短期时效对DD6镍基单晶高温合金γ'相析出行为的影响

Effect of Short-Term Aging Treatment onγ'Phase Precipitation Behavior in DD6 Single Crystal Superalloy

通过高分辨透射电子显微镜和扫描电子显微镜揭示了不同冷速对二代镍基单晶高温合金DD6的组织演化的影响。结果表明,在空冷条件下,基体通道处分布着大量二次γ'相,随时间的延长,其形貌由球形→立方形→蝴蝶状,尺寸也随之增加;γ'相边缘出现裂缝并逐渐演化为锯齿状凹槽。在炉冷条件下,基体通道中分布大量细小的球状二次γ'相,基体通道宽度变窄,并与保温时间呈负相关。在水冷条件下,基体通道中无二次γ'相分布,γ'相立方度完整,随保温时间延长,形貌无明显变化。γ'相在择优分解的过程中,在两相界面间产生大量正负刃型位错,相界两侧的正负刃型位错相遇产生湮灭,降低周围的能量,促进了γ'相的择优分解。

The effects of different cooling speeds on the microstructure evolution of second-generation nickel-based single crystal superalloy DD6 were revealed by high-resolution transmission electron microscopy and scanning electron microscopy.Results show that under air-cooling conditions a large number of secondaryγ'precipitates are distributed at the matrix channels.The secondaryγ'precipitates progressively evolve from spherical to cuboidal and then to butterfly-like shapes.And the size also increases with time.Sharp crevices appear at the edges of theγ'precipitates and gradually evolve into serrated grooves.Under furnace-cooling conditions,a large number of fine spherical secondaryγ'precipitates are distributed in the collective channel,and the width of the matrix channel decreases and is negatively correlated with the holding time.Under water-cooling conditions,there is no secondaryγ'precipitate in the matrix channel.The cubicity ofγ'precipitates is complete,and there is no significant change in morphology with the prolongation of the holding time.γ'precipitates produce a large number of positive-negative edge-type dislocations between the two-phase interfaces in the process of selective decomposition.The positive-negative edge-type dislocations on the two sides of the phase boundary meet,producing annihilation,which reduces the surrounding energy and promotes the selective decomposition of theγ'precipitates.