Comparative constitutive constants for hot working of Al-4.4Mg-0.7Mn (AA5083)

Torsion tests on as-hot-rolled Al-4.4Mg-0.7Mn alloy were conducted over the strain rate range 0.1 to 10/s and the temperature range 200 to 450 C. As temperature decreased and strain rate increased, the flow curves exhibited peaks that were lower and broader, followed by lower softening, and closer approach to a steady-state regime partly because fracture occurred at higher strains. In constitutive analysis, the power law was found to be inappropriate, but the exponential law was suitable. The hyperbolic sine function was found to fit more closely with stress multipliers between 0.04 and 0.06/MPa. The activation energy was found to be 162 kJ/mol. These results were shown to be in reasonable agreement with previous studies when allowance was made for variations in composition and microstructure. (Author)