面心立方单相固溶体高熵合金辐照损伤行为及其机理研究

High entropy alloys have been emerging as a new class of metallic materials over the last decade, and have a great potential to be utilized as next-generation nuclear materials due to their excellent radiation damage resistance. Nevertheless, the mechanism for radiation damage resistance in HEAs is still not clear so far. To address this challenge, this project will systematically investigate irradiation behaviors of HEAs with a single FCC solid solution structure by combining theoretical calculations with experimental studies, and reveal the influences of chemical and topological disorders on the formation and evolution of radiation-induced defects in the HEAs during the radiation process. The effects of chemical and topological disorders on displacement threshold energy, energies for formation and migration of defects, and electron structure will be revealed by first-principle calculations. Moreover, the dynamic process of primary displacements occurred in the HEAs under irradiation will be modeled by molecular dynamic simulations, by which the influences of chemical and topological disorders on cascade collision, and the formation and evolution of defects will be scrutinized. The fine structures of these alloys before and after irradiation will be characterized comprehensively by the state-of-the-art experimental techniques, such as high resolution transmission electron microscopy, three dimension atom probe, and synchrotron X-ray scattering. Eventually, we will elucidate the mechanism for radiation damage resistance of HEAs and establish the scientific relationship between the intrinsic physical properties and radiation damage behavior for these highly concentrated alloys. The implement of the proposed research will not only reveal the nature of radiation damage in HEAs at the electron scale, but also provide a theoretical guideline for designing novel HEAs with superior radiation damage resistance.

高熵合金是最近发展起来的一类新型金属材料。研究表明，高熵合金具有优异的抗辐照性能，有望成为新一代核反应堆内结构材料，但目前对高熵合金的辐照损伤机理缺乏认知。为此，本项目拟采用理论计算与实验研究相结合的方法，对面心立方单相固溶体高熵合金的辐照损伤行为进行系统研究，揭示化学无序性（组元数）与拓扑无序性（晶格畸变）对高熵合金辐照过程中缺陷形成和演化行为的影响规律。通过第一性原理计算明确组元数和晶格畸变对合金离位阈能、缺陷特征能、电子结构等基本物性的影响规律；通过分子动力学模拟辐照下合金中发生的初级离位损伤过程，厘清组元数和晶格畸变对级联碰撞、缺陷的产生与演化行为的影响规律；通过高分辨透射电镜、三维原子探针、同步辐射等先进技术系统表征合金辐照前后的微观精细结构。项目的开展将从电子尺度上揭示高熵合金辐照损伤的物理本质，建立高熵合金本征物性与辐照性能之间的科学关系，为研发新型高性能核材料提供理论指导。

本项目针对高熵合金在辐照损伤行为与机理相关的基本科学问题，采用理论计算与实验研究相结合的方法，对典型面心立方高熵合金的缺陷特征能、化学短程序及其对辐照损伤性能的作用规律进行了系统研究，在以下几个方面取得了重要进展：（1）获得了构型熵和化学成分对Fe-Co-Ni-Cr-Mn系面心立方高熵合金层错能的影响规律；（2）揭示了纳米析出强化高熵合金具有优异抗辐照性能的起源；（3）从原子尺度上获得了面心立方高熵合金辐照缺陷的形成及其动态演化规律；阐明了构型熵和化学短程序对高熵合金辐照性能的作用规律；（4）研发出有望作为新型抗辐照材料的有序间隙氧团簇强韧化难熔高熵合金和氧化物弥散强化（ODS）高熵合金。截止目前，项目资助的相关研究成果在《Nature》、《Advanced Materials》、《Materials Today》、《Science Advance》等国际期刊上发表学术论文40篇；参加国内外会议21人次，其中邀请报告14人次；获得国家发明专利5件；培养博士生4人，硕士生4人。项目负责人获2018年教育部自然科学一等奖1项（高熵合金的相形成规律及组织性能研究）。项目的开展不仅为理解高熵合金的辐照损伤机制奠定了基础，而且为设计高性能抗辐照多主元合金提供了理论依据。