末期，应力集中致使大量位错在位错网破损处切入筏状γ’相是合金发生蠕变断裂的主要原因．

In this paper, the creep property at different temperatures and stresses, the morphology evolution of γ＇ phase, deformation characteristic and creep fracture mechanism are investigated in improved D29 single crystal nickel-base superalloy with the orientation [001 ]. The conclusions can be drawn as following： Under the condition of 980 - 1 020℃/200 -280MPa, the creep curves consist of three stages. In the primary stage of creep at high temperature and low stress, the structure feature of the γ＇ phase is that the cubic γ＇ phase transforms into the lamellar raft structure, the deformation mechanism is the dislocation movement in the octahedral slip systems of the matrix channel, the dislocation network forms when dislocations meet and react from two directions. The deformation mechanism is the dislocation climbing over the γ＇ rafts during the steady creep stage. The main reason for creep fracture is that a large number of dislocations shearing into the γ＇ rafts from the γ/γ＇ phase interfaces where the dislocation networks are damaged at the later creep stage.