基于缺陷诱导析出行为的铁基合金辐照损伤自修复机理研究

As the key material of the nuclear reactors, the service stability and lifetime of the Fe-based alloys under extreme conditions such as high temperatures, high pressures, strong irradiation and corrosion play a vital role in the safe and efficient operation of the nuclear power plants. Radiation damage occurs in the Fe-based alloys under irradiation, which gives rise to a series of structural defects, resulting in the radiation hardening, embrittlement and swelling in the materials. Those phenomena result in the performance degeneration, causing the material failure. This project provides a new mechanism to improve the radiation resistance of the steels by the self healing of the radiation damage. Fe-Cr, Fe-Mo and Fe-Au alloys will be studied in the project. The precipitation behavior of the self-healing agent candidate elements will be investigated by the microstructure analysis. The study will focus on the mechanism and effect factors of the defect-induced precipitation, combined with the first principle calculation, in order to unravel the self-healing mechanism of the radiation damage. The self-healing kinetics will be clarified by the study on the kinetics of the precipitation and defects evolution with the increase of the radiation time at 550 ℃. The radiation hardening effect is to be studied by nanoindentation. Meanwhile, the radiation swelling of those three alloys will be analyzed in order to investigate the influence of the self-healing behavior on the radiation resistance. The project is of great significance for developing new long lifetime steel materials with self-healing properties in the application of the advanced reactors.

作为核反应堆的关键材料，铁基合金在高温、高压、强辐照、腐蚀等极端条件下的服役稳定性和使用寿命对核电站的安全高效运行起着至关重要的作用。在辐照条件下，铁基合金会发生辐照损伤，形成一系列的结构缺陷，产生辐照硬化、脆化和肿胀等现象，导致材料使役性能退化，引起材料失效。本项目提出通过辐照损伤的自修复行为提高材料抗辐照性能的新机制。项目以Fe-Cr、Fe-Mo和Fe-Au为研究对象，通过微观结构分析，揭示自修复剂候选元素在高温辐照条件下的析出规律。结合第一性原理计算重点探讨缺陷诱导析出行为的机制和影响因素，揭示辐照损伤的自修复机理。通过研究在550℃随着辐照时间的增加沉淀析出和缺陷演化的动力学过程揭示自修复动力学过程。通过纳米压痕技术研究材料的辐照硬化效应，分析三种合金的辐照肿胀现象，探究自修复行为对材料抗辐照性能的影响。该项目对开发具有自修复性能的长使用寿命先进反应堆用新型钢铁材料具有重要意义。

铁基合金作为第四代裂变反应堆和聚变堆等先进反应堆用结构材料的重要候选材料，在高温、强辐照等苛刻服役条件下的抗辐照性能和使用寿命成为决定其应用潜力的关键因素。开发具有损伤自修复性能的长使用寿命先进反应堆用新型钢铁对核电新型能源发展的安全性、可靠性、经济性具有重要意义。本项目开发出了通过辐照损伤自修复行为提高材料抗辐照性能的新机制。项目系统研究了在室温、高温条件下不同离子辐照类型（氢离子、氦离子、铁离子）辐照引起的铁基合金辐照损伤行为，探究了固溶态合金原子Cr，Au，Cu，Mo，W作为自修复剂候选元素与空位团簇、氦泡、位错等辐照损伤的相互作用。借助慢正电子湮没谱学技术、高分辨透射电子显微镜以及第一性原理计算方法揭示了自修复机理，探究了时效过程中的自修复动力学过程，通过微观定量分析和纳米压痕技术评估了自修复机理对辐照肿胀和辐照硬化效应的影响。研究发现与合金元素Cu相比，合金元素Au具有在辐照损伤位置选择性扩散、偏聚、析出的行为，从而实现辐照损伤的自动愈合。第一性原理计算表明合金元素与微观缺陷（如空位团簇）的结合能是自修复剂选取的关键参数。在Fe-Cr合金中预先形变引入的位错可以大量捕获He原子，降低因辐照级联碰撞产生的辐照损伤，进而降低辐照肿胀。进一步地，在Fe基二元合金中添加Mo或者W，分析了在室温辐照后时效过程中Laves相对开体积缺陷填充修复行为及损伤修复动力学机制。抗辐照性能研究结果显示自修复机理可有效抑制辐照肿胀现象，比如相同辐照条件下，具有自修复效应的Fe-Au合金的辐照肿胀率（0.35%）与Fe-Cu合金（0.51%）相比有明显降低。另外，自修复机制可显著影响铁基合金的辐照硬化效应。在该国家自然科学基金的资助下，项目团队在Applied Surface Science、Journal of alloys and compounds等学术期刊上发表SCI论文6篇；授权国家发明专利1项。