镁合金挤压-剪切变形行为的物理和数值模拟研究

Physical and Numerical Simulation of Deformation Behaviors of Extrusion-Shear for Magnesium Alloy

提出了基于热模拟仪的镁合金挤压-一次剪切(extrusion-shear)二步复合制备工艺(简称ES工艺),设计并制造了适合于热模拟仪Gleeble1500D的ES热物理模拟装置,进行了热模拟实验,建立了基于DEFORM软件的ES挤压有限元数值模型,并进行了有限元模拟。研究了坯料变形过程的应变率、挤压力、应变-应力等物理量。从ES热物理模拟和数值模拟过程的挤压力、应变-应力曲线的特点,发现ES工艺中镁合金发生了特有的动态再结晶过程,具有明显的两个动态再结晶阶段,被称为"双级动态再结晶"。镁合金坯料的等效应变率在正挤压阶段,累积应变的值较小,发生了少量的动态再结晶,在经过一次剪切后等效应变率急速上升,发生了第二阶段的动态再结晶,镁合金坯料的微观组织经过挤压-剪切逐步细化。

A new composite extrusion method of Mg alloys was proposed which combined extrusion and one-time shear （ES）. ES devices suitable for the thermal simulation instrument Gleeble1500D were designed and made and the theoretical simulation experiments were conducted. ES thermal-mechanical coupled finite element models were established based on the commercial DEFORM TM -3D software for FE simulation. The strain rate, extrusion force and stress-strain of the billet were studied during the deformation process. A new recrystallization mode has been discovered, which is different from the traditional recrystallization process and known as the ＂double-stage dynamic recrystallization＂. In the extrusion stage, the accumulation strain value is smaller, and a little dynamic recrystallization happens. However, the equivalent strain rate of magnesium alloy billets after one-time shear rises rapidly, and the second phase of more dynamic recrystallization occurs. Microstructures of magnesium alloy billets are gradually refined after two phases dynamic recrystallization.