预孪晶AQ80镁合金热压缩本构方程及热加工图

Constitutive equation and processing map of hot deformation for pre-twin AQ80 magnesium alloy

采用Gleeble-3500热模拟试验机,对预孪晶AQ80镁合金在变形温度为250~400℃、应变速率为1×10^(-3)~5 s^(-1)条件下进行热压缩实验。预孪晶AQ80镁合金本构方程的建立通过Arrhenius双曲正弦函数推导而来。基于动态材料模型,建立在应变量为0.1、0.3和0.5下的热加工图。结果表明:预孪晶AQ80镁合金的流变应力随着变形温度升高和应变速率下降而减小,热加工图中耗散峰值(η=48%)区出现在低温低应变速率范围(250~280℃,1×10^(-3) s^(-1))。结合热加工图和其对应区域的金相组织进行分析得出:应变量为0.5的失稳区在温度为250~400℃、应变速率为0.1~5 s^(-1)范围内;然而,加工安全区在温度为300~400℃、应变速率在1×10^(-3)~1×10^(-2) s^(-1)范围内,组织特征表现为动态再结晶。

The hot compression tests of pre-twin AQ80 magnesium alloy were conducted at temperature of 250-400℃and strain rates of 1×10-3 to 5 s-1 by using the Gleeble-3500 hot-simulator.The constitutive equation of pre-twin AQ80magnesium alloy was constructed by Arrhenius hyperbolic sine function.According to dynamic materials model,the hot processing maps of pre-twin AQ80 magnesium alloy were established for strain of 0.1,0.3 and 0.5.The results show that the flow stress of pre-twin AQ80 magnesium alloy decreases with the decrease of strain rate and the increase of temperature.The processing maps exhibit one peakηvalue（48%）region at temperature of 250-280℃and the strain rate of 1×10-3 s-1.Combining with analysis of hot processing map and the corresponding microstructure at each domain,the instability regions were identified to be at the temperature range of 250-400℃and strain rate of 0.1-5 s-1 for billets deformed to strains of 0.5,while the microstructures characteristic mainly show dynamic recrystallization at the temperature of 300-400℃and strain rate of 1×10-3-1×10-2 s-1,which were indicated as safe regions.