高Cr铁素体钢是先进核电机组的首选结构材料之一。瞬时液相（TLP）扩散连接接头的组织与性能与母材接近，并可避免传统熔化焊由于高温热循环导致的接头性能劣化。TLP中间层中含有大量降熔元素，对接头蠕变过程中的组织演变及性能退化具有重要影响。据此，本项目拟对高Cr铁素体钢TLP接头组织的形成、演化，及其对接头蠕变断裂机制的影响开展研究：探究连接过程中降熔元素动态扩散、非平衡偏聚及过饱和析出的动力学行为，综合考虑降熔元素富集对界面移动的溶质拖曳及沉淀钉扎效应，澄清接头组织形成机制；阐明高温蠕变条件下的接头组织演变规律，澄清降熔元素的浓度场分布对组织演化行为的影响，揭示TLP接头性能退化的微观机制，并从显微组织退化的角度澄清TLP接头蠕变断裂机制。本项目的顺利实施将有助于加深高Cr铁素体钢TLP接头组织演变机制的理论认知，为高Cr铁素体钢TLP接头蠕变断裂机制及服役可靠性研究提供理论及试验支撑。

High Cr ferritic steel is one of the preferred structural materials for advanced nuclear power plants. The microstructures and mechanical properties of the transient liquid phase (TLP) diffusion bonding joint is close to that of base metal. Furthermore, TLP bonding would avoid the deterioration of joints caused by the high temperature thermal cycle during the traditional fusion welding. However, high contents of the melting point depressant elements in the interlayer for TLP bonding affect the microstructural evolution and performance degradation in the process of creep at high temperature. Hence, the present project will study on formation and evolution of microstructure in the TLP bonding joint of the high Cr ferritic steel, and the effects of which on creep fracture mechanism. The kinetics and behaviors of the dynamic diffusion, non-equilibrium segregation and supersaturated precipitation of the melting point depressant elements during TLP bonding will be researched. On consideration of the effect of solute drag and precipitates pinning, caused by enrichment of the melting point depressant elements, on boundaries moving, the formation mechanism of joint microstructure will be clarified. The microstructure evolution of TLP joints under the condition of high temperature creep will demonstrated, and the influence of the concentration distribution of the melting point depressant elements on microstructural evolution will be clarified. The micro-mechanism for the mechanical properties’ degradation of TLP bonding joints will be revealed, and the creep fracture mechanism of TLP joints will be clarified from the perspective of microstructure degradation. The successful implementation of this project will help to improve the theory for the microstructural evolution mechanism in the TLP bonding joint of the high Cr ferritic steel, and provide theoretical and experimental support for creep fracture mechanism and service reliability of TLP bonding joints in the high Cr ferritic steel.