Production and Bond Strength of Similar-Titanium Ultrasonic Welded Joints

Abstract

The joinability of unalloyed titanium and the bond strength of similar-titanium welded joints by ultrasonic welding were investigated. It turned out that sound welded joints of similar-titanium were obtained by using the jig for fixing both base metals. In the case of non-fixing and fixing the lower base metal, sound welded joints weren't usually obtained due to the slip between the two base metals. Producing welded joints having sufficient bond strength required a certain threshold value of the ultrasonic energy. When the ultrasonic welding was carried out under the condition where the ultrasonic energy was higher than a threshold value (approximately 2000 W•s), the welded joints were fractured within the titanium base metal but not at the interface. The values of the bond strength were associated with the fixing method and the surface roughness of the base metals. The bond interface was joined metallurgically for the most part, although some small voids were observed on the bond interface by SEM and EPMA observation.