Dislocation Inhomogeneity in Cyclic Deformation

The development of a dislocation inhomogeneity in the form of regular spatial patterns during cyclic deformation is examined from a dynamical instability point of view. A gradient-dependent dislocation dynamics framework is devised and the competition between mobility, interaction, and generation processes is considered. Within such a framework, it is shown that uniform dislocation distributions may become unstable versus spatial modulations leading to the formation of different types of patterns including cellular, ladderlike, and labyrinth structures. In particular, the spatially periodic wall structure of persistent slip bands (PSBs), along with the theoretical determination of the corresponding wavelength, is discussed on the basis of nonlinear dynamical equations of the reaction-diffusion type. The effect of temperature on the wavelength selection process is predicted in accordance with experimental observations. Moreover, it is shown that the possibility of secondary or multiple slip effects and the associated labyrinth structures can conveniently be described by the dynamical model. Finally, a preliminary discussion on the applicability of gradient-dependent disloca­tion dynamics and self-organization techniques, in describing the early stages of the deformation with emphasis on the inhomogeneous development of slip during monotonic loading, is given.