ON THE INFLUENCE OF NON-EQUILIBRIUM VACANCIES ON THE CHARACTERISTICS OF STRAIN INDUCED BROKEN DISLOCATION BOUNDARIES

Abstract

The influence of material supersaturation with deformation vacancies on the characteristics of broken dislocation boundaries that appear near wedge disclinations as a result of accommodative plastic deformation is considered. An analysis is made for the elastic and osmotic forces acting on the dislocations of the broken boundary. Using discrete dislocation dynamics method, computer simulation of the nonconservative motion (climb) of dislocations in the boundary plane has been carried out. The broken boundary formed as a result of the splitting of the original disclination into two partial with equal strengths and the boundary with an inhomogeneous distribution of dislocations (with a linearly decreasing misorientation) were considered as initial ones. It is shown that in the case of broken dislocation boundary formed near a positive wedge disclination, dislocation climb leads to its unlimited growth through the model grain with a simultaneous decrease of misorientation. In the case of a boundary formed near a negative disclination, the osmotic forces acting on the dislocations of the broken boundary can, at sufficiently large super saturations of the material with nonequilibrium vacancies, lead to its significant compression with a simultaneous increase of the density of the Burgers vector. In this case, the choice of the initial configuration of the broken boundary has practically no effect on the characteristics of the equilibrium distribution of dislocations. The density distributions of the Burgers vector along the broken boundary are calculated for the case of small and large supersaturations of the material with nonequilibrium vacancies. The critical value of supersaturation above which the boundary compression occurs is calculated. The boundary compression leads to a significant increase in tensile stresses in its vicinity. In this case, the maximum tensile stresses in the plane coinciding with the plane of the boundary are reached at the boundary break point. The results obtained may be of interest in the analysis of possible mechanisms for the initiation of cracks and pores during ductile fracture of metals.