于兴福，杜洪强,，田素贵，宁 英，王铁军，崔树森

(1. 沈阳工业大学 材料科学与工程学院，沈阳 110870；2. 沈阳黎明航空发动机股份有限公司，沈阳 110043)

无铼二代镍基单晶高温合金中温高应力蠕变机制

于兴福1，杜洪强1,2，田素贵1，宁 英2，王铁军2，崔树森2

(1. 沈阳工业大学 材料科学与工程学院，沈阳 110870；2. 沈阳黎明航空发动机股份有限公司，沈阳 110043)

通过测定一种镍基单晶合金的蠕变曲线和观察微观组织及对合金断裂后位错组态进行分析，研究中温高应力条件下镍基单晶合金的组织演化及断裂特征。结果表明：在760 ℃、700 MPa条件下，合金蠕变断裂后的断口表面由类台阶状形貌组成，且台阶取向相同，台阶的两个棱边与〈110〉晶向平行，台阶的上平面平行于{001}晶面。合金凝固形成的共晶区是合金薄弱区域，裂纹在该区域萌生和扩展，并最终导致合金的蠕变断裂。800 ℃、750 MPa蠕变期间，合金中的γ ′相可形成与应力轴垂直的类N−型筏状结构，但筏状γ ′相的尺寸较短，在合金的γ基体通道及γ ′/γ两相界面处存在大量位错网，有部分〈110〉超位错切入筏状γ ′相内。(1/2)位错由γ ′/γ相界面切入γ ′相后发生位错分解，可形成(1/3)〈112〉超肖克莱不全位错+层错的位错组态，当有单个位错穿过层错区时，致使位错与层错衬度相互重叠，使层错条纹明暗衬度发生变化。

单晶镍基高温合金；断口表面；蠕变；组织演化；位错

Abstract:By measuring the creep curves, observing the microstructure and analyzing dislocation configuration of the nickel-base single crystal superalloy after being fractured at medium temperature and high stress, the rupture fracture surface characters and deformation mechanism of the nickel-base single crystal superalloy were studied. The results show that, the rupture fracture surface is made of lots of steps plane, which posses the same orientation and two edges with〈110〉 orientation for each step, and the upper plane of step parallel to the {001} plane faces after creep up to fracture at 760 ℃ and 760 MPa. The formed eutectic area during lasting solidification is the weak area where the crack initiation and propagation happen during creep, eventually lead to alloy creep rupture. The formed N-shape like ordered γ ′ phase structure vertical to the stress axis during creep at 800 ℃ and 750 MPa, but the raft length of ordered γ ′ phase is shorter.There are lots of dislocation nets in matrix channel and ordered γ ′/γtwo-phase interface place, and a part of 〈110〉 super dislocations shear the ordered γ ′ phase raft. The dislocation is decomposition into partial dislocation (1/3)〈112〉 + stacking fault configuration when the (1/2)dislocation shears the γ ′ phase through γ ′/γ phase interface. When a single dislocation slips through the stacking fault area, the dislocation and stacking fault overlap, and the dislocations lining stripe light and shade changes.

Key words:single crystal nickel-base superalloy; fracture surface; creep; microstructure evolution; dislocation

单晶叶片在服役期间所受的离心应力远低于合金的屈服强度，但蠕变现象依然存在，由于合金在不同条件下具有不同的蠕变特征，并与蠕变寿命密切相关[1−5]，因此，单晶合金的蠕变及断裂行为得到广泛的研究[6−12]。……