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采用Gleeble-1500热模拟机研究粗晶Mg-6.8Gd-4.5Y-1.1Nd-0.5Zr镁合金在温度为623～803 K、应变速率为0.005～5 s-1条件下的高温变形行为。结果表明:流动应力随变形温度的降低或应变速率的升高而增加,在高温变形初始阶段,流动应力随应变的增加迅速增加,当应变超过一定值后,流变应力开始下降并逐渐趋于稳定,出现稳态流动特征;基于Arrhenius方程建立Mg-6.8Gd-4.5Y-1.1Nd-0.5Zr合金高温流变应力本构模型;在723 K、应变速率0.05 s-1条件下,显微组织出现大晶粒被细小晶粒包围的“项链”组织特征,局部晶粒交结处出现微裂纹与孔洞;根据实验结果,合金的热加工宜在773 K左右进行。
The hot deformation behavior of coarse-grained Mg-6.8Gd-4.5Y-1.1Nd-0.5Zr magnesium alloy at 623 ~ 803 K and strain rate of 0.005 ~ 5 s-1 was investigated by Gleeble-1500 thermal simulator. The results show that the flow stress increases with the decrease of deformation temperature or strain rate. At the initial stage of high temperature deformation, the flow stress increases rapidly with the increase of strain. When the strain exceeds a certain value, the flow stress begins to decrease and gradually approaches Stable and steady-state flow characteristics were observed. Based on the Arrhenius equation, a high-temperature flow stress constitutive model of Mg-6.8Gd-4.5Y-1.1Nd-0.5Zr alloy was established. Under the condition of strain rate of 0.05 s-1 and 723 K, The appearance of “necklace” tissue with large grains surrounded by fine grains appeared microcracks and holes at the local grain junction. According to the experimental results, the hot working of the alloy should be carried out at about 773K.