Change of the Mechanical Properties by Annealing in Internally-Oxidized and Neutron-Irradiated V-2 wt%Zr Alloy

Abstract

An internally oxidized V-2 wt%Zr alloy, together with an un-oxidized alloy of the same composition and pure vanadium, irradiated to 7×10²⁰ neutrons/cm² (E_n>1 MeV) at about 513 K and then annealed for 3.6×10³ s (1 h) at various temperatures up to 973 K, was tensile-tested at room temperature. The tensile properties were considered, referring to the change of electrical resistivity in cumulative isochronal annealing of the irradiated alloys. Electron micrographs of the internally oxidized alloy, irradiated to 1.2×10²¹ neutrons/cm² at about 673 K and subsequently annealed, were also referred. The results obtained are as follows:
(1) The strength versus annealing temperature curve for the internally oxidized alloy showed two peaks, the larger one at 573 K and the smaller one at 723 K, which were thought to result from an interaction between radiation-induced defects and interstitial impurities, especially oxygen dissolved in the alloy by the internal oxidation process. The un-oxidized alloy did not show any hardening peaks on the curve, because of the scavenging effect of zirconium as reported for titanium in the previous work.
(2) Correspondingly, a large decrease of electrical resistivity, measured at 77 K, was observed in the internally oxidized alloy annealed at about 510 K, while a decrease in electrical resistivity was observed at about 740 K in the un-oxidized alloy. Part of the latter decrease might be attributed to the internal oxidation of zirconium in the alloy during annealing.
(3) Electron microscope observation revealed that many dislocations, tangling around dispersed particles, and defect clusters were produced by the irradiation in the internally oxidized alloy.