Kinetics Governed by Elastic Bias in In-Situ Electron Irradiated Aluminium: A Coupled Experimental and Modeling Study

In this study, we investigate the direct in-situ formation of nanometer-scale radiation damage, including voids and loops, using a High-Resolution Transmission Electron Microscope (HRTEM). We observe a size-dependent effect on the shape of cavities induced by electron irradiation, with non-truncated and cross shapes appearing at sizes below 2 nm, while larger sizes exhibit truncated shapes, consistent with DFT based-equilibrium shapes. This effect is explained by our multi-scale modelling, considering the effects of finite size and network discretization on void shapes. The observed dispersion in cavity shape during their growth and shrinkage is primarily influenced by magic numbers, determined by geometry and network frustration. Additionally, not only the voids but also loops were followed in-situ. Loops grow until they eliminate at the surface, while voids go through periodic growth and shrinkage. We demonstrate that the evolution of both objects is linked and governed by elastic bias. The unexpected void shrinkage is attributed to the change of the main sink for the elimination of interstitials. Void growth occurs when the main sinks for interstitials are the strongly biased dislocation loops, generating a stronger vacancy flux towards voids. Conversely, cavity shrinkage occurs when the loops are absent, and the main sinks for interstitials are the foil surface, generating a stronger interstitials flux towards voids.<br/>We reproduce accurately this phenomenon through Object-Kinetic Monte Carlo (OKMC) modelling.