AA6013 aluminium alloy deformed by forward-backward rotating die (KoBo): Microstructure and mechanical properties control by changing the die oscillation frequency

The precipitation hardened AA 6013 aluminium alloy was extruded by means of the KoBo extrusion method with an oscillating die. In the presented paper, the influence of two different die rotation frequencies on the microstructure and mechanical properties after KoBo deformation and during post-deformation ageing process is discussed. Initial materials were conventionally hot extruded rods. The extrudates were heat treated to T6 condition and subsequently deformed using the KoBo method, at two frequencies: 2.5 and 8 Hz. The obtained samples were characterised by static tensile tests, scanning and transmission electron microscopy (SEM and TEM), and differential scanning calorimetry (DSC). Electron back scattered diffraction (EBSD) in SEM was applied in order to verify grain size, density of boundaries and local texture. TEM and DSC were used to analyse the influence of plastic deformation on the precipitation process. The results revealed that die oscillation frequency has a great influence on the behaviour of materials during ageing.