[110]取向DD3镍基单晶合金的组织结构及蠕变行为

Microstructure and Creep Behavior of DD3 Single Crystal Nickel-base Superalloy with [110] Orientation

通过蠕变曲线的测定及微观组织观察,研究了[110]取向镍基单晶合金的组织结构与蠕变行为。结果表明,经完全热处理后,合金中立方γ′相沿〈100〉取向规则排列;蠕变期间合金中形成筏状γ′相的取向与应力轴方向成45°角,蠕变后期在近断口区域筏状γ′相发生扭折。在1040℃、137MPa条件下,合金在稳态蠕变期间具有较高的应变速率和较短的蠕变寿命,而蠕变期间的变形特征是位错在γ基体通道中滑移和剪切筏状γ′相;其中,γ′相形成筏状结构后,沿与应力轴成45°角的基体通道承受最大剪切应力,使蠕变位错易于在基体通道中滑移,是使合金具有较大应变速率的主要原因。

By means of the measurement of creep curves and microstructure observation,an investigation has been made into the microstructure and creep behaviors of [110] oriented single crystal nickel-base superalloy.Results show that after full heat treated,the cubic γ' precipitating in the alloy is coherently embedded in the γ' matrix and regularly arranged along the 〈100〉 orientation.During creep,the cubic γ' phase in the alloy is transformed into the rafted structure at 45° angle relatived to the applied stress axis direction.In the further,the distortion of the rafted γ' phase occurs in the region near the fracture in the later stage of creep.Under the condition of the applied stress of 137MPa at 1040℃,the alloy displays a higher strain rate during steady state creep and shorter creep lifetime.The deformation feature of the alloy during creep is that the slipping of the dislocations are activated on the γ'matrix channels and the dislocations shear in the rafted γ' phase.Thereinto,after the rafted γ' phase is formed,the maximum of the shearing stress is applied along the γ' matrix channels of 45° angle relatived to the applied stress axis,and making the dislocations slipping easily along the γ'matrix channel,which is thought to be the main reason of the alloy having higher strain rate and shorter creep lifetime.