The microstructure and microtexture of zirconium oxide films studied by transmission electron backscatter diffraction and automated crystal orientation mapping with transmission electron microscopy
The microstructure and microtexture of zirconium oxide films studied by transmission electron backscatter diffraction and automated crystal orientation mapping with transmission electron microscopy
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DOI：
10.1016/j.actamat.2014.07.062
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发表时间：
2014-11-01
期刊：
影响因子：
9.4
通讯作者：
Preuss, M.
中科院分区：
文献类型：
--
作者：
Garner, A.;Gholinia, A.;Preuss, M.
通过两种新型的，超高的空间分辨率谷物映射技术，即自动晶体方向定向，对核级锆合金水性腐蚀过程中形成的纳米结构薄氧化物膜的详细表征已进行了透射电子显微镜（TEM）和透射电子反向衍射（T-EBSD）中的映射。尽管前者提供了出色的空间分辨率，并能够识别四方ZRO2晶粒与5 nm一样小，但具有T-EBSD的上角分辨率和明确的索引，可以验证TEM观测值。两种技术都表明，在无应力的条件下（通过聚焦离子束铣削制备的TEM箔），氧化物主要由良好的圆柱单斜粒晶粒组成，其转化很高，这表明从四方到单斜晶的转化， ZRO2是一个连续的过程，并且柱状晶粒的很大一部分从与金属氧化物界面平行的（0 0 1）平面相似的压力稳定的四方晶粒转化。 TEM分析还表明，整个氧化物中的尺寸稳定，等亚四方晶粒的一小部分。发现这些谷物从预期的（0 0 1）生长方向上显示出严重的未对准，这解释了这些谷物的生长有限。在提供有关锆合金腐蚀机制的新见解的背景下讨论了这些观察结果，这对于改善水冷反应堆中使用的燃料组件的使用寿命非常重要。 （c）2014 Acta Mitalietia Inc.由Elsevier Ltd出版。这是CC根据许可（http://creativecommons.org/licenses/by/3.0/）的开放访问文章。
A detailed characterization of nanostructured thin zirconium oxide films formed during aqueous corrosion of a nuclear-grade zirconium alloy (Zircaloy-4) has been carried out by means of two novel, ultra-high-spatial-resolution grain mapping techniques, namely automated crystal orientation mapping in the transmission electron microscope (TEM) and transmission electron backscatter diffraction (t-EBSD). While the former provided excellent spatial resolution with the ability to identify tetragonal ZrO2 grains as small as similar to 5 nm, the superior angular resolution and unambiguous indexing with t-EBSD enabled verification of the TEM observations. Both techniques revealed that in a stress-free condition (TEM foil prepared by focused ion beam milling), the oxide consists mainly of well-oriented columnar monoclinic grains with a high fraction of transformation twin boundaries, which indicates that the transformation from tetragonal to monoclinic ZrO2 is a continuous process, and that a significant fraction of the columnar grains transformed from stress-stabilized tetragonal grains with (0 0 1) planes parallel to the metal-oxide interface. The TEM analysis also revealed a small fraction of size-stabilized, equiaxed tetragonal grains throughout the oxide. Those grains were found to show significant misalignment from the expected (0 0 1) growth direction, which explains the limited growth of those grains. The observations are discussed in the context of providing new insights into corrosion mechanisms of zirconium alloys, which is of particular importance for improving service life of fuel assemblies used in water-cooled reactors. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).