Mechanical behavior of long-term neutron-irradiated Al-Mg-Si alloy under compression

Abstract

The mechanical behavior of Al-Mg-Si alloy after long-term neutron irradiation (i.e. LT21 aluminum alloy served in the reactor for nearly 30 years) under compression loading with different temperature and strain rates is experimentally studied using material test system and split Hopkinson pressure bar. The effects of temperature and strain rate on its yield strength and flow stress are obtained. The results show that the material exhibits obvious temperature effect within a temperature rang from −40 ℃ to 300 ℃ and positive strain rate effect in a strain rate rang from 0.001 to 3 000 s−1, respectively. At a lower temperature range (from −80 to −40 ℃) and higher strain rates (from 3 000 to 5 000 s−1), the mechanical properties are insensitive to changes in temperature and strain rate. When the temperature reaches 300 ℃, the plastic deformation behavior of the material tends to ideal plastic flow. Based on the above experimental results, a modified Zerilli-Armstrong constitutive model considering irradiation damage is established by taking into account the effect of microscale irradiation defects on the mechanical properties of materials. The Zerilli-Armstrong model predictions are in good agreement with the experimental results. Furthermore, the yield strength of LT21 aluminum alloy with different fast neutron irradiation doses and the yield strength of another two samples obtained from different irradiated regions within the reactor at different strain rates and temperature are calculated by reference to the evolution of microscale irradiation defects of high purity aluminum. The above research shows that the Zerilli-Armstrong constitutive equation considering radiation damage established in this paper can not only establish the relationship between macroscale stress and strain, strain rate and temperature of the Al-Mg-Si alloy after long-term neutron irradiation, but also describe the dislocation motion and the mechanism of irradiation hardening. It can provide reference for the design, operation and safety evaluation of the corresponding structural elements in the nuclear reactor.