Deformation-induced long-range internal stresses and lattice plane misorientations and the role of geometrically necessary dislocations

H Mughrabi (1)

1 Inst Werkstoffwissenschaften, Lehrstuhl 1

The goal of this study is to develop a general picture of the role of geometrically necessary dislocations (GNDs) in the evolution of long-range internal stresses and lattice plane misorientations in the heterogeneous dislocation pattern of deformed crystals. For this purpose, X-ray diffraction techniques are considered as the pertinent experimental tools. On the modelling side, the composite models of single/multiple slip serve to interpret the experimentally measured long-range internal stresses quantitatively in terms of densities of GNDs. However, in order to be able to deduce from experiment the evolution of those GNDs that are responsible for the observed lattice plane misorientations, the composite model must be refined. Quite generally, one and the same GND array can give rise to both long-range internal stresses and lattice plane misorientations. On this basis, available experimental data obtained on cyclically and tensile-deformed copper single crystals were analyzed quantitatively. The stresses acting locally in the “hard” dislocation cell walls and in the “soft” cell interiors and the magnitude of the internal stresses are found to increase approximately linearly with the applied stress. The density of the GNDs responsible for the long-range internal stresses (and/or for the misorientations) is always found to amount to only a few per cent of the total dislocation density. An analysis of the evolution of the lattice plane misorientations shows that the kink walls and the dislocation sheets/grids in stage II are geometrically necessary boundaries (GNBs), whereas the dislocation cell walls formed by multiple slip are incidental dislocation boundaries (IDBs).

Mots clés: Physical Sciences

H Mughrabi. Deformation-induced long-range internal stresses and lattice plane misorientations and the role of geometrically necessary dislocations. Philosophical Magazine, 2006, 86 (25-26), pp.4037-4054. ⟨10.1080/14786430500509054⟩. ⟨hal-00513649⟩