AI 中文总结
研究FeCrAl合金中用于耐事故燃料包壳的空位扩散，用物种分辨的KMC模型结合线性替代模型，通过采样不同成分映射局部化学环境对空位跳跃及扩散率的影响，发现增加Cr含量降低扩散率，富Cr合金空位迁移受抑制。
AI 中文摘要
铁铬铝（FeCrAl）合金是轻水反应堆中耐事故燃料包壳的主要候选材料，其优异的高温抗氧化性有望在冷却剂丧失事故中延长应对时间。包壳在反应堆内的寿命最终由辐射诱导的微观结构演变决定，其中点缺陷传输是主要机制，但对此仍知之甚少。在此，我们使用一种物种分辨的动力学蒙特卡罗（KMC）模型来模拟FeCrAl中的空位扩散，该模型由基于通过Hop-Decorate工作流程生成的迁移势垒数据库训练的线性替代模型进行参数化。通过对Fe-Cr-Al系统中从富铁到富铬范围内的成分进行采样，我们绘制了局部化学环境如何控制空位跳跃以及宏观扩散率。我们发现，增加合金中的Cr含量会逐渐降低空位的整体扩散率，尽管激活能保持相对恒定。这意味着合金中的Fe含量越高，空位扩散越快，从而增加与快速移动的间隙原子的湮灭事件，可能减少辐照诱导的缺陷并提高辐射耐受性。相反，我们发现富Cr合金成分的激活能明显升高，扩散明显减慢，在与事故相关的温度下低几个数量级。这表明在辐照下已知会形成的富Crα'相中，空位迁移受到抑制。
英文摘要
Iron-chromium-aluminium (FeCrAl) alloys are leading candidates for accident-tolerant fuel cladding in light-water reactors, where their superior high-temperature oxidation resistance promises to extend coping times during loss-of-coolant accidents. The in-reactor lifetime of cladding is ultimately governed by radiation-induced microstructural evolution of which point defect transport is the dominant mechanism, however, this remains poorly understood. Here, we use a species-resolved kinetic Monte Carlo (KMC) model for vacancy diffusion in FeCrAl, parameterised by linear surrogate models trained on a database of migration barriers generated through the Hop-Decorate workflow. By sampling compositions spanning the Fe-rich to Cr-rich range of the Fe-Cr-Al system, we map how the local chemical environment controls vacancy hopping and hence macroscopic diffusivity. We find that increasing the Cr content in the alloy progressively decreases global diffusivity of vacancies even though activation energies stay relatively constant. This implies that the higher the Fe content in the alloy, the faster vacancies diffuse, thereby increasing annihilation events with fast-moving interstitials, potentially reducing irradiation induced defects and increasing radiation tolerance. Conversely, we find that Cr-rich alloy compositions stand out with a markedly elevated activation energy and significantly slower diffusion, orders of magnitude lower at accident-relevant temperatures. This indicates suppressed vacancy mobility in Cr-rich $α'$ phases which are known to form under irradiation.
