SIZE EFFECTS OF DISLOCATION PATTERNING IN FATIGUED METALS

The finite-size analog of the Walgraef-Aifantis (WA) model of the ''re action + diffusion'' type has been proposed to explain the size effect s of dislocation patterning in fatigued metals. It has been demonstrat ed that the formation of certain patterns can be understood as a resul t of competition between the intrinsic length scales of the WA-model a nd the linear size of the system which can be thought of as grain size , L. In our computer stimulations we demonstrate that depending on the value of grain size L, one can obtain formation of the ladder structu re of persistent slip bands (L = 13 mu m), dislocation grids overlying grain boundaries (L = 1 mu m) or dislocation patterning can become pr ohibited when L --> 0.1 mu m and the system returns to the thermodynam ic branch of solutions.