Atomistic Study of Radiation-Induced Ductile-to-Brittle Transition in Austenitic Steel

TL;DR

This paper uses molecular dynamics simulations to explore how neutron irradiation-induced defects in austenitic steel influence fracture mechanisms, shedding light on the ductile-to-brittle transition critical for nuclear material safety.

Contribution

It introduces a novel framework for quantifying fracture energy contributions in irradiated materials, linking defect types to changes in fracture behavior.

Findings

Voids promote crack growth by lowering cohesive energy.

Dislocation loops hinder crack propagation and alter crack paths.

The adapted fracture energy decomposition quantifies damage effects.

Abstract

Neutron irradiation in structural alloys promotes defect clustering, which suppresses plasticity and triggers a ductile-to-brittle transition (DBT), a key degradation mechanism limiting fracture resistance in nuclear materials. This study investigates the fracture mechanisms underlying this transition in irradiated Fe-Ni-Cr alloys. Using Molecular Dynamics simulations, we examine how different defect types influence crack propagation and energy dissipation mechanisms. The results reveal distinct roles of these defects: voids facilitate crack growth by reducing local cohesive energy, while dislocation loops act as barriers that impede crack advancement and redirect crack paths, significantly altering crack morphology. Building on the classical approach of separating fracture energy into brittle cleavage and plastic components, this study adapts the decomposition to irradiated materials. This framework quantifies the evolving contributions of surface energy and plastic work across increasing radiation damage levels, providing critical insight into how irradiation-induced defects govern fracture dynamics