(湖南大学 材料科学与工程学院, 长沙 410082)
摘 要: 在应变速率为0.005～5 s-1、 变形温度为250～450 ℃条件下， 在Gleeble-1500热模拟机上对AZ31镁合金的高温热压缩变形特性进行了研究。结果表明： 材料流变应力行为和显微组织强烈受到变形温度的影响； 变形温度低于350 ℃时， 流变应力呈现幂指数关系； 变形温度高于350 ℃时， 流变应力呈现指数关系； 变形过程中发生了动态再结晶且晶粒平均尺寸随变形参数的不同而改变，其自然对数与Zener-Hollomon（Z）参数的自然对数成线性关系；材料动态再结晶机制受变形机制的影响， 随温度的不同而改变； 低温下基面滑移和机械孪晶协调变形导致动态再结晶晶粒的产生； 中温时Friedel-Escaig机理下位错的交滑移控制动态再结晶形核； 高温时位错攀移控制整个动态再结晶过程。 在本实验下， 材料的最佳工艺条件是：变形温度350～400 ℃， 应变速率为0.5～5 s-1。
关键字: AZ31镁合金； 热压缩变形； 微观组织； 动态再结晶
AZ31 magnesium alloy at elevated temperature
（ School of Materials Science and Engineering,
Hunan University, Changsha 410082, China）
Abstract: Hot compression tests of AZ31 magnesium alloy were performed on Gleeble 1500 at strain rates ranged in 0.005-5 s-1 and deformation temperature 250-450 ℃. The results show that the flow stress behaviors and microstructures strongly depend on the deformation temperature. The relationship between flow stress and deformation temperature as well as strain rate can be represented by the exponential equation during temperature below 350 ℃, and by the power equation during temperature over 350 ℃. Dynamic recrystallization (DRX) takes place during the deformation process, and the average dynamically recrystallized grain size(drec) changes with deformation variables. The natural logarithm of drec is linear with the natural logarithm of Zener-Hollomon（Z）parameter. The mechanisms of DRX depend on the deformation mechanisms and change with temperature. Low-temperature DRX is associated with the operation of basal slip and twinning. At intermediate temperatures, cross-slip of α dislocations by Friedel-Escaig mechanism controls the nucleation of DRX. At high temperatures, the operating DRX mechanisms is controlled by dislocation climb. In the present work the good deformation condition is temperature of 350~400 ℃ with stain rate of 0.5-5 s-1.
Key words: AZ31 magnesium alloy; hot compression deformation; microstructure; dynamic recrystallization
