High-resolution electron microscopy of dislocation ribbons in a CMSX-4 superalloy single crystal
High-resolution electron microscopy of dislocation ribbons in a CMSX-4 superalloy single crystal
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DOI：
10.1016/j.actamat.2012.05.014
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发表时间：
2012-07-01
期刊：
影响因子：
9.4
通讯作者：
Rae, C. M. F.
中科院分区：
文献类型：
--
作者：
Vorontsov, V. A.;Kovarik, L.;Rae, C. M. F.
高分辨率扫描透射电子显微镜（STEM）已被用于研究单晶高温合金样品中的位错结构，这些样品已受到有利于初级蠕变制度的条件的影响。研究揭示了蠕变过程中剪切γ′析出相时扩展的a/2 < 1 1 2 >位错的详细结构。这些位错解离的方式与使用位错相场模型的预测一致，也表明了在其运动过程中重新排序过程的重要性。a < 1 1 2 >位错所做的剪切也被发现扭曲了γ / γ′界面，将其外观从线性变为“锯齿”模式。另一个重要的观察结果是具有高原子质量的合金元素在层错上的偏析，可能是为了在剪切过程中降低它们的能量。在高温合金的γ通道中还观察到大量的a/2 < 1 1 0 >解离位错。STEM成像提供的高分辨率使人们能够研究常规弱束流TEM通常难以观察到的高能断层，如γ′中的复杂本征和外征层错以及γ′中的本征层错，并对其能量进行估计。(C) 2012材料学报Elsevier Ltd.出版。版权所有。
High-resolution scanning transmission electron microscopy (STEM) has been used to study the structure of dislocations in single crystal superalloy samples that have been subjected to conditions that favour the primary creep regime. The study has revealed the detailed structure of extended a/2 < 1 1 2 > dislocations as they shear the gamma' precipitates during creep. These dislocations dissociate in a manner that is consistent with predictions made using the phase-field model of dislocations and also suggests the importance of the reordering process during their movement. The shearing done by the a < 1 1 2 > dislocations was also found to distort the gamma/gamma' interface, changing its appearance from linear to a "saw tooth" pattern. Another important observation was the segregation of alloying elements with a high atomic mass to the stacking faults, presumably to reduce their energies during shear. Numerous a/2 < 1 1 0 > dissociated dislocations were also observed in the gamma channels of the superalloy. The high resolution provided by the STEM imaging enables one to study the high-energy faults that are usually difficult to observe in conventional weak-beam TEM, such as complex intrinsic and extrinsic stacking faults in the gamma' and intrinsic stacking faults in the gamma, and to make estimates of their energies. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.