Development of an Al 7050-10 vol.% alumina nanocomposite through cold consolidation of particles by high-pressure torsion

An Al 7050-10 vol.% Al2O3 nanocomposite was produced by cold consolidation of Al 7050 gas-atomized powder with alumina particles by means of severe plastic deformation using high-pressure torsion (HPT). The processing was conducted at room temperature under a pressure of 6.0 GPa, for 50 revolutions with a rotation speed of 2 rpm. The purpose of this work was to consolidate at room temperature one high strength Al alloy with Al2O3 particles without any prior or post sintering. In order to characterize the product, the disk microstructure was examined after consolidation using scanning and transmission electron microscopy and X-ray diffraction was used to determine the presence of different phases. Energy-dispersive X-ray spectroscopy (EDS) was undertaken to provide chemical analysis of the phases and hardness tests were performed to check the strength. The results show that the alumina particles in the periphery of the disk are more finely dispersed than in the central regions. The average grain size of the Al 7050 matrix ranged from ∼50 to ∼200 nm and the hardness measurements varied from ∼237 Hv to ∼307 Hv with disk edges having higher hardness values than in the central area.