Self-ion irradiation effects on nanoindentation-induced plasticity of crystalline iron: A joint experimental and computational study

TL;DR

This study combines experiments and multi-scale simulations to explore how ion irradiation affects the nanoindentation plasticity of crystalline iron, revealing dislocation mechanisms and increased hardness due to irradiation.

Contribution

It provides new insights into the atomic-scale dislocation processes and mechanical response of irradiated iron through integrated experimental and computational approaches.

Findings

Irradiation causes a sudden displacement burst during nanoindentation.

Dislocation nucleation and mobilization are key to increased hardness.

Simulations qualitatively agree with experimental GNDs density images.

Abstract

In this paper, experimental work is supported by multi-scale numerical modeling to investigate nanomechanical response of pristine and ion irradiated with Fe2+ ions with energy 5 MeV high purity iron specimens by nanoindentation and Electron Backscatter Diffraction. The appearance of a sudden displacement burst that is observed during the loading process in the load-displacement curves is connected with increased shear stress in a small subsurface volume due to dislocation slip activation and mobilization of pre-existing dislocations by irradiation. The molecular dynamics (MD) and 3D-discrete dislocation dynamics (3D-DDD) simulations are applied to model geometrically necessary dislocations (GNDs) nucleation mechanisms at early stages of nanoindentation test; providing an insight to the mechanical response of the material and its plastic instability and are in a qualitative agreement with GNDs density mapping images. Finally, we noted that dislocations and defects nucleated are responsible the material hardness increase, as observed in recorded load-displacement curves and pop-ins analysis.