Tensile ductility of extruded aluminium alloy AA6063 in different tempers

Abstract

The tensile ductility of the extruded aluminium alloy AA6063 in different tempers is investigated experimentally in this study. The results are correlated with the microstructure and the anisotropic plasticity of this alloy, previously investigated in Khadyko et al. (2017) [1]. To this end, uniaxial tensile specimens were produced from an extruded flat profile at different angles to the extrusion axis. The specimens were tested in the naturally aged (T1) condition and after heat-treatment to the peak-aged (T6), over-aged (T7) and soft annealed (O) conditions. The crystallographic texture, the precipitate content, the precipitate free zones around grain boundaries and the primary particle content were characterized prior to testing. Digital image correlation was used to measure the in-plane surface deformation and calculate strain fields during the tensile tests until fracture. The fracture surfaces were investigated in the scanning electron microscope to study the dimple structure. The tensile test results show that the tensile ductility decreases linearly with increasing tensile strength and varies markedly with the tensile direction. The tensile ductility exhibits similar directional dependency as the plastic strain ratio with some deviations around the extrusion axis, which are attributed to the anisotropy of the flow stress. The results indicate that the variation of the tensile ductility with loading direction is controlled mostly by the plastic anisotropy of the material and less by other microstructural features.