Correlation of microstructural and mechanical properties of neutron irradiated EUROFER97 steel

Abstract

The reduced activation ferritic-martensitic (RAFM) steel EUROFER97 was neutron irradiated to an average dose of 16.3 dpa at temperatures from 250 °C to 415 °C. Radiation-induced defects such as dislocation loops and voids were characterized by transmission electron microscopy (TEM). The quantitative analysis of the microstructural results includes the determination of the Burgers vector, the size, number density of defects and the calculation of the relaxation volume of the loops or void swelling. The dislocation loops with b½⟨111⟩ Burgers vector were found in the material irradiated at 250 °C and 300 °C, while at higher temperatures a preferential formation of b<100> loops was observed. The voids were found only in material irradiated at 350 °C and 400 °C. The maximum relaxation volume of the loops and void swelling was measured for 350 °C. The dispersed barrier hardening (DBH) model was found to accurately predict the yield strength in the material irradiated at the temperatures ≥350 °C. The difference between experiment and DBH model at lower temperatures is due to the formation of nano-voids or interstitial loops with a size of <2 nm that are not recognizable in the TEM.