Spot welding between aluminum alloy and zn coated steel by friction stirring

Abstract

Application of aluminum alloy which is a typical lightweight material has been expected to achieve energy saving and prevention of pollution in many kinds of transportation vehicles. While the structure made of whole aluminum alloy, however, is lightweight, it still has problems, such as low mechanical strength and high cost. Hence, hybrid or joining structure made of aluminum alloy and steel seems to be reasonable because of its lightweight and higher strength. To make a hybrid structure for transportation vehicles, we examined welding by friction stirring between aluminum alloy and low carbon steel, which was welding without melted weld materials. As a result, welding between aluminum alloy and low carbon steel that had thin intermetallic compound at weld interface was obtained. In recent automobile manufacturing, zinc coated steel has been used as structural parts in general. On the welding between zinc coated steel and other materials such as aluminum alloy, existence of Zn layer between aluminum and steel have to be taken into account, to get high quality joint between the materials. In this study, the spot joining between aluminum alloy and several kind of zinc coated steels by friction stirring was carried out, and the effect of coated layer both on the weld strength and weld interface microstructure was investigated. As a results, joint between aluminum alloy and zinc coated steel was stronger than that between aluminum alloy and non coated steel, when coated layer was removed at weld interface by plastic flow of aluminum alloy.