快堆用超细晶HT-UPS奥氏体钢的界面辐照损伤研究

奥氏体不锈钢是目前实验快堆首选堆芯结构材料，在商用快堆中应用关键在于抗辐照肿胀能力的提高。通过在不锈钢基体内均匀析出纳米析出物以及获得纳米尺寸晶粒均能显著提高其抗辐照肿胀能力。而纳米析出物与超细晶晶界对于辐照点缺陷的共同作用的效果与机制理解仍然不足；以大占比界面组织作为辐照缺陷陷阱的肿胀机制也与传统的辐照晶体缺陷为主的肿胀机制有较大的差异。深入理解多种界面组织大占比共存下的肿胀机制对于提升奥氏体不锈钢抗肿胀能力有重要意义。本课题通过对第四代核能候选结构材料HT-UPS钢进行纳米细晶化处理，得到高体密度的超细晶晶界、纳米析出物等微观界面组织。通过对其进行低能离子辐照，结合分析型透射电子显微镜、三维原子探针等表征手段对辐照后界面处的缺陷结构形貌、成分以及组织分布进行分析，深入探索超细晶HT-UPS的界面组织的抗辐照肿胀机理。将对多界面组织大占比共存下材料的辐照损伤机理产生深入的理解。

Austenitic stainless steels are currently the preferred core structure materials for experimental fast-neutron breeder reactors. The key to their application in commercial fast reactors lies in the improvement of radiation swelling resistance. By uniformly precipitating nano-precipitates in the stainless steel matrix and obtaining nano-sized crystal grains, the ability to resist radiation-induced swelling can be significantly improved. However, the joint effect and mechanism of the interactions of nano-precipitates and ultra-fine grain boundaries on irradiation point defects needs to be deeply understood; the radiation swelling mechanism that uses a large proportion of the interface structures as defect sinks is also quite different from the traditional swelling mechanism dominated by irradiation induced crystal defects. In-depth understanding of the swelling mechanism under the coexistence of multiple interface structures taking a large proportion of the defect sinks is of great significance for improving the anti-swelling ability of austenitic stainless steels. In this project, the Gen-IV nuclear energy candidate structural material HT-UPS steel is subjected to nano-refining treatment to obtain high-density ultra-fine grain boundaries, nano-precipitates and other micro-interface structures. Through low-energy ion irradiation, combined with analytical transmission electron microscopy, three-dimensional atom probe and other characterization methods, the defect structure morphology, composition and distribution at the interface structures after irradiation are analyzed, and the swelling resistance mechanism of the interface structures of the ultra-fine crystal HT-UPS is deeply explored. In-depth understanding of the radiation damage mechanism of materials with the coexistence of multi-interface organizations as major defect sinks will be produced.