Effect of the heat treatment on the hot deformation behaviour of AA6082 alloy

The hot deformation behaviour of AA6082 alloy treated by (a) a T4 temper and (b) annealing, was studied by compression testing over a range of temperature, 300–500 °C, with strain rates of 0.005, 0.05 and 0.09 s−1. It was observed that the flow stresses of the alloy treated by the T4 temper were significantly higher than those of the annealed alloy. Furthermore, the stress–strain curves of the alloy treated by the T4 temper showed significant softening during deformation at the lowest strain rate, while there was no significant softening of the alloy treated by annealing under any of the deformation conditions. The activation energy for hot deformation was determined for different strains, using a power law equation, and was found to change significantly with strain for the alloy treated by the T4 temper. The stress–strain data calculated from a power law equation, with strain dependant parameters, show a very good fit with the experimental data for the alloy treated by the T4 temper. This phenomenon was explained by the occurrence of dynamic precipitation and coarsening during deformation.