Formation mechanisms of cyclic saturation dislocation patterns in [001], [011] and [(1)over-bar 1 1] copper single crystals

This work reveals the formation mechanisms of saturation dislocation patterns in three typical multiple-slip oriented [0 0 1], [0 1 1] and [(1) over bar 1 1] copper single crystals. Compared with the single-slip oriented copper single crystals, the three multiple-slip oriented ones show very different dislocation patterns. It was found that the dislocation patterns in cyclically saturated copper single crystals are the Labyrinth structure for [0 0 1], wall structure for [0 1 1] and cell structure for [(1) over bar 1 1] , respectively. Based on a two-phase structure consisting of persistent slip bands and veins for single-slip orientation, the formation mechanisms of the dislocation patterns in multiple-slip oriented crystals are proposed as follows: the formation of the complex dislocation patterns depends on the activating slip system. The easy operation of the critical secondary slip system will contribute to the formation of the Labyrinth structure. The activation of the coplanar secondary slip system will be beneficial to formation of the cell structure. If no secondary slip system is activated, the wall structure is more prone to appear. Finally, the intrinsic relationship between various dislocation patterns and face centered cubic crystal structure was established. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.