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

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.