Microstructure and texture evolution in ECAE processed A5056

Equal channel angular extrusion (ECAE) represents an effective means of microstructural refinement through severe plastic deformation. In aluminum based alloys microstructures obtained by this process generally result in interesting and remarkable combinations of mechanical properties, such as for instance enhanced strength together with high levels of ductility. In the present investigation, the evolution of the tensile properties, microstructures and crystallographic textures during ECAE has been studied for an Al-Mg based workhardening type alloy (A5056) by metallographic observation, transmission electron microscopy (TEM) and X-ray diffraction. The mechanical and microstructural characteristics of these alloys have been compared to extrudates of the same material prepared by conventional extrusion. The results show that dynamic recovery and the development of subgrains, mainly separated from each other by low angle grain boundaries, play an important role with respect to the formation of the ultrafine microstructures observed. No evidence for recrystallization and the nucleation of new grains occured up to pressing temperatures of 300°C and very sharp deformation textures were found to develop. Similar to rolling deformation a transition from a pure metal type texture to an alloy type texture in function of the deformation degree occurs. The formation of these ECAE-textures is discussed on the basis of the Taylor theory of polycrystalline deformation.