Ni对RPV模拟钢中富Cu原子团簇析出的影响

Effect of Nickel Alloying Element on the Precipitation of Cu-Rich Clusters in RPV Model Steel

用原子探针层析技术和时效模拟方法,研究了不同N i含量并且提高了Cu含量的反应堆压力容器(RPV)用模拟钢中富Cu、富N i和富Mn原子团簇的形成。结果表明,提高钢中的N i含量会促使富Cu原子团簇的析出,富Cu原子团簇中含有N i和Mn。实验检测到富N i的原子团簇,团簇中含有Cu和Mn,富N i原子团簇可以作为富Cu原子团簇析出时的形核区。实验还检测到富Mn原子团簇,当Mn原子团簇中含有较高的N i时,它也可以成为富Cu原子团簇析出时成核的地方。由于钢中的合金元素N i在形成富N i原子团簇后会成为富Cu原子团簇析出时成核区,因而提高N i的含量将促进富Cu原子团簇的析出,这是合金元素N i会增加压力容器钢中子辐照脆化敏感性的本质原因。

The effect of nickel alloying element on the precipitation of Cu-rich clusters in RPV model steel has been in- vestigated by means of atom probe tomography. 40 kg ingots of RPV model steel were prepared by vacuum induction furnace melting with two different Ni contents （0. 79 wt. % and 1.52 wt. % ） and with higher Cu content （0. 5 wt. % ）. The specimens of 50 × 40 mm^2 , 4 mm in thickness, were heat-treated by 880 -20 min water quenching, 660℃ - 10 h tempering, and 400 ℃ aging, different from 100 h to 2 000 h. The results show that the increase of nickel content in RPV model steels will promote the precipitation of Cu-rich clusters. The contents of Ni and Mn were detected in the Cu-rich clusters at the early stage of the precipitation. Ni-rich clusters containing Cu and Mn were detected, and they could act as the nucleation sites for the precipitation of Cu-rich clusters. Mn-rich clusters could also be detected. Mn-rich clusters were not the nucleation sites for the precipitation of Cu-rich clusters, but the segregation of Cu atoms in those Mn-rich clusters containing much higher Ni could be found. Ni-rich clusters would act as the nucleation sites during the precipitation of Cu- rich clusters; therefore the increase of nickel content in RPV steels could promote the precipitation of Cu-rich clusters. This is the essential reason that the presence of nickel in PRV steel could increase its sensitivity to neutron irradiation embrittlement.