中文摘要：

为探明压水堆核电站一回路管道用钢在模拟工况环境下的热老化行为,以主管道用Z3CN20-09M奥氏体不锈钢为研究对象,对其在400℃、16.5 MPa含硼离子水蒸气中热老化不同时长后的显微组织、纳米压入硬度和冲击吸收功的变化规律进行了研究.利用扫描电子显微镜观察了热老化不同时长后的冲击断口形貌.试验结果表明：与原始态对比,经模拟工况热老化后Z3CN20-09M钢的铁素体相尺寸、分布和形态均无明显变化,而基体中位错密度随老化时长降低,老化过程中基体和位错线上有第二相的析出,且在老化3 000h时发生调幅分解,生成富Cr的α′相与富Fe的α相;铁素体相的纳米硬度随老化时间的增加由3.43GPa增加至6.08GPa,奥氏体相由3.02GPa增加至3.49GPa;冲击吸收功Akv随老化时间的延长由397.5J降低至214.0J.断裂形式由具有拉长韧窝特征的微孔聚集型韧性断裂,逐渐转变为具有解理台阶、鱼骨状花样和撕裂棱特征的准解理断裂.引起力学性能和断裂方式变化的主要原因是调幅分解生成的α′脆性相.

英文摘要：

In order to explore the thermal aging behavior of Z3CN20-09 Msteel used in nuclear power circuit pipeline in simulative running environment,in different thermal aging time in 400 ℃ and 16.5MPa water vapor,the metallographic structure and substructure of this steel were respectively observed,and the nano-indentation hardness and charpy impact energy were measured.It can be concluded：In the simulation working condition,with the increase of the thermal aging time,metallographic structure had little change,but substructure observation showed that the density of dislocation reduced,the second phase precipitated in matrix and dislocation line,spinodal decomposition happened in ferrite phase and generatedα′phase rich in Cr andαphase rich in Fe.With the increase of the thermal aging time,nanoindentation hardness of ferrite phase increased from 3.43 GPa to 6.08 GPa and austenite phase increased from 3.02 GPa to 3.49 GPa,while the charpy impact energy decreased from 397.5J to 214.0J.The form of the fracture transformed from ductile fracture to quasi-cleavage fracture and cleavage fracture.The main reason for the change of mechanical property and fracture form was the brittleα′phase generated in the spinodal decomposition.