铀基非晶合金结构不均匀性及其与塑性变形关联的计算模拟研究

Uranium-based amorphous alloys are a new generation of metallic materials that exhibit significant application prospects in national defense science and technology industry. The intrinsic characteristics of uranium such as the heavy atom effect and localized-itinerant transition of 5f electrons have distinguished uranium-based amorphous alloys from conventional amorphous alloy systems, giving rise to rich scientific issues on the structure-property relationship. However, due to the absence of theoretical research, understanding of key scientific issues in terms of the atomic-scale structure and plastic deformation mechanism of uranium-based amorphous alloys is not sufficient, to some extent hindering the development and application of this new class of amorphous alloys. The project intends to tackle these obstacles by employing multi-scale computation and simulation including ab initio assisted construction of interatomic potential, molecular dynamics and reverse Monte Carlo simulation. Structural characteristics under different scales and their heterogeneity will be revealed for uranium-based amorphous alloys, based on which the plastic rheological behaviors will be further studied. Microscopic mechanism of shear band formation and propagation as well as its correlation with the structural heterogeneity will be clarified, thereby establishing the physical picture of structure and deformation of uranium-based amorphous alloys. This study can facilitate the atomic-level understanding of structural characteristics and plastic deformation mechanism of uranium-based amorphous alloys, establishing a theoretical foundation for the regulation of properties and acceleration of development for this new class of amorphous alloys.

铀基非晶合金是国防科技工业中具有重要应用前景的新一代金属材料，其内禀特殊性如铀的重原子和5f电子局域-巡游特性等明显区别于常规非晶体系，在结构和性能及其关联等基础科学问题上存在丰富的议题。然而，由于铀基非晶合金理论研究的缺失，对其原子尺度结构和塑性变形机制等关键科学问题的认识尚不充分，一定程度上阻碍了铀基非晶合金的研发和工程化应用。本项目拟采用第一性原理计算辅助构建原子间相互作用势、分子动力学模拟和逆蒙特卡罗模拟等多尺度计算模拟方法，系统阐释铀基非晶合金不同尺度下的结构特征及其不均匀性，并在此基础上研究铀基非晶合金的塑性流变行为，阐释剪切带形成和扩展的微观机制并揭示其与结构不均匀性的关联，建立铀基非晶合金结构和形变的物理图像。研究结果有助于从原子水平深入理解铀基非晶合金的结构特征和塑性变形机制，为今后调控铀基非晶合金的性能、加速新型铀基非晶合金的研发进程等提供理论依据。

铀基非晶合金是核工业和军事领域应用潜力很高的一类新型材料，但受限于金属铀的放射性和军事用途，其结构和塑性变形的物理图像尚不明晰。本项目基于计算模拟和理论分析，并引入了结构表象和机器学习等最新的研究方法，揭示了铀基非晶合金和多种常规非晶合金的多层次结构特征，并借助机器学习实现了基于结构有效预测原子在塑性变形或热激活下的响应。.主要取得了如下重要进展：.1、提出了一套基于非晶合金间隙分布的新型结构描述因子，该描述因子对局域环境表现出很强的描述能力，且具有良好的可解释性。利用该描述因子对铀基非晶合金和多种常规非晶合金的短程及中程结构序进行了辨析。.2、设计了先进的机器学习框架，可基于非晶合金静态结构，有效预测其原子在塑性变形或热激活下的非均匀响应。该框架在不同合金成分和体系下保持稳健，并具有极强的泛化能力。借助该框架预测了铀基非晶合金原子尺度的变形倾向性。.项目研究结果在铀基非晶合金和多种常规非晶合金中均得到了检验，加深了对于非晶合金结构-性能关联等基础科学问题的理解，并为调控非晶合金的性能、加速新型非晶合金的研发进程等提供了一定的理论依据。相关研究成果以第一作者兼共同通讯作者发表在Nature Communications和npj Computational Materials。