Molecular dynamics simulation of a nonequilibrium grain boundary in titanium under the ultrasonic action

Abstract

Abstract Effect of oscillating tension-compression stresses on a nonequilibrium grain boundary containing a disclination dipole in titanium is studied by means of molecular dynamics simulations. The system with nonequilibrium boundary was constructed by joining two bicrystals with tilt boundaries Ɵ = 36.87 ° and Ɵ = 28.07 °, thus the disclination dipole had a strength ω = 8.8 °. The system was relaxed and equilibrated at temperature T=300 K for 200 ps. Then a sinusoidal stress σ = σ0×sin (2πt / τ) with a period τ = 160 ps was applied along x axis at the same temperature and its effect on the structure of the bicrystal was studied. It is shown that under the action of oscillating stresses the nonequilibrium boundary emits lattice dislocations that sink at appropriate surfaces. This process is irreversible and leads to relaxation of the nonequilibrium structure of the boundary. There is an optimal amplitude at which the nonequilibrium boundary emits a sufficient number of dislocations to relieve internal stresses.