Interfacial Dislocation Networks and Creep in Directional Coarsened Ru-Containing Nickel-Base Single-Crystal Superalloys
Interfacial Dislocation Networks and Creep in Directional Coarsened Ru-Containing Nickel-Base Single-Crystal Superalloys
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DOI：
10.1007/s11661-008-9520-7
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发表时间：
2008-04
期刊：
影响因子：
--
通讯作者：
L. Carroll;Q. Feng;T. Pollock
中科院分区：
文献类型：
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作者：
L. Carroll;Q. Feng;T. Pollock
在γ-γ′晶格失配和相组成变化较大的合金中，研究了定向粗化条件下镍基高温合金单晶蠕变的机理。在无外部施加应力的长期退火实验中建立的界面位错间距表明，实验合金的高温晶格失配范围从接近零到高达- 0.65%。失配的变化影响了950℃和290 MPa蠕变过程中应力诱导的定向粗化（漂移）行为。在蠕变后变形的材料中，γ-γ′界面上的过量位错密度（定义为超出缓解晶格失配所需的位错）随合金成分的不同而变化，最抗蠕变的合金含有最高的过量界面位错密度。在定向粗化蠕变过程中，持续的变形需要对γ′木筏进行剪切，并受到析出相抗剪切能力和界面位错结构的强烈影响。建立了漂流状态下蠕变的初步模型。
Mechanisms of creep deformation in nickel-base superalloy single crystals in the directional coarsening regime have been studied in alloys with large variations inγ-γ′ lattice misfit and phase composition, achieved by Ru additions and variable levels of Cr and Co. Interfacial dislocation spacings established by long-term annealing experiments under no externally applied stress indicate that the experimental alloys have high-temperature lattice misfits ranging from near-zero to as large as −0.65 pct. Variation in misfit influences the stress-induced directional coarsening (rafting) behavior during creep deformation at 950 °C and 290 MPa. In postcreep deformed material, the density of excess dislocations (defined as the dislocations beyond those necessary to relieve the lattice misfit) at theγ-γ′ interfaces varied with alloy composition, with the most creep-resistant alloy containing the highest excess interfacial dislocation density. In the directional coarsening creep regime, continued deformation requires shearing of theγ′ rafts and is strongly influenced by the resistance of the precipitates to shearing as well as the interfacial dislocation structure. A preliminary model for creep in the rafting regime is developed.