中子辐照金属材料的脆化模型研究

金属材料的辐照脆化问题一直以来都是核能安全领域亟待解决的关键问题之一.为了更准确地预测金属材料的辐照脆化行为,基于Johnson-Cook本构模型,将未辐照金属材料的断裂真应力取作辐照材料的断裂真应力,建立了通过辐照退火态金属材料屈服强度就能够预测其整个真应力$\!$-$\!$-$\!$应变曲线,以及断裂真应变的辐照脆化模型.实验研究了不同中子剂量辐照退火态高纯铝的准静态拉伸真应力$\!$-$\!$-$\!$应变曲线、断裂真应力和断裂真应变随辐照剂量的变化规律.结果表明,辐照剂量越高,高纯铝的屈服强度越高,断裂真应变越低,但断裂真应力几乎不变.通过TEM显微分析获得了高纯铝内部辐照缺陷的尺寸和数密度随辐照剂量的变化规律,结果表明,辐照剂量越高,孔洞的尺寸和数密度越高,但位错环尺寸和数密度始终很小,难以准确统计.由辐照高纯铝实验数据拟合得到了辐照脆化模型所需参数,并检验了该模型的预测效果.结果表明,无论是通过实验还是显微分析得到辐照高纯铝的屈服强度,模型的预测结果均能够与实验结果较好地吻合,且模型对退火态高纯铝临界中子剂量的预测值也与文献结果一致. 

A MODEL OF NEUTRON IRRADIATION EMBRITTLEMENT FOR METALS1)

Irradiation embrittlement of metals is very important in the field of nuclear energy safety. In order to describe the irradiation embrittlement behavior of metals, a neutron irradiation embrittlement model for annealed metals was proposed based on Johnson-Cook constitutive model. The fracture true stress of the irradiated samples was taken as the same as the unirradiated sample. This model can predict the whole true stress-strain curve, and the fracture true strain of the irradiated annealed materials by using the yield strength only. The tensile true stress-strain curves, the fracture true stress, and the fracture true strain of high-purity aluminum with different doses were measured by quasi-static tensile tests. The results showed that a higher dose results in a higher yield strength and a lower fracture true strain. However, the fracture true stress is almost unchangeable. The size and number density of irradiation-induced defects for high-purity aluminum with different doses were mearsured by TEM microscope. The results showed that a higher dose results in a higher size and a higher number density of voids, but the size and the number density of dislocation loops were difficult to measure accurately due to their size and number density are too small. The parameters of this model were fitted by experimental data of high-purity aluminum, and the application effect of this model was checked. The predicted results of this model agree well with the experimental data, regardless wtether the yield was obtained by quasi-static tensile tests or by the size and number density of irradiation-induced defects. The critical irradiation dose of annealed high-purity aluminum predicted by this model also agrees well with literature.