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中文核心期刊

预应变对中子辐照高纯铝拉伸性能的影响

THE EFFECTS OF PRE-STRAIN ON TENSILE PROPERTIES OF NEUTRON IRRADIATION HIGH-PURITY ALUMINUM

  • 摘要: 金属材料的中子辐照硬化和脆化一直都是核能安全领域十分关注的重要问题之一. 为了进一步认识预应变对中子辐照金属材料塑性形变和最终断裂特性的影响规律, 及其微观机理, 本文研究了10%拉伸预应变高纯铝的拉伸应力-应变曲线、失稳应力和失稳应变等随辐照剂量的变化规律. 结果表明, 辐照剂量越高, 预应变高纯铝内部孔洞的尺寸和数密度越高, 导致屈服强度和极限拉伸强度越高, 均匀延伸率和失稳应变越小, 表现出典型的辐照硬化和脆化效应, 但失稳应力与辐照剂量几乎无关. 相同辐照剂量条件下, 预应变引入的高密度位错能够显著降低辐照孔洞的尺寸和数密度, 加之辐照退火效应的综合影响, 导致预应变能够降低高纯铝屈服强度的增长率和失稳应变的下降率, 从而表现出一定的抑制辐照硬化和脆化的能力, 预应变还能够提高高纯铝的失稳应力, 但整体而言预应变并不能提高高纯铝的延性. 最后, 基于J-C本构模型的中子辐照退火态金属材料的脆化模型能够直接应用于预应变金属材料, 且模型预测结果与实验结果吻合较好.

     

    Abstract: Neutron irradiation hardening and embrittlement of metallic materials is very important in the field of nuclear energy and safety. In order to further understand the effects of pre-strain on the plastic deformation and fracture characteristics of neutron irradiated metals and its microscopic mechanism, the tensile stress-strain, plastic instability stress and plastic instability strain of tensile pre-strain high-purity aluminum with different doses were studied in this paper. The results showed that a higher dose results in a higher density and size of voids, a higher yield strength and ultimate tensile stress, a smaller elongation ratio and plastic instability strain, which showed a typical radiation hardening and embrittlement effects, but the plastic instability stress was almost independent of dose. Under the same dose, the high density of dislocation inducing by pre-strain could significantly reduce the size and density of voids, coupling the irradiation annealing effect, that resulted in the pre-strain could reduce the growth rate of yield strength and the falling rate of plastic instability strain, which means the pre-strain could inhibit irradiation hardening and irradiation embrittlement of neutron irradiated high-purity aluminum to a certain degree, but the pre-strain could not improve ductility of high-purity aluminum. Finally, the neutron irradiation embrittlement model for annealed metals basing on Johnson-Cook constitutive model could be directly applied to pre-strain metal materials, and the predicted results of present model agreed well with the experimental data. This means the neutron irradiation embrittlement model for metals basing on Johnson-Cook constitutive model can predict the whole true stress-strain curve, and the fracture true strain of the irradiated annealed and pre-strain metal materials by using the true stress-strain of unirradiated annealed metal and the yield strength of metals with different doses and pre-strain only. That is very important in the field of estimating and predicting safety of nuclear reactor.

     

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