Ultrasound influence on behavior of disordered dislocation systems in a crystal with non-equilibrium grain boundaries

D.V. Bachurin, R.T. Murzaev, J.A. Baimova, A.A. Samigullina, K.A. Krylova show affiliations and emails
Received 01 July 2016; Accepted 19 August 2016;
This paper is written in Russian
Citation: D.V. Bachurin, R.T. Murzaev, J.A. Baimova, A.A. Samigullina, K.A. Krylova. Ultrasound influence on behavior of disordered dislocation systems in a crystal with non-equilibrium grain boundaries. Lett. Mater., 2016, 6(3) 183-188
BibTex   https://doi.org/10.22226/2410-3535-2016-3-183-188
This paper presents a numerical simulation of behavior of disordered dislocation systems under ultrasound influence in a model grain of two-dimensional polycrystal containing non-equilibrium grain boundaries. Non-equilibrium state is modeled via the stress field of wedge junction disclination quadrupole, which is a characteristic element of non-equilibrium structure of ultra-fine grained materials obtained by severe plastic deformation methods. It is assumed that the length of a standing sound wave is much larger than oscillation amplitude of the dislocations, and stress amplitude is below the dynamic yield stress. Dislocation positions and the sign of their Burgers vectors in the initial configuration are set randomly. All dislocations belong to the same slip system, but locate on different (parallel) glide planes. Qualitatively different behavior of the dislocation structures in contrast to the infinite crystal was found. Namely, no dislocation walls with alternating sign of the Burgers vector was found. Instead of this, if the number of dislocations is small, practically all dislocations move from the grain into the boundaries. Formation of a substructure consisting of dislocation walls, dipoles and multipoles occurs at higher dislocation densities. More pronounced "cleaning" of the grain from the dislocations takes place at increased amplitudes of ultrasonic influence. For quantitative assessment of relaxation of dislocation system, the trace of the internal stress tensor is calculated. The presence of two (fast and slow) relaxation stages was revealed. It is shown that the level of internal stresses, associated with the restructuring of disordered dislocation structure, can be reduced up to 20%.