纳米尺度晶体/非晶复合材料的耐辐照特性研究

High energy particles generated by nuclear reactions can cause high density defects (interstitials, vacancies, dislocation loops and voids etc.) to metals and alloys, resulting in hardening, void swelling and embrittlement. Recently, nanostructured materials (nanograins, nanolayers and nanotwins) has attracted increasing attention due to their efficiency of absorbing radiation induced defects via high density crystalline/crystalline (C/C) interfaces. However, C/C interfaces have limited free volume for defect-capture. Based on the fact that larger free volume exists at crystalline/amorphous (C/A) interfaces, the applicants try to enhance the radiation tolerance of Cu-Nb nanocomposite by introducing abundant C/A interfaces. We have observed that the radiation induced defects in such materials migrated towards interfaces like water welled up in a spring. We have also found the radiation induced softening and overall excellent radiation resistance in the material. This project is to unveil the mechanism of defect evolution in nanocomposite with C/A interfaces, to explore the mechanism of phase stability and to understand the deformation mechanism of radiation induced softening. This project is expected to establish fundamentals of the radiation resistance of nanocomposite with C/A interfaces and to obtain high-quality academic achievements.

在核反应过程中，高能粒子轰击金属材料导致大量缺陷（间隙原子、空位、位错环、孔洞等），造成材料硬化、肿胀和脆化。近年来，具有高密度晶体/晶体界面的纳米结构材料（纳米晶、纳米多层膜、纳米孪晶等）由于可有效吸收辐照缺陷，而引起极大关注。然而，晶体/晶体界面（共格、半共格、非共格）容纳缺陷能力有限。基于晶体/非晶界面具有高容纳缺陷能力，最近，申请者对含有纳米尺度晶体/非晶界面的Cu-Nb复合材料的耐辐照特性进行探索，采用原位辐照观察发现：在辐照过程中，晶体相中缺陷呈“泉涌”状向晶体/非晶相界面迁移并湮灭的独特现象，且复合材料表现辐照软化及良好的耐辐照性能。本项目拟揭示纳米尺度晶体/非晶相复合材料内部辐照缺陷的演变特征与机制，阐明各相辐照稳定性机制，澄清辐照软化的特征与机制，建立纳米尺度晶体/非晶复合材料的耐辐照基本理论，可望获得高水平学术成果。

晶体/非晶界面具有较大自由体积而可能容纳较多辐照缺陷，故晶体/非晶复合材料具有潜在的耐辐照性。项目组对含有纳米尺度晶体/非晶界面的CuNb复合材料进行Kr离子辐照原位透射电镜实验并首次发现异常的缺陷演变现象，提出该异常可能与Cu、Nb原子的协同扩散行为有关；通过非原位辐照实验，初步总结了其在He离子辐照后的硬化/软化规律；并开发了一种原位测量辐照肿胀的新手段。该项目成果可为人们理解晶体/非晶界面与辐照缺陷交互作用及设计低辐照硬化和低辐照脆性的材料提供新思路。项目期间，在Nano Letters、Applied Surface Science、Science and Technology of Advanced Materials等国际有影响力学术期刊发表标注基金号的SCI论文 9篇，在国际学术会议宣读论文3次，申请中国发明专利1项（尚未授权），培养硕士生博士生各一名。