铸态Mg-8Y-6Gd-1Nd-0.17Zn稀土镁合金高温压缩本构行为及加工图

Constitutive Behavior and Processing Map of As-cast Mg-8Y-6Gd-1Nd-0.17Zn Magnesium Alloy Com-pressed At Elevated Temperature

摘要:

研究了铸态Mg-8Y-6Gd-1Nd-0.17Zn镁合金在应变量为50%、温度350℃~450℃、应变速率0.0001s-1~0.1s-1的范围内热压缩过程中的本构行为、组织演变和热加工性能。通过选用双曲正弦本构方程来描述合金的流变行为以及变形参数间的关系。实验结果表明，温度和应变速率对Mg-8Y-6Gd-1Nd-0.17Zn镁合金的流变应力行为有重要影响，其流变应力随温度的降低和应变速率的增加而增大，并且在温度高于400℃压缩时，合金的真应力应变曲线具有典型的动态再结晶特性。在本实验条件下，该合金变形期间的活化能（Q）和应力指数（n）分别为359.258 KJ / mol 和5.24，实验值与计算值之间的平均误差（ARE）为3.37％。最后基于动态材料模型加工理论，结合热加工图和压缩过程中的组织演变，确定了该合金的最佳热加工参数为：加热温度400~450℃，应变速率为0.0001s-1~0.001s-1。

Abstract:

The constitutive behavior and hot workability of as-cast Mg-8Y-6Gd-1Nd-0.17Zn magnesium alloy during the hot compression were investigated at elevated temperature (350 °C ~ 450 °C) and different strain rates (0.0001 s?1~0.1 s?1) under the ultimate compression ratio of 50%. The relationship among these deformation parameters of Mg-8Y-6Gd-1Nd-0.17Zn alloy could be adequately characterized by a sine hyperbolic equation. The experimental results show that both temperature and strain rate have important effects on the flow stress behavior of Mg-8Y-6Gd-1Nd-0.17Zn magnesium alloy, and the flow stress increased with lower temperature and higher strain rates. Typical dynamic recrystallization character is found in the true stress-strain curves when samples compressed above the temperature of 400 ℃. The activation energy (Q) and stress exponent (n) during deformation were 359.258 kJ/mol and 5.24, respectively. The average error (ARE) between experimental and calculated values is 3.37%. Then, the processing map was also established and analyzed based on dynamic material model. Considering the processing map and microstructures observation, the optimum hot-working parameters of the alloy were determined to be at a temperature of 400 °C ~ 450 °C and a strain rate of 0.0001 s-1 ~ 0.001 s-1.