Ledges and grooves at γ/γ′ interfaces of single crystal superalloys
Ledges and grooves at γ/γ′ interfaces of single crystal superalloys
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DOI：
10.1016/j.actamat.2015.02.005
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发表时间：
2015-05
期刊：
影响因子：
9.4
通讯作者：
A. Parsa;P. Wollgramm;H. Buck;A. Kostka;C. Somsen;A. Dlouhý;G. Eggeler
中科院分区：
文献类型：
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作者：
A. Parsa;P. Wollgramm;H. Buck;A. Kostka;C. Somsen;A. Dlouhý;G. Eggeler
本文研究了单晶镍基高温合金γ/γ′界面上沟槽和台阶（典型尺寸：<100 nm）的形成。我们强调以前的工作，记录存在这样的接口不规则性，并表明它们的数量和大小增加在高温暴露和蠕变。我们利用衍射衬度立体透射电子显微镜（TEM）为热处理和蠕变后γ/γ′界面位错附近的台阶和沟槽的存在提供了新的证据。我们提出了一个二维模型的界面区域，它显示了位错应力场如何改变当地的化学势和驱动扩散通量，导致形成的凹槽。数值研究的结果在相关的时间尺度上产生现实的凹槽尺寸。在本研究中获得的结果表明，凹槽和凸台的形成代表了一个基本的过程，需要考虑合理化的漂流动力学时，γ′相的定向粗化。
In the present work we study the formation of grooves and ledges (typical size: <100 nm) atγ/γ′ interfaces of single crystal Ni-base superalloys. We highlight previous work which documents the presence of such interface irregularities and shows that their number and size increases during high temperature exposure and creep. We use diffraction contrast stereo transmission electron microscopy (TEM) to provide new evidence for the presence of ledges and grooves near dislocations atγ/γ′ interfaces after heat treatment and creep. We present a 2D model of the interfacial region which shows how dislocation stress fields alter local chemical potentials and drive diffusional fluxes which result in the formation of a groove. The results of the numerical study yield realistic groove sizes in relevant time scales. The results obtained in the present study suggest that the formation of grooves and ledges represents an elementary process which needs to be considered when rationalizing the kinetics of rafting, the directional coarsening of theγ′ phase.