Computer simulations of Orowan process controlled dislocation glide in particle arrangements of various randomness

Orowan process controlled dislocation glide in single crystals containing spherical precipitates is computer simulated. The critical resolved shear stress (CRSS) is derived. The simulations are based on the equilibrium of resolved stresses in one glide plane. The elastic dislocation self stress is fully taken into account. The particle radii distribution is that of an Ostwald-ripened crystal. Particle arrangements in space with different degrees of randomness in their nearest neighbor spacings have been computer generated. An experimentally accessible parameter Z, 0less than or equal toZless than or equal to1, is introduced which describes this randomness. Computer generated arrangements are compared with micrographs of a real specimen taken from scanning electron microscopy and atomic force microscopy. The investigated specimen is described well by Z = 0.55. The dependence of the CRSS on the particle volume fraction, the mean particle radius and on Z is calculated by simulations. From uniform particle arrangements (Z = 0) to random ones (Z = 1). the CRSS decreases linearly by 20%. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.