核能作为目前全球最安全环保经济的能源之一，其发展和使用受到了全球范围内的广泛关注，而严重制约核电及核能发展的首要问题是材料。在核电站系统中，阀门阀杆作为控制堆内的运动部件，其性能的优越直接影响到反应堆的安全经济运行，国外已发现多起由于热老化脆化导致的阀杆断裂现象。本项目基于核电站内服役后的阀杆材料17-4PH马氏体不锈钢的性能数据和微观结构信息等先期研究结果，旨在深入探究富铜析出物的形成演化，以及与富铬α’相的协同作用对材料脆化行为的影响机制。通过设计层状合金及界面，利用三维原子探针技术、小角中子散射原位拉伸等先进表征手段，获取材料在热时效后或断裂变形过程中，富铜析出物在富铬α’相界面处的分布、结构演化等信息，阐明富铜析出物与富铬α’相界面的协同作用机理。该科学问题的解决将有助于更深层次的理解核电站内长时间服役后17-4PH马氏体不锈钢的热老化脆化机理，为此类材料的发展提供理论指导。

Nuclear energy is one of the safest and green energy in the world, which has attracted worldwide attention for its development and use. Material is the primary problem that seriously restricts the development of nuclear power and nuclear energy. In the nuclear power plant, the valve stem is used as a moving part for controlling in reactor. Its superiority on performance directly affects the safe operation of the reactor. Much fracture of valve stem caused by thermal aging embrittlement has been found in foreign nuclear power plants. In this work, the formation and evolution of copper-rich precipitate, and the synergistic effect of copper-rich precipitate and chromium-rich α' phase interface on embrittlement behavior have been studied, which is based on the performance data and microstructural information of 17-4PH martensitic stainless steel obtained from valve stem in service in nuclear power plants before. For designed lamellar alloy and interface, three-dimensional atomic probe technology and small angle neutron scattering in-situ observation are used for obtaining the distribution and microstructure evolution of copper-rich precipitate at the interface of chromium-rich α' phase after thermal aging or during deformation process. The aim is to clarify the synergistic effect of copper-rich precipitate and chromium-rich α' phase interface. Solving the scientific problem will contribute to a deeper understanding on thermal aging embrittlement mechanism of 17-4PH martensitic stainless steel serviced in nuclear power plant. It can provide important theoretical guidance for the material improvement.