Atomistic investigation of the annihilation of non-screw dislocation dipoles in Al, Cu, Ni and γ-TiAl

Abstract

Annihilation of vacancy-type non-screw dipolar dislocations is studied with molecular dynamics in fcc metals Al, Cu and Ni, and intermetallic γ-TiAl. Contrary to common belief, dipoles do not simply disappear. Instead, they transform into a series of defects depending on their height, orientation and temperature. At low temperatures, hollow structures, reconstructed configurations and faulted dipoles are formed. At high temperatures, with the help of short-range diffusion, isolated or interconnected vacancy clusters and stacking-fault tetrahedra are formed within a simulation time of 1 ns. Employing saddle-point-search methods, the formation of the above by-products is explained by accelerated diffusion paths along the dipole cores.