Evolution of stacking fault tetrahedra in irradiated nanoporous Au pillars under compression - A molecular dynamics study

This work explores the role of stacking fault tetrahedra (SFTs) on the deformation characteristics of irradiated nanoporous gold (NPG) structures using molecular dynamics (MD) simulations. Atomistic irradiated NPG structures were generated by incorporating a predefined number of SFTs based on the experimentally relevant SFT defect density adopted from literature. The stress-strain output from simulations demonstrates an initial elastic regime followed by a plateau region. However, it is observed that despite the presence of high density of SFTs, the overall mechanical properties of irradiated NPG structures remain close to pristine ones. In-depth dislocation analysis shows that the Shockley partial dislocations nucleate from the free surfaces as well as from the SFTs. Also, numerous SFT-dislocation interaction events are observed and thereby resulting in removal as well as reduction in the size of the SFTs. In a novel approach, the number of SFTs removed during the compression process is quantified. At a true compressive strain of 60%, nearly 40% of the SFTs are removed. On the other hand, not all the SFTs interact with the dislocations, instead they tend to undergo affine deformation along with the ligament or nodes. These observations are used to address the discrepancies between the existing experimental hardening behavior of irradiated NPGs and the unaltered mechanical behavior from the current MD study.