THE EFFECTS OF PRE-STRAIN ON TENSILE PROPERTIES OF NEUTRON IRRADIATION HIGH-PURITY ALUMINUM1)

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.