Microtexture and microstructure evolution during processing of pure aluminum by repetitive ECAP

Microtexture and microstructure evolution during repetitive equal-channel angular pressing (ECAP) of pure aluminum through a 90° die was evaluated by orientation imaging microscopy (OIM) and transmission electron microscopy (TEM). Billet distortion appears to conform to the idealized ECAP model. After the initial pass, the textures were inhomogeneous but one or more shear-texture components and long-range lattice rotations were apparent. Following repetitive ECAP, the textures became more homogeneous but still included either two or three distinct shear-texture orientations. The OIM and TEM data revealed meso-scale deformation bands that were inclined at about 26° to the axis of the as-pressed samples and that involved alternation of lattice orientations between distinct shear-texture orientations. The band interfaces were of high disorientation (40–62.8°) and were distinct boundaries in TEM. The evolution of the band structures during repetitive ECAP accounts for an increasing population of high-angle boundaries in repetitively processed materials.