Constitutive modeling and inverse analysis of the flow stress evolution during high temperature compression of a new ZE20 magnesium alloy for extrusion applications

The high temperature deformation behavior of a new magnesium alloy, ZE20 (Mg-2.4%Zn-0.2%Ce), using uniaxial isothermal compression testing, is investigated within the paper. A set of experiments was conducted at temperatures of 350-425 degrees C, and strain rates in the range of 0.01 s(-1) to 10 s(-1), and samples were compressed by 70% of their original length. An inverse analysis approach was used to evaluate flow stress curves based on load displacement measurements for each deformation condition. Flow stress evolution for the new alloy under these test conditions showed higher flow stress and lower work softening than commercially available magnesium casting alloys. Finally, constitutive equations predicting flow stress as a function of strain, strain rate, and temperature were applied to modeling mechanical response of the new alloy. Predictions from three constitutive models of steady state stress were validated against uniaxial compression data. It was found that all three models evaluated reliably predict the high strain stress values to within 15% of measured values.