Evolution of dislocation line shape in multicomponent alloys under loading

Abstract

The evolution of the dislocation line shape in a multicomponent alloy CrCoNiFeMn under loading was investigated by the method of discrete dislocation dynamics. It was found in a numerical experiment that the best approximation for the shape of the average bulge of the dislocation line would be a sinusoidal shape rather than a parabolic or arc shape. The equilibrium form of dislocation at zero load fits well into a band with a width of three correlation lengths of the short-wave component of the shear stress field created by dissolved atoms in the glide plane. In this case the dislocation line waviness on the scale of the correlation length of the long-wave component is not observed. It has been found that dislocation segments can overcome internal stress barriers with external applied stress assistance. This is an irreversible process of new equilibrium bulges formation. One of these bulges becomes nonequilibrium, increases and releases the dislocation from the initial fixation at a critical stress, which can be conditionally considered to be the yield strength. The external stress, which assists to the dislocation segments to overcome the internal stress barriers, can to some extent compensate for the short-wave component of the shear stress field. Then, as the numerical experiment shows, the dislocation line waviness on the scale of the correlation length of the long-wave component will be activated. Thus, the two components of the shear stress field affect the shape of the dislocation line separately and sequentially with increasing external load. Keywords: shear stresses, solid solution, glide plane, dislocation.