Mg-RE-Zn-Zr合金的热变形行为和加工图研究

Hot Deformation Behavior and Processing Map of Mg-RE-Zn-Zr Alloy

目的建立Mg-8.5Gd-4.5Y-0.7Zn-0.4Zr合金的本构方程和加工图,得到材料的可加工变形参数。方法采用Gleeble实验机开展温度范围为300~500℃,应变速率范围为0.001~1 s^−1的高温单轴压缩实验。结果流变应力随应变速率的升高和变形温度的降低而增加,当在变形温度为300℃,变形速率为0.1 s^−1和1 s^−1变形时,试样发生了早期开裂;计算得到了合金的变形激活能为228.414 kJ/mol,较高的活化能与LPSO相的存在有关;合金加工图中存在两个可加工区域,第一个区域在变形温度为350~420℃,应变速率为0.001~0.01 s^−1的范围内,第二个区域在变形温度为420~480℃,应变速率为0.005~0.1 s^−1的范围内。结论建立的本构方程得到预测流动应力值与实验值吻合良好,加工图中两个可加工区域的变形机制都为动态再结晶。

The work aims to build the constitutive equation and processing map of Mg–8.5Gd–4.5Y–0.7Zn–0.4Zr alloy to obtain the machined deformation parameters of the material.Uniaxial compression tests at 300℃to 500℃and strain rate ranges from 0.001 s^−1 to 1 s^−1 were conducted with Gleeble-1500D simulated machine.The flow stress increased with the increase of strain rate and the decrease of deformation temperature.When deformed at 300℃at strain rates of 0.1 s−1 and 1 s−1,early failures occurred.The activation energy was calculated to be 228.414 kJ/mol.Such high activation energy can be ascribed to the presence of LPSO phase.There were two feasible processing domains in processing map,the first domain was in the temperature range from 350℃to 420℃and strain rate range from 0.001 s^−1 to 0.01 s^−1,and the second domain was in the temperature range from 420℃to 480℃and strain rate range from 0.005 s^−1 to 0.1 s^−1.The predicted flow stress values obtained through the constitutive equation established were agreed well with the experimental values.The deformation mechanism in two feasible processing domains is dynamic recrystallization.