To clarify the effect of grain orientation upon the evolution of dislocation structures in metals of medium-to-high stacking fault energy, detailed transmission electron microscopic characterization of structures was carried out for more than 350 individual grains in Al and Cu deformed in tension or by cold rolling up to moderate strain levels (≤0.8). Efforts were made to obtain a precise description of the 3-dimensional arrangement of the dislocation structures and to determine the crystallographic plane of extended dislocation boundaries (geometrically necessary boundaries). A universal pattern of structural evolution characterized by the formation of 3 types of structure was found in both metals, regardless of the material parameters (stacking-fault energy, grain size, impurities) and deformation conditions (mode, strain, strain rate). The key parameter which controlled the formation of the various structural types was found to be the grain orientation with respect to the deformation axis or axes, and a clear relationship between the structural type and the grain orientation was established. A review of single-crystal data revealed a similar relationship. The grain orientation dependence of the structural type, and the similar structural types observed in tension and rolling, suggested a common cause.

Dislocation Structures I - Grain Orientation Dependence. X.Huang, G.Winther: Philosophical Magazine, 2007, 87[33], 5189-214