The Microstructure and Properties of Hydrostatically Extruded Polycrystalline Aluminium Al99.5 / Mikrostruktura I Własności Wyciskanego Hydrostatycznie Polikrystalicznego Aluminium Al99.5

The changes of Al99.5 microstructure and properties deformed by hydrostatic extrusion process in the conditions of constant strain rate (1.35×10 2 s -1 ) and variable deformation ( φ = 1.44÷2.85) were investigated. The samples were investigated by means both optical (LM) and transmission electron microscopy (TEM). The size of subgrain was statistically measured by mean chord. To establish the influence of hydrostatic extrusion on the properties of the polycrystalline aluminium Al99.5, the microhardness was measured and the tensile test was performed. The bands and shear bands were the characteristic feature of the sample microstructure. TEM micrographs show equiaxed subgrains with small density of dislocations inside. The measured subgrain size was placed in the range of d = 550÷650 nm. The mechanical properties of polycrystalline aluminium Al99.5 keep almost the same level in the investigated range of deformations. It was found that after the initial deformation microhardness and yield stress nearly twice increase in comparison to the initial state. The greatest increase of properties was observed after deformation φ = 1.44. Then the mechanical properties stabilize.