A mechanism of formation and properties of the void lattice in metals under irradiation

Abstract

We propose a new mechanism of interaction between voids, which is based on the elastically induced absorption of self-interstitial dislocation loops (SIA-loops) from the matrix. The main peculiarity of this dislocation interaction is its rigid relation to the crystal structure, namely, it arises only in the crystals, where SIA-loops can glide, and exists only between voids lying along the same loop-gliding directions. Void ordering is shown to originate from competition between the dislocation interaction and radiation-induced diffusion coarsening of voids, which leads to shrinkage of unfavourably positioned voids, if the void density exceeds the critical value. Voids in the superlattice thus formed have immediate neighbours along the loop-gliding directions, copying the host lattice due to the coincidence of the loop-gliding directions with close-packed directions of the matrix. The proposed model explains why the superlattice forms more readily in bcc than fee metals and gives analytical expressions for the void lattice parameter and stationary size, being in good agreement with experimental data over the whole temperature range of superlattice formation.