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 Compressed at Elevated Temperatures

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0.0001~0.1 s^-1条件下热压缩过程中的本构行为、组织演变和热加工性能。选用双曲正弦本构方程描述合金的流变行为以及变形参数间的关系。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 k J/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0.0001~0.001 s^-1。

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(350~450℃)and different strain rates(0.0001~0.1 s^−1)under the ultimate compression ratio of 50%.The relationship among these deformation parameters of Mg-8Y-6Gd-1Nd-0.17Zn alloy was 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 increases at lower temperature and higher strain rates.Typical dynamic recrystallization character is found in the true stress-strain curves when samples are compressed at the temperature above 400℃.The activation energy(Q)and stress exponent(n)during deformation are 359.258 kJ/mol and 5.24,respectively.The average error(ARE)between experimental and calculated values is 3.37%.Then,the processing maps are also established and analyzed based on dynamic material model.Considering the processing maps and microstructure observation,the optimum hot-working parameters of the alloy are determined to be temperatures of 400~450℃ and strain rates of 0.0001~0.001 s^-1.