Joint Mechanism of Ultrasonic Welding

Abstract

Much has not hitherto been known about the joint mechanism of ultrasonic welding. In the present work this mechanism has been studied by means of microscopic observation, X-ray diffraction, temperature measurement of joined parts, X-ray microanalysis, etc. The results obtained may be summarized as follows: (1) In the section of an ultrasonic bond, the temperature rise of the bond beyond the recrystallization temperature of material was revealed according to the microscopic observation. Neither intermetallic compounds nor other phases were observed in the interface by electron microscopy. (2) The recrystallization texture was observed by X-ray diffraction in the interface of the ultrasonic bond between two different foils, and neither intermetallic compounds nor other phases were observed in the X-ray diffraction pattern. (3) The variation in the half value breadth of X-ray diffraction lines obtained from the ultrasonic bond shows that the temperature rise in the interface of joined materials is by far larger than that in the place being in contact with the sonotrode tip. (4) The temperature of joined parts was measured with an alumel-chromel thermocouple and an oscillograph, and the temperature rise was found to be most affected by ultrasonic power. (5) X-ray microanalysis showed that the interatomic diffusion occurs in the ultrasonic bond between copper and titanium. (6) The joint strength between copper-beryllium alloys heat treated at 350•Ž for 15•`30min and silver-copper alloys was about twice as much as that obtained from unaged ones. The joint strength of the bond was markedly influenced by the aging condition for the age-hardenable alloy.