Structure Evolution and Creep Behavior for a Nickel-Base Single Crystal Alloy along [011] and [001] Orientations

摘要:

研究980 ℃，200 MPa拉伸蠕变期间[001]和[011]取向镍基单晶合金中γ′相的形貌演化及蠕变特征，在相同拉伸条件下晶体取向的变化对合金的应变和应变速率产生明显影响。结果表明：沉淀相的定向粗化方向取决于合金的晶体取向，沿[001]取向拉伸，γ′相从最初的立方形态转化为与拉伸应力轴垂直的筏形；当拉伸轴平行于[011]取向时，γ′ 相沿[010] 和[100] 方向扩散生长，演化成与拉伸轴倾斜45o角的筏形。[011]取向合金的蠕变强度随其基体通道宽度的增大而快速下降，蠕变前期[001]与[011]取向的应变速率相近，蠕变后期合金表现出明显的蠕变各向异性

Abstract:

The morphology evolution and creep behavior of g ￠ phase in [001] and [011] oriented specimens of a nickel-base single crystal superalloy during the tensile creep at 1253 K and 200 MPa were investigated. SEM and TEM observation shows that the direction coarsening of precipitates is highly dependent on the crystal orientation. In [001] orientation, the g ￠ phase transits from original cuboids to the raft-shape along the perpendicular direction to the tensile stress axis while in [011] orientation the g ￠ phase develops along the [010] and [100] and evolves into a raft with inclined 45° angle to the tensile stress axis. The strain rates for [001] and [011] orientations are almost equal at the earlier stage of creep. With the matrix channel broadening, the strain rate for [011] orientation increases gradually, while the creep strength decreases rapidly. Based on the evolutional rule of g ￠ phase and the creep curves, the anisotropic creep behavior is obvious at the later stage of steady-state and the tertiary creep stage