Easy disassembly of steel/aluminum joint by foaming of aluminum part with foaming agent sheet

The use of multi-materials, in which a wide variety of materials are used in the appropriate places, is being promoted to reduce carbon dioxide emissions. In the multi-materialization of automobiles, steel-aluminum joints are widely used. Friction stir welding (FSW) is used for joining steel and aluminum. Because of the solid state and short joining time of the FSW, the thickness of the brittle intermetallic compound layer can be minimized and high-strength joining can be achieved. Meanwhile, since recycling aluminum greatly reduces carbon dioxide emissions compared to the production of new ingots, easy disassembly technology is required. In this study, fabrication of thin foaming agent sheet was attempted. Then, we attempted to realize easy disassembly of steel/aluminum joints by FSW, which can realize strong joints, by using foaming agent sheets that can easily introduce foaming agent on joining interface during FSW. It was shown that foaming agent sheet can be prepared by solidifying foaming agent and pore morphology stabilizer powders using spark plasma sintering. It was also shown that even if a foaming agent sheet was introduced at the joining interface and FSW was performed, good jointing can be achieved. In addition, it was found that the introduction of a foaming agent sheet and foaming at the joining interface can significantly reduce the maximum disassembly load with fracturing at the joining interface. The above results indicate that the use of a foaming agent sheet can easily add an easy-disassembly characteristic to the area near the joining interface in the FSW process.