AZ91镁合金高温变形本构关系

CONSTITUTIVE RELATIONSHIP OF HOT DEFORMATION OF AZ91 MAGNESIUM ALLOY

采用Gleeble-1500热模拟机对AZ91镁合金进行了高温压缩变形实验,分析了该合金在变形温度为250—400℃、应变速率为0.001—1 s^(-1)条件下流变应力的变化规律.结果表明,变形温度和应变速率均对流变应力有显著的影响,流变应力随变形温度的升高和应变速率的降低而降低,当变形温度≥400℃、应变速率≤0.001 s^(-1)时,流变应力随变形量的增加达峰值后呈稳态流变特征.并采用双曲正弦模型确定了该合金的变形激活能Q和应力指数n随应变量的变化规律,建立了相应的热变形本构关系.经实验验证,所建立的本构关系能较好地反映AZ91镁合金实际热变形行为特征.

Hot compression deformation of AZ91 magnesium alloy has been performed on Gleeble-1500 under conditions of strain rates of 0.001—1 s^-1 and deformation temperatures of 250—400℃,and the flow stresses in different deformation conditions are investigated.The results show that the flow stress is significantly affected by both deformation temperature and strain rate,the flow stress decreases with the deformation temperature increasing and strain rate decreasing.The flow stress tends to be constant after a peak value at deformation temperature higher than 400℃and strain rates less than 0.001 s^-1.The relations of the deformation activation energy and stress exponent with strain were obtained using the hyperbolic-sine mathematics model,and the hot deformation constitutive relationship was established.Comparing with experimental results,it is proved that the model reflects the real deformation feature of the AZ91 alloy.