分别制备了[001]和[011]取向的Ni-Co-Cr-Mo-w-Al-Ti-Ta镍基单晶高温合金试样.在750℃/750 MPa条件下,[001]取向合金的平均蠕变寿命叫显高于[011]取向合金,[011]取向合金延伸率稍高.在982℃/248 MPa条件下,[001]取向合金的平均蠕变寿命和延伸率均高于[011]取向合金,各向异性上要表现在加速蠕变阶段,但各向异性程度比低温高应力时显著降低.存高温低应力条件下,2种取向合金中γ'相均已形筏,[001]取向合金的筏化方向垂直于应力轴,而[011]取向合金的筏化方向与应力轴的夹角约为45°.γ'相形筏后,阻碍了位错运动,导致加工硬化,因此,γ'相筏化是各向异性程度降低的主要原因.在[011]取向合金的蠕变后期观察到挛品组织同时穿越γ和γ'相,导致试样塑性人幅度降低,迅速断裂.
Constant load creep tests were performed on the [001] and [011] oriented Ni-Co-Cr Mo W A1 Ti-Ta single crystal superalloys. The [001] oriented alloy has much longer creep lifc than that of [011] oriented alloy, but the elongation of [011] oriented alloy is slightly higher under the condition of 750 ℃/750 Mpa. The average creep life and elongation of [001] oriented alloy are both higher than that of [011] oriented alloy at 982 ℃/248 Mpa, and the anisotropy occurs mainly during the accelerating creep stage, but anisotropic degree decreases obviously. The SEM analysis reveals γ' phases are rafted in the two directions, which blocks the glide/climb of dislocations and causes creep hardening, the rafting of γ' phase is the dominant reason to decrease of crccp anisotropy at higher temperature. The TEM observation indicates deformation twins formed in [011] oriented alloy, whichlowers the plasticity of the sample and induces the sample to fracture rapidly.
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