铝铜搅拌摩擦焊搭接接头的组织性能及金属迁移行为研究

发布时间：2018-07-28 18:30

【摘要】：1060铝合金和T2紫铜以其良好的物理力学性能而被广泛应用于工业领域,铝-铜异种金属的连接也是国内外研究的热点之一。搅拌摩擦焊作为一种金属固相连接方法,常用于连接铝、镁、铜等有色金属。铝铜异种金属搅拌摩擦搭接焊工艺目前尚处于实验研究阶段,对铝铜异种金属搭接接头中金属迁移行为的研究报道还不多。研究并创新铝铜搅拌摩擦焊搭接工艺,对于1060铝合金和T2紫铜应用的推广具有基础意义,研究接头金属流动行为对提高接头性能具有指导意义。本文采用搅拌摩擦焊工艺对厚度6mm的1060铝合金板材和2mm的T2紫铜板材进行搭接试验,其中采用铜铝板材进行第一次搭接形成Ⅰ次焊缝,在铝-铜双层接头基础上进行第二次焊接,形成铜-铝-铜三层接头,第二次搭接的焊缝称为Ⅱ次焊缝。通过改变焊接工艺参数、搭接材料组合以及搅拌针的长度,研究铝铜搭接接头的组织形貌、力学性能和金属流动行为。研究发现:搅拌头旋转速率n=800rpm,焊接速度v=90mm/min参数下得到表面成形良好的焊缝;n=1100rpm,v=80mm/min时,焊缝剪切强度达到铝母材抗剪强度的96.5%,铜母材的43.4%。焊缝中发生共晶反应生成金属间化合物CuAl2和Cu9Al4。在铜-铝-铜三层接头中,二次焊接扩大了接头中高硬度组织的区域,提高了硬度峰值。Ⅱ次焊缝宏观缺陷比Ⅰ次焊缝多,抗剪强度普遍低于Ⅰ次焊缝。材料厚度一定时,搅拌针越长,焊缝成形性和接头强度越差。对搭接接头试样的横截面、纵截面、轴肩摩擦平面和铝铜界面平面进行金属流动行为分析发现,在焊缝厚度方向塑性金属迁移分为三个区域:轴肩扰动区金属做水平圆周运动,紊流区金属发生垂直方向的对流运动,搅拌区金属发生椭圆形环流。在轴肩摩擦平面,塑性金属一方面在前进侧沿径向迁移,一方面受轴肩推动向焊接方向迁移。在铝铜界面平面,大量的铝铜相互迁移形成混合组织,混合组织发生短距离的径向迁移。二次焊接使焊缝截面紊流区混合组织减少,使铝铜界面平面金属径向迁移距离变小,迁移至母材中的颗粒状铜增多。在焊缝截面,搅拌针越长上层金属向下迁移距离越小。在焊缝轴肩摩擦平面,搅拌针越长,金属沿径向迁移的距离越大,在铝铜界面平面,搅拌针越长,金属流动性越差,沿径向迁移的距离更小且更不均匀。
[Abstract]:1060 aluminum alloy and T2 copper are widely used in the industrial field because of their good physical and mechanical properties. The connection of aluminum and copper dissimilar metals is also one of the hot research topics at home and abroad. Friction stir welding (FSW), as a solid metal bonding method, is often used to connect non-ferrous metals such as aluminum, magnesium and copper. The friction stir welding process of aluminum and copper dissimilar metals is still in the experimental stage, and there are few reports on the metal transfer behavior in the aluminum copper dissimilar metal lap joints. The study and innovation of aluminum copper friction stir welding lap welding technology is of fundamental significance for the application of 1060 aluminum alloy and T2 copper, and the study of metal flow behavior of joints is of guiding significance to improve the joint properties. In this paper, friction stir welding (FSW) is used to test 1060 aluminum alloy plate with thickness 6mm and T2 copper plate with 2mm thickness. The second welding is carried out on the basis of Al-Cu double layer joint to form the Cu-Al-Cu three-layer joint. The second lap weld is called the second weld. The microstructure, mechanical properties and metal flow behavior of Al-Cu lap joints were studied by changing the welding process parameters, lap material combinations and the length of agitated needles. The results show that the shear strength of the weld can reach 96.5mm of the aluminum base metal and 43.4 of the copper base metal under the rotating rate of the stirring head n = 800rpm, and the welding speed of v=90mm/min. The weld seam with good surface forming is obtained when the weld surface is formed at 80mm / min. The shear strength of the weld is 96.5mm / min of the aluminum base metal, and that of the copper base metal is 43.4mm / min. The intermetallic compounds CuAl2 and Cu9Al4were formed by eutectic reaction in the weld. In the copper-aluminum-copper three-layer joint, the area of high hardness microstructure in the joint was enlarged by secondary welding, and the peak hardness was increased. The macroscopic defect of the second weld was more than that of the first weld, and the shear strength was generally lower than that of the first weld. When the material thickness is constant, the longer the stirring needle is, the worse the weld formability and joint strength are. The metal flow behavior in the cross section, longitudinal section, shoulder friction plane and aluminum copper interface plane of the lap joint specimen is analyzed. It is found that the plastic metal migration in the weld thickness direction is divided into three regions: the horizontal circular movement of the metal in the axial shoulder disturbance zone. In turbulent region, the convection movement of metal in vertical direction and the elliptical circulation of metal in agitated zone occur. In the axial shoulder friction plane, the plastic metal moves along the radial direction at the forward side on the one hand, and to the welding direction on the other hand by the shaft shoulder. In the interface plane of aluminum and copper, a large number of aluminum and copper migrated to form mixed structure, and the mixed structure moved in a short distance. Secondary welding reduces the mixed microstructure in turbulent zone of weld section, reduces the radial migration distance of planar metal at the interface between aluminum and copper, and increases the amount of granular copper migrating to the base metal. In the weld section, the longer the stirring needle is, the smaller the downward migration distance of the upper metal is. In the friction plane of weld shaft shoulder, the longer the stirring needle, the longer the distance of metal moving along the radial direction. In the plane of Al-Cu interface, the longer the stirring needle is, the worse the metal fluidity is, and the smaller and more uneven the distance along the radial migration is.
【学位授予单位】：江苏科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG453.9

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