低活化马氏体钢中位错对氦辐照缺陷的影响

Effect of dislocation on helium irradiation defects in low-activation martensitic steel

低活化马氏体钢具有较好的抗辐照性能,然而对其抗辐照机理尚不清楚,特别是嬗变气体存在的情况下辐照缺陷行为非常复杂.本文通过对低活化马氏体钢预形变(10%和20%)后热处理(723 K,1 h)保留位错缺陷,随后对预留位错的样品进行室温氦辐照(50 keV,1×10^(17)He/cm^2),采用同步辐射掠入射X射线衍射、慢正电子多普勒展宽谱和热脱附谱研究了位错与氦辐照缺陷的相互作用及位错对氦原子迁移、热脱附行为的影响.结果表明,高密度位错阻碍了氦和氦空位复合体的扩散,进而减缓了辐照损伤的扩展,这种现象随着位错密度的增大更加明显.低活化马氏体钢在1179 K时发生体心立方结构→面心立方结构相转变,位错密度增加会导致由相转变引起的氦热脱附峰前移.未形变、10%形变、20%形变样品中氦的滞留量分别为10.3%,15.7%,17.9%,表明高密度位错更容易将氦保留到材料内部,反映了位错对氦的滞留起到促进作用.

Reduced-activation martensitic steel is a main candidate structural material for key components of advanced nuclear energy systems because of its good mechanical properties at room temperature,low neutron activation characteristics and satisfactory radiation resistance.In this work,we study the interaction between dislocations and helium-irradiation-induced defects in the steel and the effect of dislocations on the behavior of helium migration and desorption.The well-annealed samples are pre-deformed to 10%and 20%reductions in thickness by using cold rolling mill.After pre-deformation,samples are heat-treated to remove vacancy defects and retain dislocation defects.Then,the samples with reserved dislocations are irradiated with helium at room temperature(50 keV,1×10^(17)He/cm^(2)).After irradiation,the samples are characterized by synchrotron radiation grazing incident X-Ray diffraction,positron annihilation Doppler broadening spectroscopy,and thermal desorption spectroscopy.The results show that dislocations hinder the diffusion of helium and helium-vacancy complexes,and reduce the accumulation of radiation damage.Such an effect becomes more significant with the increase of dislocation density.The BCC→FCC phase transition of low activation martensitic steel occurs at 1179 K.The increase of dislocation density will lead to the forward shift of helium desorption peak induced by phase transition.The retention of helium in the undeformed sample,10%deformed sample and 20%deformed sample is 10.3%,15.7%and 17.9%,respectively,indicating that high density dislocations promote the retention of helium.