The interactions between dislocations and dislocation dipoles

Abstract

The actual movements of dislocations approaching a dislocation dipole under an applied stress were calculated numerically, assuming that the velocity of each dislocation involved is proportional to the total force exerted by the applied stress and the stresses produced by the other dislocations. The resultant end products for all starting conditions of various configurations containing up to four dislocations were determined. It was found that starting conditions resulting in equilibrium positions for all dislocations are much less numerous than previously assumed. In fact it was found that decomposition of the dipole occurs usually more often than trapping of the approaching dislocations. This results in a pronounced instability of dipoles under an applied stress against the injection of a few free dislocations. This fact may be used to explain experimentally observed indications of slip instabilities like coarse slip steps and strain bursts in cyclically deformed metals.