工具尺寸对铝-钢异种金属搅拌摩擦搭焊接头组织与性能的影响

Influence of Tool Size on the Microstructure and Mechanical Properties of Friction Stir Lap Welded Dissimilar Aluminum-steel Joint

铝合金与钢的异种连接是汽车轻量化制造的关键,然而采用传统的熔化焊工艺很难得到高质量焊缝。本文选用不同尺寸的焊接工具对1.2mm厚的5182铝合金和DP1180高强钢进行搅拌摩擦搭焊。微观组织分析表明,在转速为800r/min,焊接速度为50mm/min的参数条件下,采用两种尺寸的工具均可得到无缺陷的接头,且小尺寸工具条件下接头生成明显的"Hook"缺陷,采用大尺寸工具时"Hook"缺陷显著弱化,此时铝和钢的反应充分,堆垛层状结构更为明显。由于堆垛层状结构中金属间化合物的存在,界面附近硬度波动较大,最高硬度可达641HV,明显高于钢母材。采用小尺寸工具时,由于搭接面积较小,接头拉伸剪切性能较差,全部沿界面开裂;而采用大尺寸工具时,当铝合金位于前进侧的条件下接头性能优异,断裂于铝合金侧,最大剪切力高达3.42k N,表明对铝-钢异种金属进行搅拌摩擦搭接可获得高质量的焊接效果。

Dissimilar joining of Al alloy and steel is a key issue in the lightweight manufacture of the automotive industry, however achieving good weld is very difficult for the traditional fusion welding methods. In this study, 5182 Al alloy and DP1180 high strength steel plates with 1.2 mm in thickness are friction stir lap welded using different tool sizes. Microstructure analysis indicates that defect-free joints are obtained with both tool sizes under a rotation rate of 800 r/min and a welding speed of 50 mm/min. Obvious "Hook" defect forms in the joint with small tool, however it is significantly inhibited while using the big tool, and the stacking layered structure is more obvious due to the sufficient reaction between Al and steel in this case. Hardness values sharply fluctuates near the interface, due to the formation of the intermetallic compounds in the stacking layered structure, and the highest hardness value is 641 HV which is higher than that of the steel base metal. When using the small tool, weak tensile shear properties are obtained with the joints failed along the interface due to the small lap area;however, sound tensile shear properties are obtained with the joints failed at the Al side using the big tool when the Al alloy plate is located at the advancing side, and the shear force is as high as 3.42 k N. This indicates that high quality Al-steel dissimilar lap joint can be successfully obtained by friction stir lap welding.