基于滑移/孪生耦合模型的镁合金多晶体塑性成形分析

镁合金的各向异性是由滑移和孪生共同作用产生,而孪生是协调镁合金塑性变形的重要机制。尤其在低温变形条件下,滑移和孪生相互协调并影响其成形性能。为准确描述镁合金成形过程的变形机制,文章建立了一种基于滑移和孪生相互耦合的多晶体塑性模型,并引入到有限元分析过程中。其中金属塑性流动,由每个晶粒内滑移面上沿滑移方向产生的剪切变形及孪生面上的孪生变形共同组成,进而采用率无关晶体塑性模型模拟了AZ31镁合金压缩过程,并给出了孪晶体积分数随时间的变化曲线。研究表明,孪晶体积分数随变形应力产生相应变化,并且基面滑移和孪生是影响镁合金室温成形性能及加工硬化的主要因素。

Effect of slip and twinning systems on the polycrystal plastic model for magnesium alloy

The plastic anisotropy of HCP metal is usually caused by preferred orientation of grains, which are developed by the combination role of the slip and twinning deformation at room temperature. Consideration of plastic anisotropy is essential in accurate simulations of metal forming processes. A new constitutive model for polycrystalline plastic deformation by slip and twinning combination has been formulated, and then introduced into a finite element program. Metal flow is assumed to occur by crystallographic slip on given slip and twinning systems within each crystal. Then compressed Mg alloy is studied using a rate independent polycrystalline plasticity finite element analysis. The ear distributions of polycrystalline are computed for different typical initial orientation cases. The values of the twinning factors associated with slip system deformation have deduced. It is been found that the twinning factors are various with the value of the stress. The basal slip and twinning system play the dominant role in the deformation of magnesium which may for the most part be attributed to the strain harden.