Ion-Beam Radiation-Induced Eshelby Transformations: The Mean and Variance in Hydrostatic and Shear Residual Stresses

TL;DR

This paper uses molecular dynamics simulations to develop a tensorial model of ion-beam radiation-induced residual stresses, revealing anisotropic effects and shear transformation strains that are crucial for nanoscale fabrication.

Contribution

It introduces a comprehensive tensorial framework to describe anisotropic residual stresses and shear strains caused by ion-beam irradiation, advancing beyond previous hydrostatic-only models.

Findings

Ion beam response is anisotropic and depends on beam direction.

Radiation induces shear transformation strains alongside hydrostatic expansion.

Defects cause residual shear stresses modeled as Eshelby inclusions.

Abstract

Ion beam plays a pivotal role in ion implantations and the fabrication of nanostructures. However, there lacks a quantitative model to describe the residual stresses associated with the ion-beam radiation. Radiation-induced residual stress/transformation strain have been mostly recognized in the hydrostatic sub strain space. Here, we use molecular dynamics (MD) simulations to show that the response of a material to irradiation is generally anisotropic that depends on the ion-beam direction, and should be described using tensorial quantities. We demonstrate that accelerator-based ion beam irradiation, combined with the intrinsic lattice anisotropy and externally induced anisotropy (such as anisotropic mechanical loadings), causes radiation-actuated shear transformation strains in addition to hydrostatic expansion. We map out these complex correlations for several materials. Radiation-induced defects are shown to be responsible for residual shear stresses in the manner of Eshelby inclusion transformation. We propose such tensorial response model should be considered for accurate nanoscale fabrication using ion-beam irradiation.