Atomistic Simulations of the Strengthening Effect of High-Density Bubble Formation in Helium-Irradiated Single Crystalline Copper

We conducted atomistic simulations to examine the strengthening effect of He bubbles with varying He atom concentrations in a single crystal copper matrix. Uniaxial tensile tests showed mechanical strengthening and enhanced ductility in copper with high-density He bubbles. The yield strength and failure strain increased up to a vacancy/He ratio of 1:3, but sharply decreased at a ratio of 1:4. High-density He bubbles formed 3D regions with distinct crystallographic orientations. Sessile dislocations formed at the boundaries of these regions for samples with vacancy/He ratios of 1:2 and 1:3, contributing to mechanical strengthening along with Cu/He interfacial energetics. Higher He concentrations also increased total dislocation density and reduced dislocation mobility, promoting homogeneous plastic deformation. During plastic flow, He bubbles underwent significant decrystallization, detwinning, and formation of Shockley partials, while copper exhibited typical dislocation-mediated plasticity. The growth rate of He bubbles significantly influenced plastic deformation and led to sample failure through bubble coalescence.