Dislocation-accelerated void formation under irradiation in zirconium

Molecular dynamics simulations have been performed to model defect creation in alpha zirconium with tensile strains comparable to the elastic strains near the interfaces between zirconium and hydrides. Irradiation-induced vacancy clusters under the strain field could be initiation sites for dislocation nucleation, and the gliding of these dislocations provides channels for transporting atoms from the cascade core, significantly accelerating the growth of vacancy clusters to form a void. The critical number of vacancies in a cluster that is enhanced to grow by the external stress is estimated. The present results provide an atomic-level mechanism to explain the stress-enhanced void growth under irradiation in zirconium, as observed in experiments. The acceleration of delayed hydride cracking under irradiation might be partially attributed to the formation of these voids.