AA7075高强铝合金热冲压流变行为本构模型对比研究

在热冲压过程中,AA7075高强铝合金板料经充分固溶后移入室温模具进行冲压成形并淬火。为表征AA7075铝合金在热冲压工艺中的变形行为,在温度200~480℃、应变速率0.01~10s-1范围内进行了高温拉伸试验。基于Arrhenius类型本构模型、Johnson-Cook模型以及Zerilli-Armstrong模型提出了多种修正本构模型,并应用实验所获流变曲线进行了拟合。提出的修正模型通过将模型参数表示为应变、应变速率及温度相关的多项式函数耦合了应变、应变速率及温度对流变应力的影响,并通过均方误差(MSE)以及相关系数R值对模型流变应力预测准确性进行了评价。结果表明,修正的Johnson-Cook模型能够更加准确的预测AA7075高温流变行为。

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

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.