Welding characteristics and structures of same and different metal specimens using ultrasonic complex vibration welding equipments

Ultrasonic complex vibration welding of same and different metal specimens and structures of the welded area are studied using several complex vibration welding systems, scanning and transmission electron microscopes (SEM and TEM). Ultrasonic welding can weld various metal directly using vibration and static clamping pressure. The welding area is limited very narrow layer and can weld different metal specimens which have different melting temperature and difficult to weld by usual welding methods such as resistance welding. Ultrasonic complex vibration welding of two-dimensional vibration locus could be used for joining different metal specimens at multiple positions continuously and has superior quality compared with conventional ultrasonic welding with linear vibration locus. Welding of aluminum-copper, aluminum nickel plate specimens and aluminum alloy is essential for fuel cell, multi-layer battery or EDLC capacitor electrodes for electric or hybrid automobile and other various industry fields. For large electric current devices, multiple spot or seam welding is required. Ultrasonic complex vibration welding systems of 15 to 40 kHz were developed using (1) multiple transducers integrated with a transverse vibration disk, (2) complex vibration converter with diagonal slits. Elliptical to circular vibration loci are obtained at the welding tip and they are driven using several 500 W (1) and 2 kW (2) power amplifiers. Required vibration velocity and damage by vibration fatigue are small compared with conventional welding. Using the ultrasonic complex vibration welding systems, aluminum, copper, aluminum-copper and aluminum-nickel plate specimens were welded directly successfully at continuous multiple positions. Structures of these welded areas are observed using SEM and TEM. By observations of TEM images of cross sections of welded specimens, it was shown that these specimens were joined directly without any oxide, inter-metallic compound, mutual diffusion and any different structures. Required vibration velocity was one-third to quarter compared with conventional welding and weld strength near to material strength was obtained independent of specimen position and direction, and multiple or continuous welding is possible. Alumina coated aluminum alloy specimens were welded using complex vibration. The coated alumina layer was broken roughly in initial welding process and furthermore, broken into small alumina particles by ultrasonic complex vibration and finally dispersed throughout in welding specimens.