Dislocation Substructure Evolution during Hydrostatic Extrusion of Al Mg Si Alloy

Hydrostatic extrusion is a technique which allows to produce rods with ultra ne grains and unexpectedly enhanced mechanical properties caused by grain re nement. However, the mechanism of such a re nement is not fully understood at this stage. 6xxx aluminium alloys series are usually processed by extrusion. In this study, commercial 6082 aluminium alloy was extruded at ambient temperature in a cooled die in two stages to the true strain of ε = 3.2. Such a processing results in a not fully re ned microstructure which allows to study di erent stages of grain re nement. The texture, dislocation substructures and grain re nement were investigated using electron backscatter di raction and transmission electron microscopy techniques. The results revealed that two main texture components are present in the extruded rods 〈111〉 ber texture and 〈001〉 recrystallized grains. Transmission electron microscopy inspection revealed dislocation structures that can be associated with di erent stages of plastic deformation according to the low energy dislocation structures hypothesis proposed by Kuhlmann-Wilsdorf.