Investigation of Irradiation Hardening and Embrittlement of Zr-2.5%Nb Alloy with High-Energy (e,γ)-Beams

Abstract

The paper researches into the effect of the initial structural condition of Zr-2.5%Nb alloy, which is widely used in reactor engineering to manufacture reactor core components (mainly as a structural material for RBMK and CANDU pressure tubes), and of irradiation conditions (temperature, applied stress) on irradiation hardening and embrittlement. The reactor damage of Zr-2.5%Nb alloy was modeled with a method of high-energy 225 MeV (e,γ)-beam irradiation, which allows samples to be irradiated under strictly controlled stress conditions. The research has been carried out on Zr-2.5%Nb alloy exposed to four types of thermo-mechanical treatment. It has been found that the alloy is susceptible to intensive irradiation embrittlement irrespective of its initial condition, and the intensity of Zr-2.5%Nb irradiation hardening greatly depends on pre-treatment. In contrast to other conditions, Zr-2.5%Nb alloy is virtually not susceptible to irradiation hardening after high-speed high-frequency (SHF) heating, quenching, and subsequent annealing in the high-temperature range of the α-region, during which the double-phase α+βNb state with high dispersion of βNb (∼1023 m−3) precipitates develops. The obtained results are in good agreement with the post-reactor irradiation tensile test results. The study demonstrates the efficiency of high-energy (e,γ)-beam irradiation for investigating the irradiation hardening and embrittlement of zirconium alloys.