挤压态镁合金流变行为及本构模型研究

Study on the flow behavior and constitutive model of extruded magnesium alloy

通过Gleeble热模拟机,在变形温度250~500℃、应变速率0.005~5 s-1下对挤压态镁合金进行热压缩实验,得到应力-应变曲线,基于加工硬化与软化机制,分析了温度和应变速率对流变曲线及峰值应力的影响。其次,考虑变形中温升,在高应变速率下采用温度补偿修正流变应力。最后,运用双曲正弦模型构建不同流变应力范围的本构模型,得到流变应力与温度、应变速率和应变的定量关系。将模型预测应力值与实验值进行对比。结果表明:实验值与预测值的相关性系数为0.984,平均相对误差绝对值为3.87%,说明所建立的本构模型能够准确预测成形过程中不同变形量下镁合金的流变应力值。

Hot compression tests were conducted on Gleeble thermal simulator at deformation temperature from 250 ℃ to 500 ℃ and strain rate from 0. 005 s-1 to 5 s-1 for extruded magnesium alloy. The corresponding stress-strain curves were obtained. Based on strain hardening and softening mechanism,influences of temperature and strain rate on the flow curve and peak stress were analyzed. Considering the temperature rise during deformation,flow stresses were corrected with temperature compensation at high strain rate. Finally,constitutive model with different flow stress range was constructed by hyperbolic sine model. The quantitative relationship of flow stress with strain rate,strain,temperature were obtained respectively. The predicted values were compared with the experimental values. Results show that correlation coefficient of the flow stress between the experimental value and the predicted value is up to 0. 984,and the average relative error is 3. 87%,which indicate that the established constitutive model can be used to predict the flow stress of magnesium alloy under different deformations in the forming process.