密排六方结构材料孪晶对（twin pairs）现象微观机理研究

由于孪晶对（twin pairs，TP）结构的特殊性及其在协调晶间应力集中的作用，HCP材料中的TP现象成为近年来的研究热点。本项目针对HCP材料TP形成过程、控制准则及其对材料性能影响方面研究存在的不足，采用背散射电子衍射技术和数字图像相关方法，结合实验与理论计算建立晶体局部应力模型，通过原位/半原位拉压、加卸载试验和纳米CT等测试手段，阐明HCP结构材料中TP形成过程及不同孪晶变体TP形成过程中的交互作用、澄清TP形核规律与控制准则、揭示材料失效过程中TP与位错及裂纹等缺陷的交互作用，以及TP对材料性能的影响等关键科学问题。本研究将为理解HCP结构材料中的TP现象提供可靠的理论基础和创新性的研究方法，在深入理解TP形核机制及其对材料力学行为影响的基础上，实现可控制备特定TP结构材料的目标，为制备高强韧材料提供可靠的理论与实验指导，对进一步推动HCP结构金属在工程领域的应用具有重要意义。

In recent years, twins pairs (TP) in HCP structured materials have become a hotspot due to their special microstructures and the effect of TP on strain accommodation between neighboring grains. The project aims to analyze and investigate the formation mechanism, control criterion and its influence on mechanical properties of TP in HCP structured materials. Influence of twinning and slip on the formation and selection of TP, along with the formation control criterion of TP will be studied by using electron backscatter diffraction and digital image correlation, as well as grain local stress modeling with experiment results and theoretical calculation. Moreover, the interaction of TP and defects during the failure of materials and the effect on mechanical properties will be investigated by using in-situ and semi in-situ tension and compression test. This project will provide reliable research theory and innovative research method for the investigation of TP in HCP structured materials. Based on the understanding of TP formation mechanism and its effect on mechanical properties, materials with desired TP structures will be designed and prepared. Successful completion of the project will expand our knowledge about deformation twinning in HCP structured materials and provide reliable data for designing HCP structured materials with commercial importance.