HETEROGENEOUS MICROSTRUCTURES AND MICROTEXTURES IN CUBE-ORIENTED AL CRYSTALS AFTER CHANNEL DIE COMPRESSION

Pure aluminum crystals of cube orientation have been deformed in plane -strain compression to strains of unity using a channel die. The macro structures and microstructures were characterized in three dimensions by a range of metallographic techniques including optical, scanning, a nd transmission electron microscopy. Particular attention was paid to quantifying global textures and local variations in crystal orientatio n by means of X-ray pole figures, automatic electron back-scattered di ffraction (EBSD) and semiautomatic transmission electron microscope (T EM) Kikuchi line analysis. Cube crystals are observed to break up into macroscopic deformation bands aligned along the elongation direction and strongly disorientated by rotations mostly, but not uniquely, abou t the transverse direction. The bands develop deformation substructure s of dislocation boundaries or, in certain cases, of intersecting disl ocation boundaries which have characteristic microtexture signatures o f alternating lattice rotations. The transition regions between the ba nds are composed of equiaxed dislocation cells which accommodate conti nuous orientation gradients over distances of about 20 mu m. Compared to the behavior of rolled Al crystals, the macroscopic bands are obser ved to lie in different planes, but the microscopic subdivisions and m icrotextures developed in the channel die and in rolling are very simi lar. The origins of the macroscopic and microscopic subdivisions are d iscussed in terms of the local deformation modes and slip amplitudes a nd their relation to the behavior of rolled crystals.