中子辐照和冷轧(预应变)对高纯铝压缩特性的影响

THE EFFECTS OF NEUTRON IRRADIATION AND PRE-STRAIN ON COMPRESIVE CHARACTERISTIC OF HIGH-PURITY ALUMINUM

金属材料的中子辐照脆化一直都是核能安全领域十分关注的问题,辐照硬化效应往往能够定性表征材料的辐照脆化性能.大量冷轧金属被应用于反应堆结构材料,为进一步认识冷轧(预应变)对中子辐照金属材料硬化特性的影响规律及其微观机理,文章研究了退火态和预压缩10%应变高纯铝的准静态压缩性能,以及位错密度,辐照孔洞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,高纯铝内部孔洞的尺寸和数密度越高,辐照缺陷引起的强化效果越强;预应变引入的高密度位错会抑制辐照孔洞的形核和长大,最终降低孔洞的尺寸和数密度;预应变高纯铝表现出显著的辐照退火效应,随着辐照剂量的增加,辐照退火引起的软化效应明显强于辐照缺陷引起的硬化效应,导致预应变高纯铝的屈服强度随辐照剂量先增加后降低;这一结果暗示退火效应很可能导致辐照冷轧材料的屈服强度低于其未辐照时的初始屈服强度,从而降低反应堆内冷轧态金属结构的安全可靠性.最后,基于Johnson-Cook本构关系的B-Y(Byun-Ye)辐照脆化模型能够适用于辐照金属材料的压缩本构关系预测,且模型预测结果与实验结果吻合较好.

Neutron irradiation embrittlement of metal materials is very important in the field of nuclear energy safety,and irradiation hardening could often be used to qualitatively express irradiation embrittlement.Due to a large number of cold-rolled metals have been used in nuclear reactor,and in order to further understand the effects of cold rolling(prestrain)on the hardening characteristics of neutron irradiation metal materials and its microscopic mechanism,the quasistatic compressive stress-strain relationships of annealed and pre-compressed 10%strain high purity aluminum with different doses were tested,as well as the variation of dislocation density,irradiation void size and number density were also studied in this paper.The results showed that a higher dose induced a bigger size and higher number density of voids,which resulting a stronger hardening effect.The high density dislocations introduced by pre-strain inhibited the nucleation and growth of irradiation voids,and finally reduced the size and number density.With the increase of dose,the softening effect caused by irradiation annealing was stronger than the hardening effect caused by voids,which led to the yield strength of pre-strained high purity aluminum first increasing and then decreasing with dose.Those implies that annealing effect may cause the yield strength of irradiated cold-rolled materials to be lower than that of non-irradiated materials,thus reduce the safety and reliability of cold-rolled metal structures in nuclear reactors.Finally,the B-Y(Byun-Ye)irradiation embrittlement model basing on Johnson-Cook constitutive can be used to predict the compressive constitutive relation of irradiated metal materials,and the prediction effect are in good agreement with the experimental results.