Characterization of local deformation around hydrides in Zircaloy-4 using conventional and high angular resolution electron backscatter diffraction
Characterization of local deformation around hydrides in Zircaloy-4 using conventional and high angular resolution electron backscatter diffraction
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DOI：
10.1016/j.matchar.2023.112988
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发表时间：
2023-03
影响因子：
4.7
通讯作者：
Ruth M. Birch;J. Douglas;T. B. Britton
中科院分区：
文献类型：
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作者：
Ruth M. Birch;J. Douglas;T. B. Britton
锆合金-4具有良好的机械性能、耐腐蚀性能和较低的热中子吸收截面，被用作水堆的燃料包壳材料。然而，在使用过程中，由于氢的吸收和氢化物的形成，锆合金-4的机械性能会降低。这些氢化物是脆性的，通常会降低材料的强度和韧性，并增加对延迟氢化物开裂（DHC）的敏感性。在这项工作中，制备了含氢化物的大晶粒zircaly -4，然后使用低温离子束抛光，使用等离子体聚焦离子束（pFIB）和宽离子束（BIB）方法进行横截面，以制备非常高质量的平面，而不优先蚀刻氢化物或锆金属（通常金相抛光优先去除氢化物）。然后使用常规和高角分辨率电子背散射衍射（EBSD）分析来探索锆基体和氢化物之间的形貌、变形场和取向关系。收集了四幅图进行分析，其中包括晶界附近的氢化物：(a)氢化物在靠近三重结的两个连接边界上平滑地装饰；(b)氢化物平滑地修饰边界；(c)光滑的界面装饰和突出到颗粒的混合物；(d)细鳞氢化物突出成一个颗粒。这项工作强调了氢化物在锆基体中的不相容与氢化物与基体的取向关系和晶界特征密切相关。这些结果可以帮助我们更好地理解氢化物在裂缝中的作用，以及应力诱导的氢化物重定向和DHC敏感性。
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 often reduce the strength and toughness of materials as well as increase susceptibility to delayed hydride cracking (DHC). In this work, large grain Zircaloy-4 with hydrides was prepared and then cross sectioned using cryo-ion beam polishing, using plasma focused ion beam (pFIB) and broad ion beam (BIB) approaches to enable the preparation of a very high quality flat surface with no preferential etching of either the hydride or zirconium metal (typically metallographic polishing preferentially removes hydrides). Conventional and high angular resolution electron backscatter diffraction (EBSD) analysis were then used to explore morphology, deformation fields, and orientation relationships between the zirconium matrix and hydrides. Four maps were collected for analysis which included hydrides near grain boundaries: (a) where the hydride smoothly decorates across two of the connecting boundaries near a triple junction; (b) where the hydride smoothly decorates the boundary; (c) a mixture of smooth decoration of the interface and protrusion into the grains; (d) fine scale hydride that protrudes into one grain. This work highlights that incompatibility of the hydride within the zirconium matrix is strongly linked to the orientation relationship of the hydride and matrix, and the grain boundary character. These results may enable enhanced understanding of the role of hydrides in fracture as well as stress-induced hydride reorientation and DHC susceptibility.