Mechanisms of helium nanobubble growth and defect interactions in irradiated copper: A molecular dynamics study

Abstract

It is well-established that mechanical behavior of the materials is significantly affected under irradiation. This is often due to the growth of nanobubbles that changes the microstructure of the irradiated materials. In this work, growth of helium nanobubbles with different sizes and helium to vacancy (He/V) ratios in copper is investigated using molecular dynamics (MD) simulations. Our simulations reveal that the nanobubble growth is accommodated by nucleation of various types of defects such as: stacking fault octahedron (SFO), dislocation network, punched-out dislocation loop, stacking fault tetrahedron (SFT) etc. around the nanobubbles. We also unveil the mechanisms of formation as well as punching-out of the dislocation loops, and further show that such defects are activated beyond a threshold of bubble size and He/V ratio. In final, we propose an equation of state (EOS) for predicting the pressure of the nanobubbles inside copper from the input bubble size, He/V ratio, and temperature.