Vacancies play crucial roles in various phase transformation processes in metallic solids, but their diffusion behaviors in the presence of solute elements are less known. In this work, the impacts of substitutional solute atoms on vacancy diffusion in dilute alloys are quantitatively studied. Using Al-Sn alloy system as an illustrative case, the detailed vacancy diffusion behavior under the influence of Sn atoms is revealed by atomistic kinetic Monte Carlo simulations. Accordingly, a physics-based analytic model is derived to quantify the influences of substitutional solute atoms on the vacancy diffusivity in dilute alloys. In the model, the diffusion of vacancy is rigorously treated as a combination of free diffusion within host atoms and co-diffusion together with solute atoms. Based on the vibrational frequency, migration enthalpy and binding energy of solute-vacancy pair obtained from first-principles calculations, the time fraction for a vacancy trapping by solute atoms and the corresponding correlation factor of diffusion are derived. The predicted vacancy diffusivity in the show-case Al-Sn alloys at different temperatures shows a good agreement with the diffusivity data extracted from KMC simulations within the five-frequency model framework. By using the analytical model, the retarding effects of different impurity elements on vacancy diffusion in Al alloys are screened and discussed, which will help to further exploit the influences of different solute atoms on vacancies in solid-state phase transformations in the alloys.

中文翻译：

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重新审视稀合金中溶质捕获影响下的空位扩散行为


空位在金属固体的各种相变过程中起着至关重要的作用，但它们在溶质元素存在下的扩散行为却鲜为人知。在这项工作中，定量研究了取代溶质原子对稀合金中空位扩散的影响。以 Al-Sn 合金系统为例，原子动力学蒙特卡洛模拟揭示了 Sn 原子影响下的详细空位扩散行为。因此，推导出了一个基于物理的解析模型来量化取代溶质原子对稀合金中空位扩散率的影响。在该模型中，空位扩散被严格视为主原子内自由扩散和与溶质原子共扩散的组合。基于第一性原理计算得到的溶质-空位对的振动频率、迁移焓和结合能，推导出溶质原子俘获空位的时间分数和相应的扩散相关因子。展示案例 Al-Sn 合金在不同温度下的预测空位扩散率与五频模型框架内从 KMC 模拟中提取的扩散率数据具有良好的一致性。通过使用解析模型，筛选和讨论了不同杂质元素对铝合金空位扩散的延迟效应，这将有助于进一步利用不同溶质原子对合金固相相变空位的影响。