型腔结构对AZ31镁合金连续挤压扩展成形规律的影响

Expansion Forming of AZ31 Magnesium Alloy with Two Types of Cavity Structures during Continuous Extrusion Process

应用连续挤压扩展成形方式制造镁合金板材,型腔结构对镁合金这种变形条件敏感的材料影响明显。采用DEFORM-3D软件,针对两种型腔结构,数值模拟了厚度为8 mm,宽度尺寸分别为80,120和160 mm 3种规格的镁板材的连续挤压扩展成形过程,探讨了型腔结构和产品尺寸变化与流动速度的关系。结果表明,增加型腔深度,低速区尺寸增大,高速区流动速度降低,模口处流动速度差减小。随着产品宽度增大,流动速度降低,模口处流速均方差增大,流动的不均匀程度增加。型腔结构和产品尺寸变化对坯料流动速度的影响缘于模壁摩擦力的作用。流动通道短,心部区域受到的摩擦阻力作用小,加大了心部和模壁区域的流动速度差。反之,增加型腔深度,模壁面积增加,摩擦力的作用区域增加,起到均匀流动速度的作用。

Continuous extrusion expansion forming process was implemented to produce magnesium alloy sheets. Cavity structure had significant influence on expansion forming of magnesium alloy which was sensitive to deformation conditions. The expansion forming processes with two types of cavity structures were simulated with DEFORM-3D software. Three kinds of magnesium sheets were studied,which were 8 mm in thickness and 80,120 and 160 mm in width,respectively. The relationships between flow velocity and variations of cavity structure and product dimension were discussed. The results showed that when the cavity depth increased,the dimension of low velocity region increased,the flow velocity of high velocity region reduced,and the flow velocity difference at the die exit decreased. When the product widths increased,the flow velocity reduced,and the standard deviation of velocity at the die exit and the non-uniformity of flow increased. The effect of cavity structure and product dimension change on flow velocity resulted from the friction action of cavity walls. When the flow channel was short,the effect of friction resistance on core region was small,which increased the flow velocity difference between core region and cavity wall region. Conversely,when increasing the depth of cavity,the region of friction action increased because the area of cavity wall enlarged,the friction played the role of homogenizing flow velocity.