ON THE DISLOCATION DYNAMICS OF PERSISTENT SLIP BANDS IN CYCLICALLY DEFORMED FCC METALS

A dislocation dynamical description is presented of the plastic strain localization and the mesoscopic dislocation patterning associated wit h persistent slip bands (PSBs) in fatigued face-centred cubic (f.c.c.) metals. The analysis focuses on the densities and the height distribu tions of edge dislocation dipoles formed in cyclic stress saturation. The following dislocation mechanisms are assumed to govern the operati on of a PSB: (i) glide-induced dipole decomposition is important for e stablishing steady-state conditions in cyclic saturation, (ii) small p ile-ups of three to four edge dislocations induce yielding of the PSB walls. When these processes are taken into account, quantitative agree ment is achieved with recent experimental observations on Ni single cr ystals fatigued in the temperature range from 77 to 750 K. (C) 1998 Ac ta Metallurgica Inc. Published by Elsevier Science Ltd. All rights res erved.