Hydrogen embrittlement in Zr-alloy fuel cladding is a primary safety concern for water-based nuclear reactors. Here we investigated the stabilization of planar defects within the forming hydrides by Sn, the primary alloying element of Zircaloy-4 used in the cladding. In order to explain the formation of hydrides and planar defects observed in our experiments, we performed atomic-scale ab initio calculations focusing on the solute interactions with generalized stacking faults in hcp $\alpha$-Zr and fcc zirconium hydrides. Our calculations showed that an increase in Sn concentration leads to a stabilization of stacking faults in both the $\alpha$-Zr and hydride phases. However, the solution enthalpy of Sn is lower in the $\alpha$-Zr as compared to the other hydride phases, indicative of two competing processes of Sn depletion/enrichment at the Zr hydride/matrix interface. This is corroborated by experimental findings, where Sn is less soluble in hydrides and is mostly found trapped at interfaces and planar defects, indicative of stacking faults inside the hydride phases. Our systematic investigation enables us to understand the presence and distribution of solutes in the hydride phases, which provides a deeper insight into the microstructural evolution of such alloy's properties during its service lifetime.

中文翻译：

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Sn对锆及其氢化物堆垛层错能的影响

锆合金燃料包壳中的氢脆是水基核反应堆的主要安全问题。在这里，我们研究了 Sn（包层中使用的 Zircloy-4 的主要合金元素）对形成氢化物内平面缺陷的稳定作用。为了解释实验中观察到的氢化物和平面缺陷的形成，我们进行了原子尺度的从头计算，重点关注溶质与 hcp 中广义堆垛层错的相互作用$\alpha$-Zr 和 fcc 氢化锆。我们的计算表明，Sn 浓度的增加会导致堆垛层错的稳定$\alpha$-Zr和氢化物相。然而，Sn 的溶解焓较低。$\alpha$-Zr 与其他氢化物相相比，表明 Zr 氢化物/基体界面处存在 Sn 贫化/富集的两个竞争过程。实验结果证实了这一点，其中锡在氢化物中的溶解度较低，并且大多数被发现被困在界面和平面缺陷处，表明氢化物相内存在堆垛层错。我们的系统研究使我们能够了解氢化物相中溶质的存在和分布，从而更深入地了解此类合金在其使用寿命期间性能的微观结构演变。