Weld joint characterization in ultrasonic welding of phosphor bronze sheets

Ultrasonic welding has been accomplishing as a popular joining method in the field of electrical and electronics components owing to its capability of making good quality similar and dissimilar joints in an extremely short duration consuming very less power. The present work investigates the effects of welding energy on the mechanical, thermal and microstructural characteristics of the weld joint. The ultrasonic welding is performed on 0.36 mm thick phosphor bronze (UNS C51100) sheets. It is observed that the values of peak interface temperature and tensile-shear strength increase with the welding energy. The failure mode changes from interfacial to nugget pull-out at considerably high energy level during the tensile-shear load test. There is a significant rise in the tensile-shear load initially but negligible change is observed in the last stage. The microstructural analysis using scanning electron microscope (SEM) has revealed that the joining line appears almost straight at low energy level but fades away at higher energy level. The bonding region ultimately acquires the shape of a wavy convoluted interface. Micro-bonding accompanied by interlocking is observed as the primary joining mechanism at high energy level.