通过蠕变性能测试和组织形貌观察,研究了一种Re含量为4.5％Re(质量分数,下同)的镍基单晶合金的高温蠕变行为、变形和损伤机制.结果表明,4.5％Re合金在980℃/300MPa的蠕变寿命为169h.蠕变初期,合金中立方γ'相转变为垂直于应力轴的N型筏状结构.稳态蠕变期间,合金的变形机制为位错在基体中滑移和攀移越过筏状γ'相.蠕变后期,合金的变形机制为位错在基体中滑移和剪切进入筏状γ'相.由于γ基体通道较窄,位错在基体通道中滑移所需的阻力较大.剪切进入γ'相的〈110〉超位错可由{111}面交滑移至{100}面,形成K-W锁,从而抑制位错的滑移和交滑移,这是合金具有较好蠕变抗力的主要原因.主/次滑移位错的交替开动,可致使筏状γ'相扭曲,并促使裂纹在筏状γ/γ'两相界面萌生;裂纹沿垂直于应力轴方向扩展,直至断裂,这是合金的蠕变断裂机制.%By means of creep property measurements and microstructure observations,an investigation has been made into creep behaviors,deformation and damage mechanism of a 4.5％ (mass fraction,the same below) Re-containing,nickel-based single crystal superalloy at 980℃.Results show that,under the condition of 980℃/300MPa,the creep life of 4.5％ Re alloy is 169h.In the initial stage of creep,the cubical γ'phase in alloy is transformed into the N-type rafted structure perpendicular to the stress axis.During the steady stage creep,the deformation mechanism of the alloy is dislocations slipping in γ matrix and climbing over the rafted γ'phase.In the last stage of creep,the deformation mechanism of alloy is dislocations slipping in γ matrix and shearing into the rafted γ phase.On the one hand,the γ matrix channels with narrower feature increases the resistance of dislocations slip ping;on the other hand,the super-dislocations shearing into the rafted γ'phase may cross-slip from {111} plane to {100} plane to form the dislocation configuration of K-W locks,which may restrain the slipping and cross-slipping of dislocations to improve the creep resistance of alloy.Moreover,the alternate activation of the primary/secondary slipping dislocations results in the twisting of the rafted γ'phase to promote the initiation of the cracks on the γ'/γ interfaces,and as the creep goes on,the cracks propagate along the direction perpendicular to the direction of stress axis,up to creep fracture,which is thought to be the fracture mechanism of the alloy during creep.
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