Microstructure and texture development in a polycrystal and different aluminium single crystals subjected to hydrostatic extrusion

Abstract

A hydrostatic extrusion (HE) process was applied to commercial pure polycrystalline aluminium (99.9%) and two aluminium single crystals (111) and (110). On comparison, the results obtained from single crystals and polycrystalline aggregates are unique. Microstructure and crystallographic texture investigations were performed by transmission electron microscopy, electron backscatter diffraction and X-ray diffraction (XRD). Significant differences in grain refinement and texture formation were noticed depending on the starting orientation. The deformed single crystal with (110) starting orientation features an average grain size value of 150% higher than the second investigated single crystal (0.5 Μm for the (111) single crystal and 1.3 Μm for the second crystal). In turn, the average grain size obtained for polycrystalline aluminium is 0.9 Μm. The deformation process causes a difference in the grain sizes, while a fraction of the high angle grain boundaries have a comparable volume percentage in all the deformed microstructures-reached about 35%. The qualitative and quantitative XRD texture results proved that the HE process leads to the formation of a characteristic fibrous texture.