核反应堆压力容器模拟钢中富Cu纳米团簇析出早期阶段的研究

采用调质处理后热时效模拟方法,用原子探针层析成像技术研究了核反应堆压力容器模拟钢中富铜纳米团簇的析出过程.模拟钢经880℃加热水淬,660℃高温回火调质处理,并经400℃时效处理1000 h后基体中析出了富铜纳米团簇.使用MSEM(maximum separation envelope method)方法重点研究了富铜纳米团簇在析出早期阶段成分变化规律.结果表明,富铜纳米团簇容易在镍含量较高的位置形核,并随着富铜纳米团簇中铜原子聚集程度的增加,纳米团簇中心处铜含量逐渐增加,镍含量逐渐减少;在纳米团簇与α--Fe基体界面处,镍和锰含量逐渐增加,形成了富镍和富锰包裹富铜纳米团簇的结构.结合实验结果讨论了压力容器钢中合金元素镍及杂质元素磷会增加中子辐照脆化敏感性的原因.

Study on the early-stage of copper-rich nano-clusters precipitation in model nuclear reactor pressure vessel steel

Early-stage formation of Cu-rich nano-clusters in thermal aging nuclear reactor model pressure vessel steel quenched and tempered was investigated by atom probe tomography (APT). After the initial heat treatment at 880 ℃ for 0.5 h and water quenching, the materials were tempered for 10 h at 660 ℃ and air cooled. Cu-rich nano-clusters were observed in the samples aged at 400 ℃ for 1 000 h. The change in composition of the steel in the early-stage of precipitation of Cu-rich nano-clusters was studied by the maximum separation envelope method (MSEM). Cu nanoclusters are observed to form from high nickel regions. The Cu concentration increases and the Ni concentration decreases at the central cores with increasing Cu atoms congregation. Ni and Mn atoms aggregation on the exterior side of the cluster/matrix interface is also evident. Based on experimental results, the reason that Ni and P can increase the sensitivity to neutron irradiation embrittlement of the nuclear reactor pressure vessel steel is discussed.