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对核电站压水堆一回路用Z3CN20-09M铸造双相不锈钢进行400℃恒温加速热老化试验,持续加热时间分别为1000h和3000h,利用透射电镜(TEM)分析其在不同热老化时间下亚结构的变化,以及热老化过程对亚结构的影响。结果显示,热老化过程中显微组织形态无明显变化,为奥氏体基体上分布着不连续的岛状铁素体,但亚结构发生了明显改变。奥氏体基体在热老化初期有大量位错缠结及高密度的层错,随热老化时间的延长,基体中的位错缠结程度明显减轻,层错数量大大减少,在位错、相界及晶界上有析出物出现,铁素体相内出现调幅分解。
A series of Z3CN20-09M cast duplex stainless steel was used to carry out thermal aging accelerated test at 400 ℃ for 1000h and 3000h, respectively. The thermal aging of sub-structures at different thermal aging time was analyzed by transmission electron microscope (TEM) Changes, and the impact of the thermal aging process on the substructure. The results show that there is no obvious change of the microstructure during heat aging, and the discontinuous island-like ferrite is distributed on the austenite matrix, but the sub-structure obviously changes. In the early stage of thermal aging, the austenite matrix has a large number of dislocation entanglements and high-density layer faults. As the thermal aging time prolongs, the degree of dislocation entanglement in the matrix is significantly reduced, and the number of layer faults is greatly reduced. Boundaries and grain boundary precipitates appear, the ferrite phase amplitude modulation decomposition.