微量元素对铝添加高铬ODS钢纳米氧化物形成机制的影响

Al-alloyed high-Cr oxide dispersion strengthened (ODS) ferritic steels are the most promising cladding materials for generation IV nuclear fission reactors such as supercritical pressurized water reactor, lead bismuth-cooled fast reactor and sodium-cooled fast reactor. It has been demonstrated that the dispersion morphology of oxides can be improved remarkably and, consequently, the particle strengthening be significantly enhanced, by a minor addition of reactive elements such as Zr and Hf. However, the changes in the phase and morphology of oxides, and the changes in the structure and chemistry of metal/oxide interfaces due to minor element addition and the corresponding underlying mechanisms have not be completely clarified up to now. Moreover, the reason why various orientation relationships coexist between the nano-sized oxides and the ferritic matrix, and the formation mechanisms of nano-sized complex oxides are still not well understood. In this work, the advanced characterization methods, including high resolution transmission electron microscopy (HRTEM) combining with through-focus exitwave function (EW) reconstruction technique, high resolution high angle annular dark field imaging (HR-HAADF) combining with simultaneous atomic scale electron energy loss spectroscopy in scanning transmission electron microscopy mode (STEM-EELS), atomic-scale energy-dispersive X-ray spectroscopy in scanning transmission electron microscopy mode (STEM-EDS) and atomic probe tomography (APT) etc., will to be used to investigate the atomic and nano- mesoscopic scale structure and chemistry of Al-alloyed high-Cr ODS ferritic steels with various minor reactive elements. The crystallographic nature of the coexistence of a variety of morphologies of oxides, and the crystallographic nature of the coexistence of a variety of orientation relationships between the nano-sized complex oxides and the ferritic matrix will be clarified by the accurate determination of the morphology and crystal structure of the oxides, and the orientation relationships between the nanoparticles and matrix. The mechanism of minor-element manipulating the morphology of nano-sized complex oxides and the metal/oxide interfaces in ODS steels, and the formation mechanism of nanometer scale oxides can be revealed via the quantitative characterization of the structures and chemistry of nano-sized complex oxides and metal/oxide interfaces at atomic scale. This project will enrich the theory of manipulating oxide morphology and metal/oxide interfaces in ODS alloys, and provide a theory foundation and additional guidelines on the design and development of new ODS alloys with high performance by micoalloying.

铝添加高铬ODS铁素体钢是第四代核反应堆理想候选包壳材料。研究表明，添加微量元素（Zr和Hf）可显著改善纳米氧化物形貌，增强强化效果。然而，对于微量元素引起的氧化物物相、形貌及金属/氧化物界面结构和化学的改变及其原因、氧化物与基体存在多种取向关系的原因及纳米氧化物形成机制还缺乏充分认识。本项目拟采用HRTEM和系列变焦像出射波函数重构技术、HR-HAADF和原子分辨率STEM-EELS、原子分辨率STEM-EDS及APT等先进表征手段，针对含不同微量元素的ODS钢，通过对纳米氧化物结构、形貌和取向关系的准确确定，揭示其存在多种形貌和取向关系的晶体学本质；通过对纳米氧化物和金属/氧化物界面的结构和化学的原子尺度定量表征，阐明微量元素改变氧化物形貌的机理及纳米氧化物形成机制。本项目研究成果可丰富ODS钢纳米氧化物形貌和界面调控理论，为通过微合金化提高ODS合金性能及开发新型合金提供理论依据。

铝添加高铬ODS铁素体钢是第四代核反应堆理想候选包壳材料。本项目采用HRTEM等先进表征手段，针对含不同微量活性元素（Zr和Hf等）的ODS钢，通过对纳米氧化物结构、形貌和取向关系的准确确定，揭示了其存在多种形貌和取向关系的晶体学本质；通过对纳米氧化物和金属/氧化物界面的结构和化学的原子尺度定量表征，阐明了微量元素改变氧化物形貌的机理及纳米氧化物形成机制。本项目研究成果丰富了ODS钢纳米氧化物形貌和界面调控理论，为通过微合金化提高ODS合金性能及开发新型合金提供理论依据。

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