Effects of strain rate and temperature on hot tensile deformation of severe plastic deformed 6061 aluminum alloy

The hot ductility of severe plastic deformed AA6061 was studied at different temperatures and strain rates. The large processed by ECAP specimens with the dimensions of about 100 mm×100 mm×14 mm were then subjected to cold rolling (CR) in order to fabricate the long Ultra-fine grained sheets. According to microscopic observations and hot tensile tests, the combination of two severe plastic deformations (i.e. ECAP+CR) can affect significantly the refinement of grain/subgrain and the ductility of the studied alloy. The results were then compared with those of as-received and CRed cases. In case of ECAP followed by the cold rolling process, the effect of temperature on the ductility, strain rate sensitivity, activation energy and Zener-Hollomon parameter was higher than strain rate. It can be suggested that the possible mechanism dominated the hot tensile deformation during tensile testing is dynamic recovery and dislocation creep. Although the maximum hot ductility was obtained at 500 °C, an increase in the volume fraction of cavities and their distribution led to a decrease in hot ductility and superplasticity of AA6061 alloy processed by SPD .