成功开发高性能包壳材料是轻水堆抗事故燃料（ATF）产业化的前提和基础。Fe-Cr-Al ODS钢有优异的高温蠕变强度、耐辐照性能和抗腐蚀性能，是ATF最有希望的候选包壳材料之一。目前迫切需要开展通过优化Fe-Cr-Al ODS钢合金成分，以便尽可能改善高温强度与环境相容性，并保证在长期服役条件下不发生热时效脆化。研究发现：ODS钢纳米氧化物显著抑制热时效硬化；热时效Fe-Cr-Al ODS钢中形成了核-壳结构纳米析出物，但相关原因尚未查清。因此，本申请项目系统研究不同合金元素对ATF包壳用Fe-Cr-Al ODS钢的热时效力学行为和相分离机制的影响规律，重点研究核-壳结构纳米析出物形成机制及其与纳米氧化物热时效硬化抑制效应之间的关系与内在联系及其机理，结合考察不同合金元素对纳米氧化物强化效果以及环境相容性的影响，形成合金设计指导原则和提高综合性能的方法，以满足ATF包壳管服役要求。

Successful development of high-performance cladding materials is the prerequisite and foundation of the industrialization of accident tolerant fuel (ATF) of light water reactors. Fe-Cr-Al ODS steel is one the most promising cladding materials of ATF due to the excellent resistance to creep, irradiation and corrosion. At present, it is urgent to optimize the chemical compositions of Fe-Cr-Al ODS steel so as to improve the high temperature strength and the environmental compatibility as much as possible and, at the same time, ensure that there is no thermal aging embrittlement under long-term service conditions. It has been demonstrated that the nanometer-scale oxides significantly inhibits thermal aging hardening of ODS steels and, moreover, core-shell precipitates are formed in Fe-Cr-Al ODS steels after isothermally aged for long time. However, the related reason has not been clarified yet. Therefore, in this proposal, the effects of various kinds of alloy elements on the mechanical behavior of thermal aged Fe-Cr-Al ODS steels and the corresponding mechanisms of Fe-Cr phase separation should be investigated systematically. The emphases are to study the formation mechanism of core-shell precipitates, the underlying reasons why the thermal aging hardening of ODS steels can be considerably suppressed by the nanometer-scale oxides and, moreover, the correlation between the remarkably inhibiting effects of the nanometer-scale oxides on the thermal aging hardening of ODS steels and the formation of core-shell precipitates during the process of the long-term of thermal aging. Consequently, the important guidelines of alloy design and, moreover, the methodology for improving the over-all performance of Fe-Cr-Al ODS steels can be obtained to meet the service requirements of the cladding of ATF of light water reactors.