(1. 哈尔滨理工大学材料科学与工程学院，哈尔滨 150080；
2. 黑龙江科技大学材料科学与工程学院，哈尔滨 150022；
3. 哈尔滨焊接研究院有限公司，哈尔滨 150028)
摘 要: 采用Gleeble-3800型热模拟试验机对挤压铸造态AZ91D镁合金进行了热压缩实验，研究在温度250~400 ℃、应变速率0.001~1 s-1条件下挤压铸造态AZ91D镁合金的流变应力行为，同时利用金相分析(OM)、透射分析(TEM)和电子背散射分析(EBSD)对其变形微观组织进行了研究，建立其本构方程和热加工图。结果表明：应变速率和温度对挤压铸造态AZ91D镁合金的流变应力行为有显著的影响；挤压铸造态AZ91D镁合金最合适的加工范围是360~400 ℃、0.001~1 s-1与270~360 ℃、0.001~0.01 s-1；在应变速率0.1 s-1的条件下，随着温度升高，动态再结晶起始的临界应变由0.11降至0.02，形变孪晶与位错逐渐被动态再结晶取代，挤压铸造态AZ91D镁合金的变形机制由滑移和孪生转向滑移与动态再结晶相协调。
关键字: AZ91D镁合金；流变应力；动态再结晶
（1. School of Materials Science and Engineering, Harbin University
of Science and Technology,Harbin 150080,China;
2. School of Materials Science and Engineering,
Heilongjiang University of Science and Technology, Harbin 150022, China;
3. Harbin Welding Institute Limited Company,
Harbin 150028, China）
Abstract:The flow stress behavior of squeeze-cast AZ91D alloy was studied using thermal simulation tests on a Gleeble-3800 machine at the temperature range of 250-400 ℃ and strain rate of 0.001-1 s-1. The microstructure was investigated by using optical microscopy (OM), transmission electron microscopy (TEM) and electron back scatter diffractometry (EBSD), and the constitutive equation and thermal processing map of the Squeeze-cast AZ91D alloy was established. The results show that the effect of strain rate and temperature on the flow stress behavior is significant. The thermal processing map exhibits that the suitable processing conditions as follows: 360-400 ℃, 0.001-1 s-1 and 270-360 ℃, 0.001-0.01 s-1. The critical strain for the initiation of dynamic recrystallization decreases from 0.11 to 0.02 with the increase of temperature at 0.1 s-1. The deformation twins and dislocations are gradually replaced by dynamically recrystallized grains. The deformation mechanism of squeeze cast AZ91D magnesium alloy changes from slip and twinning to the coordination of slip and dynamic recrystallization.
Key words: AZ91D magnesium alloy; flow stress; dynamic recrystallization
