Evaluation of hot deformation characteristics in modified AA5052 using processing map and activation energy map under deformation heating

The hot workability and deformation characteristics of modified AA5052 were evaluated by hot torsion testing in the temperature range 573-773 K and at strain rates of 0.1-10 s−1. Flow curves obtained from the hot torsion test were corrected considering deformation heating during hot deformation. The processing map and activation energy map were developed from this compensated flow data to propose the optimum processing conditions and to reveal the influence of hot processing parameters on microstructure evolution. The validities of the corrected processing map and activation energy map were also analyzed. The processing map showed that this alloy had a wide flow instability region at all working temperatures; in contrast, maximum power dissipation efficiency was shown at the highest and lowest strain rates in the large temperature region (above 723 K). The activation energy for hot working varied from 28 to 497 kJ mol−1 and showed a tendency for relatively small activation energy where higher power dissipation efficiency was observed. Microstructural observations indicated that dynamic recovery considerably contributed to a higher power dissipation efficiency and lower level of activation energy. On the other hand, the main reason for flow instability was attributed to the evolution of deformation bands or liquid phases. Thus, the hot deformation characteristics of the alloy proposed from the processing map and activation energy map were consistent with the deformed microstructure.