Effect of alloy composition on hot deformation behavior of some Al-Mg-Si alloys

Abstract

The hot flow stress behavior of three Al-Mg-Si alloys was determined by performing hot deformation compression tests on a Gleeble 3500 thermomechanical simulator over the temperature range 400 °C–550 °C and at strain rates from 0.01 s−1 to 10 s−1. Using the hyperbolic sine constitutive model, constitutive parameters for prediction of the hot flow stress behavior of these different alloys were determined. The effect of chromium (Cr) addition and increased Mg-Si content on the average steady flow stress, constitutive and strain rate sensitivity (m) parameters was determined. For deformation at low strain rates (0.01–1s−1), the alloy containing 0.2 wt % Cr exhibited higher average steady flow stress than the alloy with similar Mg-Si content and no Cr addition. The addition of 0.2 wt % Cr and an increase in Mg-Si content were observed to result in a decrease of the strain rate sensitivity parameter (m) and an increase in the activation energy for hot deformation. The predictive accuracy of the developed models was demonstrated by comparing the predicted and experimental flow stress behavior of alloy 3 at deformation conditions different from the temperature and strain rate conditions used to develop the models parameters. Results indicate that the developed model can accurately predict the alloy behavior at strain rate and temperature conditions beyond the range of model development.