不同取向镍基单晶高温合金的蠕变参数及其与蠕变行为的关系研究

Creep Parameters of Single Crystal Nickel-Base Superalloys with Different Orientations and Their Relationship with Creep Behavior

通过蠕变性能的测试和内摩擦应力的测定,研究了[001]、[011]和[111]取向镍基单晶高温合金分别沿[001]、[011]和[111]取向在高温/低应力条件下拉伸蠕变至稳态阶段的有效蠕变参数及其与蠕变性能和变形机制之间的关系。结果表明,随着温度的升高和外加应力的降低,3种取向合金的内摩擦应力降低。在相同条件下,3种取向合金的内摩擦应力顺序为σ_(i[001])>σ_(i[111])>σ_(i[011])。蠕变前后[011]和[111]取向合金内相对于应力轴倾斜连贯的"屋脊"型基体通道是2种合金具有较低内摩擦应力和较差蠕变抗力的重要原因。[001]取向合金在1040℃/137 MPa条件下的有效蠕变激活能为Q_(e[001])=281.32 kJ/mol,表明其稳态阶段的变形机制为元素扩散控制的位错攀移。[011]取向合金的有效蠕变激活能为Q_(e[011])=146.87 kJ/mol,其较低的数值与其内部开放的基体通道对位错滑移较小的阻碍作用有关;[111]取向合金较[011]取向合金较高的有效蠕变激活能Q_(e[111])=182.61 kJ/mol与其内部片层状的γ′相和位错的交滑移有关。

The effective creep parameters of the [001]-, [011]- and [111]-oriented single crystal nickel-base superalloys after being crept to steady-state stage under the conditions of high temperatures/low stresses along [001], [011] and [111] orientations, respectively, and their relationship with the creep performance and deformation mechanism were studied by the tests of creep performance and the measurements of internal friction stresses. Results show that with the increase of creep temperatures and the decrease of applied stresses, the internal friction stresses of the three alloys decrease. Under the same conditions, the order of the internal friction stresses is σi[001] 〉 σi[111] 〉 σi[011]. The inclined and continuous ＂roof＇-type 7 channels in the [011]- and [111]-oriented alloys before and after creep are responsible for the low internal friction stress and poor creep resistance of the two alloys. The effective creep activation energy of the [001]-oriented alloy is Qe[001]= 281.32 kJ/mol, indicating that the deformation mechanism during steady-state creep stage is the dislocation climb controlled by element diffusion. The effective creep activation energy of the [011 ]-oriented alloy is Qe[011]= 146.87 kJ/mol, and the low value is related to the open γ matrix channels possessing small resistance for dislocation slip. The effective creep activation energy of the [111]-oriented alloy is Qe[111]= 182.61 kJ/mol, and the larger value than that of the [011]-oriented alloy is related to the lamellar y rafts and the cross slip of dislocations in the [111]-oriented alloy.