稀土镁合金界面偏聚及界面稳定性的原子尺度研究

Interfacial segregation in magnesium alloys plays a decisive role in determining their mechanical properties. The atomic configuration and stability of the interfacial segregation and the resultant effects on mechanical performance have received intense resurgence in scientific research as the wide use of aberration-corrected transmission electron microscopy (TEM). In this proposal, we will aim at characterizing the interfacial segregation in magnesium-rare earth (RE) alloys at the atomic level, including the atomic configuration and chemical features of grain boundaries, twin boundaries, and kink boundaries, via the aberration-corrected scanning transmission electron microscopy (STEM). We will carry out the in-situ TEM to evaluate the stability and evolution mechanism of specific interfacial segregation, further uncover their corresponding significant effects on mechanical properties of the Mg-RE alloy. The critical factors of interfacial segregation that dramatically affect the mechanical performance of magnesium alloys, such as distinguished solute atoms, special atomic configuration, the volume of segregated atoms, and deformation process, will be unraveled. By directly visualizing atomic configuration and stability of interfacial segregation, combined the mechanical properties, we expect to establish the intrinsic relationship between the solute atoms, features of interfacial segregation, and mechanical properties of the magnesium alloys. The project will shed new light on understanding the novel interfacial segregation behavior of magnesium alloys, and it will also provide a mechanism-driven approach to design interfaces and tailor the mechanical performance of magnesium alloys.

镁合金中界面偏聚对合金的力学性能具有至关重要的影响。具有亚埃尺度空间分辨能力的球差矫正透射电子显微术为在原子尺度下直接观测镁合金中的界面偏聚特征提供了可能。本项目拟以含稀土元素镁合金为主要研究对象，以界面偏聚的原子尺度显微结构及其稳定性为主要研究内容，运用球差矫正透射电子显微术研究晶界偏聚、孪晶界偏聚以及扭折界面偏聚的原子构型；利用外场作用下的原位电子显微技术并结合界面热力学、第一原理模拟等理论分析，阐释上述界面偏聚的稳定性及演化规律，同时分析特征界面偏聚对力学性能的影响，从而建立镁合金中溶质元素，界面偏聚特征和界面稳定性，及其对力学行为影响之间的关联。项目的完成不仅有助于系统理解镁合金中界面偏聚的微观结构特征及稳定性，更为基于界面调控探索高性能镁合金提供原子尺度的结构数据。

界面偏聚是提高材料界面稳定性的重要方式之一，对合金的力学性能及使役行为具有重要影响。对界面偏聚特征的原子尺度认识及界面稳定性的深入理解，是设计界面以提高材料性能的关键。开发优异性能的稀土镁合金被认为是该领域的重要研究方向之一，而其界面结构特征和稳定性及其结构演化规律是亟需解决的基础科学问题。本项目以含稀土元素镁合金为主要研究对象，以特征界面的原子尺度显微结构及其稳定性为主要研究内容，以具有亚埃尺度空间分辨率的球差校正透射电子显微术为主要方法，解析了晶界、孪晶界、扭折界面等界面偏聚的原子构型和化学成分等特征，阐明了不同界面结构的形成机理，探讨了基于界面偏聚强韧化镁合金的微观机理；澄清了长周期有序堆垛（LPSO）结构与基体的界面结构及其稳定性，结合弹性力学分析，提出了位错与溶质元素的协同主导机制；运用原位外场实验，直观揭示了晶界、LPSO结构界面及孪晶界等的热稳定性及演化规律，提出了基于调幅分解的晶界和LPSO结构界面协同生长机理。目前，相关研究成果已经整理总结，发表国际学术期刊论文10余篇，参加国内外学术会议10余次。该项目的研究成果不仅有助于从原子尺度系统理解镁合金中界面微观结构特征及稳定性，更为基于界面调控探索高性能镁合金的设计和制备提供理论支撑。