Improvement of ultrasonic weld strength of Al-Mg alloys by alcohol adhesion-ultrasonic welding of Al-Mg alloys

摘要

The present research study is intended to improve the ultrasonic weldability of Al-Mg alloys, its specific purpose being to examine the effects on ultrasonic weldability of specimen preheating and alcohol adhesion on the faying surface. The results obtained may be summarised as follows. The weld strength is improved by specimen preheating. In the as-electrolytically polished case, the change in the weld strength associated with an increase in clamping load is maximised at some specific clamping load. When ethanol is applied to the faying surface, how ever, a high weld strength is obtained in the high clamping load range that shows a falling trend in the as-electrolytically polished case. The specimen temperature obtained during welding with ethanol adhesion is higher than in the as-electrolytically polished case. The weld strength at a welding time of 1.0 s increases with a rising specimen temperature. During ethanol adhesion, amplified relative motion between the specimens is obtained in the initial stage of welding. When water is arranged to adhere to the faying surface or when carbon is vapour-deposited on the faying surface, the weld strength is equivalent to that obtained in the as-electrolytically polished case, but no ethanol-equivalent effect is obtained. During ethanol adhesion, the contact area sharply increases up to a welding time of 0.75 s. Scratch marks (part S) indicating surface segregation of Mg are broken down by activation of relative motion between the specimens and by specimen softening due to the temperature rise during welding. By this means, the dimpled area (part D) increases, and the ultrasonic weldability of Al-Mg alloys improves.