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 \(\langle {111}\rangle \) and \(\langle {110}\rangle \). 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 \(\langle {110}\rangle \) starting orientation features an average grain size value of 150% higher than the second investigated single crystal (\(0.5\ \upmu \hbox {m}\) for the \(\langle {111}\rangle \) single crystal and \(1.3\ \upmu \hbox {m}\) for the second crystal). In turn, the average grain size obtained for polycrystalline aluminium is \(0.9\ \upmu \hbox {m}\). 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.