Creep of Single Crystals of Nickel-Based Superalloys at Ultra-High Homologous Temperature
Creep of Single Crystals of Nickel-Based Superalloys at Ultra-High Homologous Temperature
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DOI：
10.1007/s11661-018-4729-6
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发表时间：
2018-06
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通讯作者：
A. Epishin;B. Fedelich;G. Nolze;S. Schriever;T. Feldmann;M. Ijaz;B. Viguier;D. Poquillon;Y. Bouar;A. Ruffini;A. Finel
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作者：
A. Epishin;B. Fedelich;G. Nolze;S. Schriever;T. Feldmann;M. Ijaz;B. Viguier;D. Poquillon;Y. Bouar;A. Ruffini;A. Finel
研究了CMSX-4镍基高温合金单晶在1288 °C下的蠕变行为，该温度是工业上应用于该高温合金的热等静压处理温度。结果发现，在该超固溶温度下，没有γ′-强化发生，高温合金非常软，并且在4和16 MPa之间的应力下快速变形。发现抗蠕变性是非常各向异性的，例如，[001]晶体的蠕变速率比[111]晶体的蠕变速率高约11倍。不同取向的试样也表现出非常不同的颈缩行为。[001]晶体的横截面积的减小达到接近100%，而[111]晶体的横截面积的减小为62%。变形试样的EBSD分析表明，尽管有如此大的局部应变，[001]晶体没有再结晶，而变形较小的[111]晶体在颈缩区内完全再结晶。再结晶程度与变形行为以及高温保压时间有关。从所获得的结果（蠕变各向异性，蠕变速率的应力依赖性，剪切变形的痕迹，和TEM观察）的分析，得出的结论是，主要的应变贡献导致<>{111}八面体滑移。
The creep behavior of single crystals of the nickel-based superalloy CMSX-4 was investigated at 1288 °C, which is the temperature of the hot isostatic pressing treatment applied to this superalloy in the industry. It was found that at this super-solvus temperature, where noγ′-strengthening occurs, the superalloy is very soft and rapidly deforms under stresses between 4 and 16 MPa. The creep resistance was found to be very anisotropic,e.g., the creep rate of [001] crystals was about 11 times higher than that of a [111] crystal. The specimens of different orientations also showed a very different necking behavior. The reduction of the cross-sectional areaψof [001] crystals reached nearly 100 pct, while for a [111] crystalψ= 62 pct. The EBSD analysis of deformed specimens showed that despite such a large local strain the [001] crystals did not recrystallize, while a less deformed [111] crystal totally recrystallized within the necking zone. The recrystallization degree was found to be correlated with deformation behavior as well as with dwell time at high temperature. From the analysis of the obtained results (creep anisotropy, stress dependence of the creep rate, traces of shear deformation, and TEM observations), it was concluded that the main strain contribution resulted from <>{111} octahedral slip.