A Conventional and High Resolution Electron Backscatter Diffraction (EBSD) Study of Stress Fields around Hydrides in Zircaloy-4.
A Conventional and High Resolution Electron Backscatter Diffraction (EBSD) Study of Stress Fields around Hydrides in Zircaloy-4.
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Zircaloy-4 中氢化物周围应力场的常规和高分辨率电子背散射衍射 (EBSD) 研究。
DOI：
10.1093/micmic/ozad067.797
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Birch RM
中科院分区：
文献类型：
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作者：
Birch RM
锆-4被用作水反应堆的燃料包壳材料，因为它具有良好的机械性能，耐腐蚀性和低热中子吸收截面。然而，锆-4合金的机械性能在使用过程中会由于氢吸收和氢化物形成而降低。这些金属是脆性的，并且可以降低薄压力管的强度和韧性，这可以影响延迟氢化物开裂，这促使进一步表征。我们使用电子背散射衍射（EBSD）来探索锆基体和锆颗粒之间的形态和取向关系，其中颗粒位于晶界和晶界附近。制备具有氢化物[2]的块状-α锆合金-4 [1]，然后使用氩等离子体聚焦离子束（pFIB）和宽离子束（BIB）方法[3]使用低温离子束抛光进行横截面处理，以能够制备非常高质量的平坦表面，而不会优先蚀刻氢化物或锆金属使用配备有eFlashHD 2检测器的Quanta 650 FEG-SEM进行常规EBSD（图2）和高角分辨率EBSD（HREBSD）捕获衍射图案。传统的EBSD分析是使用在线索引的数据进行的，随后使用MTEX进行后处理。使用XEBSD MATLAB代码进行HREBSD分析，以提取（晶格）应变、晶格旋转和几何必需位错密度的相对变化。收集了四个图用于分析，其包括位于以下区域的晶界：（a）三重结附近，其中氢化物平滑地装饰穿过两个连接的晶界;（B）晶界上，其中氢化物平滑地装饰晶界;（c）晶界处的一对晶界，其包含界面的平滑装饰和向晶粒中的突出的混合物;（d）在突出到一个晶粒中的晶界上沉积。结合常规和HR-EBSD分析突出了锆基质内氢化物的不相容性与氢化物和基质的取向关系以及晶界的性质密切相关。对于光滑装饰界面的区域，通常观察到有限的不相容性（即晶格应变和晶格旋转很小）。与此相反，较大的变化存储变形观察氢化物不适合“以及”在任何一个晶粒。
Zircaloy-4 is used as a fuel cladding material for water reactors, as it has good mechanical properties, corrosion resistance, and a low thermal neutron absorption cross section. However, the mechanical performance of Zircaloy-4 can be reduced during service due to hydrogen uptake and hydride formation. These hydrides are brittle and can reduce the strength and toughness of thin pressure tubes, which can impact delayed hydride cracking, which motivates further characterization. We use electron backscatter diffraction (EBSD) to explore morphology and orientation relationships between zirconium matrix and zirconium hydrides, where the hydrides are located at and near grain boundaries. Blocky-α Zircaloy-4 [1] with hydrides [2] was prepared and then cross sectioned using cryo-ion beam polishing using argon plasma focused ion beam (pFIB) and broad ion beam (BIB) approaches [3] to enable the preparation of a very high quality flat surface with no preferential etching of either the hydride or zirconium metal (Fig. 1).Conventional EBSD (Fig. 2) and high angular resolution EBSD (HREBSD) was performed capturing diffraction patterns using a Quanta 650 FEG-SEM equipped with an eFlashHD2 detector. Conventional EBSD analysis was performed using data that was indexed online, and subsequently post processed using MTEX. HREBSD analysis was performed using the XEBSD MATLAB code to extract relative variations in (lattice) strain, lattice rotation, and the density of geometrically necessary dislocations. Four maps were collected for analysis which included hydrides located in the following regions:(a) near a triple junction, where the hydride smoothly decorates across two of the connecting grain boundaries;(b) on a grain boundary, where the hydride smoothly decorates the grain boundary;(c) a pair of hydrides at a grain boundary which contain a mixture of smooth decoration of the interface and protrusion into the grains;(d) hydrides on a grain boundary which protrude into one grain. The combined conventional and HR-EBSD analysis highlights that incompatibility of the hydride within the zirconium matrix is strongly linked to the orientation relationship of the hydride and matrix, as well as the character of the grain boundary. For regions that smoothly decorate an interface, typically limited incompatibility is observed (ie the lattice strains and lattice rotations are small). In contrast, larger variations in stored deformation are observed where the hydride does not fit ‘as well’in either grain.