界面结构对层状金属材料抗辐照性能影响的像差校正电子显微学研究

With the energy and environment issues become progressively worse, green nuclear power has become an inevitable choice in China. Advanced nuclear technology requires more robust structural materials. Promising material candidates are nanolayered metallic composites owing to their interface dominated excellent irradiation tolerance. However, the mechanism of interface effects on irradiation tolerance is unclear. Using aberration-corrected (scanning) transmission electron microscopy (TEM/STEM), the project will investigate the relationship between interface structures and irradiation resistance systematically, based on materials that nanolayered Cu-Nb and Cu-Ag prepared by accumulative roll bonding (ARB) and a flux-melting technique, respectively, both before and after He irradiation. Using aberration-corrected TEM/STEM, we plan to directly observe He bubbles with diameters less than 1nm which can not be characterized via conventional TEM, study atomistic interface features of Cu-Nb and Cu-Ag, and effects of the atomistic interface features on nucleation and growth of He bubbles, as well as variations of the atomistic interface structures after irradiation. In addition, by comparing the different irradiation tolerance between the interfaces, we will establish an intrinsic relationship between the atomistic interface structures and their irradiation resistance, and give insight into designing and developing advanced irradiation tolerant structural materials.

随着能源和环境问题的日益严峻，发展绿色核电是我国的必然选择。先进核电技术对结构材料提出了越来越高的要求。纳米层状复合金属材料因其优异的界面抗辐照效应而具有了很好的应用前景，但其抗辐照的机理尚不清楚。本项目将利用像差校正的透射电子显微学技术对界面结构和抗辐照性能之间的关系进行深入系统的研究。项目拟选取氦（He）辐照前后的由叠轧法制备的Cu-Nb和熔炼法制备的Cu-Ag块体纳米多层材料为研究对象，通过以像差校正的扫描透射电子显微学为主的分析方法，对小于1nm的传统透射电子显微学无法研究的He泡进行直接观察，并研究Cu-Nb和Cu-Ag的原子级界面结构特征，和此界面结构特征对He在界面上的形核和长大的影响，以及在此过程中界面结构本身的演化。最终通过对Cu-Nb和Cu-Ag之间四种不同类型界面的对比研究，建立原子级界面结构特征与材料抗辐照性能之间的内在关系，为研发新一代耐辐照材料提供基础结构信息。

核电是我国十三五期间重点发展的清洁能源。高性能核电材料为核电安全提供保障。异质界面具有优异的抗辐照损伤潜能，因此界面工程是设计下一代高性能核电材料的基本策略之一。本项目通过透射电子显微学的研究建立了原子尺度界面结构、材料辐照损伤缺陷分布以及材料力学性能之间的关系，为通过界面调控材料的抗辐照损伤性能提供了理论基础。主要研究内容及结论：（a）研究了辐照缺陷空洞（void）与Cu-Ag、Cu-Nb界面的交互作用，揭示了Cu-Ag、Cu-Nb界面由于失配位错网的存在具有界面结构和界面能的周期性分布特征，空洞在失配位错网节点处形核并向表面能较低一侧长大；（b）研究了Cu-Nb块体纳米层状材料的层厚、辐照温度、辐照剂量对辐照产生缺陷与Cu-Nb界面交互作用及其对显微硬度的影响，发现辐照缺陷空洞能否跨越界面由界面密度和温度共同决定，同时辐照可以导致材料软化；（c）研究了辐照缺陷层错四面体与Cu-Ag界面的交互作用，揭示了界面诱导的层错四面体形成机制；（d）研究了Cu-Nb多层材料中He泡的迁移规律，揭示了He泡迁移速率的临界尺寸效应。相关结果发表Scientific Reports和Journal of Nuclear Materials各一篇，其余结果正在整理发表中。此外，本项目培养硕士生一名。