Observation of transient and asymptotic driven structural states of tungsten exposed to irradiation

TL;DR

This study combines experimental and simulation methods to reveal how tungsten's structure evolves under irradiation, showing initial defect accumulation, fluctuating strains, and a stable driven state with specific defect configurations and volumetric changes.

Contribution

It provides new insights into the non-linear structural transformations and defect dynamics of tungsten under irradiation using combined experimental and atomic-scale simulation approaches.

Findings

Defect-induced deformations start above 0.02 dpa

Fluctuating strains occur around 0.1 dpa

A driven quasi-steady state forms above 1 dpa with specific defect structures

Abstract

Combining spatially resolved X-ray Laue diffraction with atomic-scale simulations, we observe how ion-irradiated tungsten undergoes a series of non-linear structural transformations with increasing irradiation exposure. Nanoscale defect-induced deformations accumulating above 0.02 displacements per atom (dpa) lead to highly fluctuating strains at ~0.1 dpa, collapsing into a driven quasi-steady structural state above ~1 dpa. The driven asymptotic state is characterized by finely dispersed vacancy defects coexisting with an extended dislocation network, and exhibits positive volumetric swelling due to the creation of new crystallographic planes through self-interstitial coalescence, but negative lattice strain.