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 PO s(-1) and the temperature range 200 to 450 deg reesC. As temperature decreased and strain rate increased, the flow curves exhibited peaks that were tower and broader, followed by lower softening, a nd closer approach to a steady-state regime partly because fracture occurre d at higher strains. In constitutive analysis, the power law was found to b e 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-1. The activation energy was found to be 162 kJ/mol. These re sults were shown to be in reasonable agreement with previous studies when a llowance was made for variations in composition and microstructure.