Dose and compositional dependence of irradiation-induced property change in FeCr

TL;DR

This study investigates how irradiation affects the mechanical and lattice properties of Fe and FeCr alloys across a wide dose range, revealing dose-dependent hardening and strain behaviors relevant for nuclear reactor materials.

Contribution

It provides experimental data on irradiation-induced property changes in FeCr alloys, including dose-dependent lattice strain and hardness, and compares results with theoretical models.

Findings

Irradiation hardening occurs even at very low doses.

Lattice strain peaks at 0.8 dpa and then decreases.

NRT efficiency for FeCr is 0.2, consistent with literature.

Abstract

Ferritic/martensitic steels will be used as structural components in next generation nuclear reactors. Their successful operation relies on an understanding of irradiation-induced defect behaviour in the material. In this study, Fe and FeCr alloys (3-12%Cr) were irradiated with 20 MeV Fe-ions at 313 K to doses ranging between 0.00008 dpa to 6.0 dpa. This dose range covers six orders of magnitude, spanning low, transition and high dose regimes. Lattice strain and hardness in the irradiated material were characterised with micro-beam Laue X-ray diffraction and nanoindentation, respectively. Irradiation hardening was observed even at very low doses (0.00008 dpa) and showed a monotonic increase with dose up to 6.0 dpa. Lattice strain measurements of samples at 0.0008 dpa allow the calculation of equivalent Frenkel pair densities and corrections to the Norgett-Robinson-Torrens (NRT) model for Fe and FeCr alloys at low dose. NRT efficiency for FeCr is 0.2, which agrees with literature values for high irradiation energy. Lattice strain increases up to 0.8 dpa and then decreases when the damage dose is further increased. The strains measured in this study are lower and peak at a larger dose than predicted by atomistic simulations. This difference can be explained by taking temperature and impurities into account.