Radiation-induced defect evolution in metallic alloys is often interpreted in terms of thermally activated defect diffusion, cascade quenching, and defect recombination. However, athermal structural relaxation can also influence defect evolution, particularly in chemically complex alloys. In this work, we investigate defect evolution in face-centered cubic (fcc) Ni, Ni–Cr, and Ni–Fe alloys using atomistic simulations based on the creation-relaxation algorithm (CRA), in which Frenkel pairs are iteratively introduced into an initially pristine lattice followed by structural relaxation. This approach isolates a nondiffusive, athermal limit by suppressing long-range thermal migration and explicit displacement-cascade effects. By analyzing point defects, defect clusters, athermal recombination probabilities, elastic properties, and dislocation structures, we show that alloying produces modest changes in the total residual defect inventory, despite pronounced differences in bulk elastic properties. Instead, the stronger alloying effects appear in defect morphology, interstitial-cluster statistics, local recombination behavior, and Burgers-vector-resolved dislocation character. Higher Fe concentrations promote fewer but larger interstitial clusters and enhance local athermal recombination with interstitial clusters, whereas pure Ni and Ni–Cr show a higher frequency of smaller clusters. These results indicate that, within the athermal CRA framework, local chemical and elastic environments influence the pathways of defect relaxation and clustering, while their effect on the total surviving defect population remains modest compared with that observed under irradiation conditions where thermally activated processes are active.

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• Disclinations & dislocations
• Interstitials
• Microstructure
• Point defects
• Radiation damage