Ti晶界原子结构及其变形机制的电子显微学研究

Study of grain boundaries (GBs) in Ti is of significant importance for understanding the behaviors of grain refinement strengthening and alloying strengthening, offering a theoretical basis for improving the mechanical properties of Ti and Ti alloys. Clarifying the direct correlation between the atomic structure and deformation mechanism of GBs is a fundamental scientific issue for materials science, which is still far from being resolved. In this study, the deformation behaviors of Ti GBs will be investigated on the basis of fabricating Ti bi-crystals through a combined study of aberration-corrected transmission electron microscopy (Cs-TEM) and in-situ TEM deformation. The atomic structure and chemical distribution of a series of Ti Σ symmetric tilted GBs and low-angle GBs will be obtained using Cs-TEM. In-situ TEM deformation experiments will be performed to simultaneously obtain the information of GB dynamic evolution and corresponding mechanical properties, paying more attention to the interactions between GBs and dislocations/twins during deformation. Based on the experimental results, first-principles calculations and molecular dynamics simulations will be conducted to reveal the intrinsic mechanisms for the influence of atomic structure on the deformation mechanism of GBs. This study will not only deepen our understanding of the roles of Ti GBs on the materials strengthening but also provide important reference for studies of GBs in other hexagonal metals.

研究Ti的晶界问题对理解其细晶强化与合金强化行为至关重要，可为提高Ti及其合金的力学性能提供重要理论依据。揭示材料晶界原子结构与其变形机制之间的直接关系是材料科学研究中的一个基础科学问题，迄今未得到圆满的解决。本项目拟在Ti双晶样品制备的基础上，主要运用像差校正电子显微术和透射电镜原位变形等研究方法，系统开展有关Ti晶界变形行为的研究工作。通过像差校正电子显微结构表征与成分分析实验确定Ti系列Σ倾转晶界与小角度晶界的原子结构与成分分布；通过透射电镜原位变形实验获得其晶界结构演化的动态信息与相应的力学性能数据，重点关注变形过程中晶界与位错、孪晶的交互作用；基于实验所得结果，结合第一性原理与分子动力学理论计算，揭示Ti晶界的原子结构影响其变形机制的内在机理。本项目的完成不仅可以深化对Ti的晶界在材料强化中所起作用的认识，也可为研究其他六角结构金属材料中的晶界问题提供重要借鉴。

钛是一种过渡族金属元素，在地壳中的储量较为丰富，是应用广泛的结构金属元素之一，研究其变形及氧化行为对材料的设计和应用具有重要的理论指导意义。项目在纯钛材料中展开了原位电子显微学以及原子级电子显微学研究，对比研究纯钛及钛合金的变形中的晶界行为，探索晶界对材料相变以及孪生的影响。此外对纯钛在初期氧化过程中氧的溶解行为进行了研究，首次从实验的角度上证实了这一过程的存在，并在原子尺度上揭示了初级氧化过程中氧原子在金属次表面的占位规律，阐明氧在次表面溶解对后续氧化过程的影响。项目执行期间，共发表SCI论文4篇，在审论文1篇；参加全国电子显微学年会两次，并做邀请报告1次；参与培养研究生3名，毕业生1名并获博士学位；获批辽宁省基金指导计划项目1项。