Effect of weld tip geometry on ultrasonic welding of A6061 aluminum alloy

Authors ultrasonically welded A6061 aluminum alloy sheet using two types of weld tips with the different contact face geometry, and investigated the effect of the weld tip on the performance and interface structure of the welds. One type of tip has a cylindrical contact face without knurl, which is called C-tip in this study. The other type of tip has flat contact face with knurl, which is called K-tip in this study. The following main results were obtained.The strength of the joints welded using C-tip was higher than that welded using K-tip and the fluctuation in joint strength with C-tip was smaller. The C-tip could stably produce the higher strength joint. Using K-tip, the knurl indentations were made on the workpiece surface due to the pyramidal projections on the weld tip, and the indentation size expanded with welding time, resulted in the deterioration of the joint property. On the other hand, the indentation made on a workpiece surface by using C-tip showed a distinctive shape like an ellipse elongated perpendicular to the ultrasonic vibration, and the indentation grew with welding time.Using K-tip, unbonded regions remained at the weld interface due to the concave on the weld tip face. In the cross-sectional structure parallel to the workpiece width of the joint welded using C-type of tip, the distinctive feature was observed that the faying surface of the anvil workpiece was mixed with that of the sonotrode workpiece by intense plastic deformation and a horn-like protuberance intruding into the sonotrode workpiece was formed at the periphery of the welded area.