A Comparative Study on Constitutive Models for High Strength Aluminum Alloy AA7075 Flow Behavior in Hot Stamping

Abstract:

In hot stamping, the high strength aluminum alloy AA7075 blank was first fully solutionized and then transferred into room temperature tools, stamped and quenched. To characterize the AA7075 alloy hot deformation behavior, tensile tests employing the heating path representative of the hot stamping process were performed over the temperature range of 200-480 °C and strain rate range of 0.01-10 s_-1. Modified constitutive models based on the Arrhenius type model, Johnson-Cook model and Zerilli-Armstrong model were proposed and calibrated with the hot tensile test data. The proposed models coupled the strain, strain rate and temperature effects on flow stress by expressing the model parameters as polynomial functions of strain, strain rate and temperature. The prediction accuracy of the constitutive models on flow stress was evaluated by the mean square error (MSE) and the correlation coefficient R value. The results indicated that the modified Johnson-Cook model can provide most accurate prediction for the AA7075 hot flow behavior.