Effects of external cooling on the formation of intermetallic compound in dissimilar resistance spot welding between steel and aluminum alloy

In dissimilar resistance spot welding between steel and aluminum alloy, it is known that when the intermetallic compound (IMC) is formed thickly, the joint strength decreases. Since IMC is formed by atomic diffusion caused by the temperature field at the joining interface, shortening the atomic diffusion time is effective in suppressing the growth of IMC. In this study, a temperature field control method focusing on the cooling process as one of the IMC suppression techniques was applied, and the effect of external cooling on the IMC formation state was investigated. As a result, it was clarified that spraying cooling gas using a gas spray device suppressed the IMC thickness and the Alrich IMC thickness, leading to an improvement in cross tension strength. Furthermore, the surface temperature of the Al alloy was confirmed to decrease under external cooling. Consequently, the increased temperature gradient between the Al alloy surface and the joining interface enhanced heat extraction at the interface, which is considered to have reduced the atomic diffusion time and thereby suppressed both the overall IMC thickness and the Alrich IMC thickness.