Characterisation of Irradiation Damage in Fe3Cr and Fe5Cr: A Study on the Effects of Chromium Content and Temperature

TL;DR

This study investigates how chromium content and temperature influence irradiation damage in Fe-Cr alloys, revealing non-monotonic strain and hardness changes and highlighting the complex defect evolution mechanisms relevant to fusion materials.

Contribution

It provides a direct comparison of Fe-3%Cr and Fe-5%Cr alloys under irradiation across a temperature gradient, elucidating the combined effects of Cr content and temperature on damage evolution.

Findings

Strain and hardness decrease up to ~300C, then increase beyond.

Fe-3%Cr exhibits higher strain and hardening than Fe-5%Cr.

Damage stabilization occurs through solute-defect clustering and cavity formation.

Abstract

Fe-Cr binary alloys serve as simplified model systems to study irradiation damage relevant to fusion structural materials. Here, Fe-3%Cr and Fe-5%Cr samples were irradiated with 4 MeV Fe ions under a dose rate of 4x10^5 dpa/s across a linear thermal gradient (120C to 480C) in a single experiment, enabling direct comparison of temperature and Cr content effects under identical conditions. Depth-resolved Laue micro-diffraction (~10^4 strain sensitivity), nanoindentation, and AFM reveal non-monotonic evolution of lattice strain and hardness: both decrease with temperature up to ~300C, then increase beyond. This turning point reflects a shift from enhanced defect mobility and partial recovery to solute-defect clustering and cavity formation, which stabilize damage. Fe-3%Cr shows consistently higher strain and hardening than Fe-5%Cr, especially at lower temperatures. Minimal change in post-indentation pile-up indicates limited softening or localization. These results highlight how Cr content and temperature jointly affect irradiation response, offering new insights into defect evolution in fusion-relevant alloys.