Molecular Dynamics Study of Defect Evolution in Inconel 617 Alloy Under Successive Cascade Irradiation

TL;DR

This study uses simulations to explore how radiation damage accumulates in Inconel 617 alloy at the atomic level, revealing how defects evolve and affect material properties.

Contribution

The study reveals the asymmetric behavior of interstitial and vacancy defects under irradiation, and how interstitial clustering drives dislocation loop formation in Inconel 617.

Findings

Frenkel pair accumulation increases linearly with irradiation dose.

Interstitials form large clusters while vacancies remain isolated.

Dislocation density rises linearly and reaches a saturation point.

Abstract

Inconel 617 (IN617) is a promising structural material for advanced nuclear systems such as heat pipe-cooled reactors, but its fundamental defect evolution under neutron irradiation remains poorly understood. This study employs classical molecular dynamics simulations to investigate the atomic-scale irradiation damage mechanisms in a representative Ni–Cr–Co ternary model of IN617 under successive displacement cascades. The results reveal a near-linear accumulation of Frenkel pairs with dose, with the count increasing by a factor of approximately 24 from the first to the 75th cascade. A critical finding is the stark asymmetry in defect kinetics: interstitials rapidly coalesce into large clusters (with 88.4% of interstitials found in clusters of ≥ 2 atoms after 75 cascades), while vacancies remain predominantly isolated (constituting 68.8% of all vacancy defects). This disparity directly governs microstructural evolution, as interstitial cluster growth drives dislocation loop nucleation, leading to a linear rise in dislocation density to a saturated value of approximately 4.5 × 10−4 Å−2. The saturated dislocation structure subsequently undergoes continuous reorganization through reactions between partial dislocations. These insights demonstrate that irradiation hardening in IN617 under simulated conditions is governed primarily by interstitial-type defect clustering, providing a crucial mechanistic basis for assessing its performance in radiation environments.

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