Due to their remarkable mechanical and chemical properties, Ti-Al based materials are attracting considerable interest in numerous fields of engineering, such as automotive, aerospace, and defense. With their low density, high strength, and resistance to corrosion and oxidation, these intermetallic alloys and compound metal-metallic composites have found diverse applications. The present study delves into the interfacial dynamics of these Ti-Al systems, particularly focusing on the behavior of Ti and Al atoms in the presence of TiAl$_3$ grain boundaries under experimental heat treatment conditions. Using a combination of Molecular Dynamics and Markov State Model analyses, we scrutinize the kinetic processes involved in the formation of TiAl$_3$. The Molecular Dynamics simulation indicates that at the early stage of heat treatment, the predominating process is the diffusion of Al atoms towards the Ti surface through the TiAl$_3$ grain boundaries. The Markov State Modeling identifies three distinct dynamic states of Al atoms within the Ti/Al mixture that forms during the process, each exhibiting a unique spatial distribution. Using transition timescales as a qualitative measure of the rapidness of the dynamics, it is observed that the Al dynamics is significantly less rapid near the Ti surface compared to the Al surface. Put together, the results offer a comprehensive understanding of the interfacial dynamics and reveals a three-stage diffusion mechanism. The process initiates with the premelting of Al, proceeds with the prevalent diffusion of Al atoms towards the Ti surface, and eventually ceases as the Ti concentration within the mixture progressively increases. The insights gained from this study could contribute significantly to the control and optimization of manufacturing processes for these high-performing Ti-Al based materials.

翻译：鉴于钛-铝基材料兼具优异的力学性能和化学稳定性，其在汽车、航空航天及国防等工程领域正引发广泛关注。凭借低密度、高强度、耐腐蚀及抗氧化等特性，这类金属间化合物合金与金属基复合材料已获得多元化应用。本研究深入探究了钛-铝体系的界面动力学行为，特别聚焦于实验热处理条件下TiAl$_3$晶界处Ti与Al原子的迁移规律。通过联合运用分子动力学模拟与马尔可夫状态模型分析，我们系统考察了TiAl$_3$形成过程中的动力学机制。分子动力学模拟表明，热处理初期以Al原子经TiAl$_3$晶界向Ti表面扩散为主导过程。马尔可夫状态模型成功识别出反应生成的Ti/Al混合相中Al原子的三种动态状态，每种状态均呈现独特的空间分布特征。以跃迁时间尺度作为动力学速率的定性指标，研究发现近Ti表面区域的Al原子动力学速率显著低于近Al表面区域。综合结果揭示了完整的三阶段扩散机制：始于Al的预熔化过程，继以Al原子向Ti表面的优势扩散，最终随混合相中Ti浓度递增而逐渐终止。本研究获得的认知可为高性能钛-铝基材料制备工艺的调控与优化提供重要理论支撑。