The ultrasonic welding method has been expected to replace other welding and brazing processes, and this paper is concerned with an experimental study on the ultrasonic welding of an aluminum alloy onto other three aluminum alloys. In this study the relation between energy density and welding pressure in welding certain types of aluminum alloys was clarified. For example, the ultrasonic welding of an aluminum alloy can be accomplished under the condition E = K1Pn1 < f(P,E) < E = K2Pn2 (E: energy density, P: welding pressure, K, n: coefficients). The welding energy increases with an increasing in welding pressure, and decreases with a decrease in the size of the material on the anvil side. The welding energy is effectively used in the ultrasonic welding of a flexible, narrow material with a narrow pressurization area. Weldability can be evaluated by observing the amount of subduction of the welding material. Furthermore, the oxide film and organic coating are periodically removed from bonded interfaces by ultrasonic wave vibration.
