AZ80镁合金热挤压织构的多晶体建模

摘要

为合理模拟 AZ80镁合金的热挤压织构，在粘塑性自洽(VPSC)多晶体塑性框架中实现了动态再结晶织构的模拟。基于此模型，考察了挤压温度和挤压边界条件对 AZ80镁合金挤压织构的影响，模拟所得结果与实验结果有较好的吻合。模拟结果表明：新的大角度界面(HABs)的形成使再结晶晶粒与母晶之间形成取向差，再结晶晶粒因此偏离母晶形成了{2110}纤维织构组分。此外，因为基面〈a〉滑移具有更低的滑移抗力并易于开动，当垂直于挤压轴方向上加载的应变不再轴对称时，晶粒的基面总倾向于转向加载应变更多的方向以便于基面〈a〉滑移承载更多的塑性变形。挤压温度的升高有利于锥面〈c+a〉滑移的开动并使再结晶体积分数增多，在一定程度上弱化了挤压形成的基面织构。%The visco-plastic self-consistent (VPSC) model is extended to take the dynamical recrystallization (DRX) into account so that the hot extrusion texture of AZ80 magnesium alloy can be properly modeled. The effects of extrusion temperatures and imposed boundary conditions on the resulting textures were investigated, and good agreement can be found between the simulated and the measured extrusion textures. The simulated results show that the DRX grains are responsible for the formation of the {2110} fiber component since the {1010} poles of the DRX grains are tilted away from those of the unrecrystallized grains during the formation of their high angle boundaries (HABs). Furthermore, the basal poles of the grains are favorably oriented to the transversal direction (TD) where the imposed deformation is larger due to lower slip resistance of the basal slip. The elevated temperature enhances the activity of pyramidal 〈c+a〉 slip modes and gives rise to a larger recrystallized volume fraction, resulting in a weakened extrusion texture.