孪晶界溶质偏聚影响孪晶界面迁移和宏观力学行为的机制研究

Interface plays a critical role in plastic deformation and mechanical properties of metals. Controlling the twin boundaries (TBs) is becoming an effective way to tailor deformation behavior and performance of Mg alloys. A recent publication in Science demonstrates that solute atoms can also segregate at coherent TBs in Mg alloys. However, several important scientific problems need a systematical investigation. In the present application, several important issues related to TBs containing solute atoms are systematically studied combing the usage of in-situ experiment techniques and many advanced microstructure characterization methods. Those issues include the influence of solute segregation on TBs migration, the influence of solute atom radius and charge density on the pinning effect on TB migration and the effect of solute segregation at TBs on deformation behavior and twin thermal stability. The aim of this projects involves disclosing the migration mechanism of TBs with solute atoms, finding out the main parameters of solute that determine the pinning effect on TBs, and the mechanism of solute segregation at TBs affecting deformation behavior. At last, a strengthening mechanism based on solute atoms segregation at TBs is developed. The results from this project contribute to the development of TB migration theory and the usage of TBs to tailor microstructure, deformation and mechanical properties of Mg alloys.

界面对金属的塑性成形和力学性能起着至关重要的作用，控制孪晶界面结构已成为调控镁合金塑性加工和使用性能的有效手段。最近在Science的研究报道表明，溶质原子也可在镁合金中的共格孪晶界偏聚，然而与其有关的多个关键科学问题尚需系统研究。本申请以镁合金中含有溶质原子的拉伸孪晶界面为研究对象，综合利用原位试验技术和多种先进的显微分析手段，系统研究溶质在孪晶界偏聚如何影响孪晶界面运动机制、溶质的原子半径和电荷密度对钉扎孪晶界作用的影响、孪晶界溶质偏聚对不同加载路径下的变形行为及孪晶热稳定性的影响，揭示含有溶质原子孪晶界面运动的微观机制，明确对溶质钉扎孪晶界效果起主导作用的原子特征参数，揭示溶质在孪晶界偏聚影响宏观变形行为的微观机制，发展基于孪晶界面溶质偏聚的强化模型。通过本项目的研究丰富和发展孪晶界面运动的理论体系，为利用含有溶质的孪晶界面调控镁合金的组织、塑性变形和力学性能提供重要的理论指导。

本项目以镁合金中含有溶质原子的拉伸孪晶界面为研究对象，综合利用多种先进的微观结构分析手段，开展以下几个方面的研究工作：（1）含有溶质原子孪晶界面运动机制；（2）溶质原子特征对钉扎孪晶界面迁移作用的影响；（3）孪晶界溶质偏聚影响宏观变形行为；（3）不同溶质元素对孪晶热稳定性的影响。.本项目的重要进展包括：（1）从试验上证实了溶质原子偏聚在孪晶界后，孪晶界迁移时溶质原子不跟随孪晶界一起迁移这一悬疑，阐明了含有溶质原子孪晶界的运动机制;（2）定量地阐明了溶质原子的半径和电荷密度对钉扎孪晶界作用的规律，研究表明这两个原子特征参数几乎不影响其钉扎孪晶界迁移的力的大小；（3）发现溶质原子对退孪生时孪晶界面运动的钉扎作用大于对孪晶生长情况的孪晶界面运动；（4）溶质原子半径对孪晶的热稳定性有较大影响，研究结果表明，与小原子半径的Zn和Al相比，大原子半径的Gd和Y元素更有利于提高孪晶的热稳定性。. 本项目发表SCI论文17篇，包括Acta Materialia2篇，培养了博士2名，硕士4名，在本领域重要学术会议做特邀报告5次。