Influence of Al and Ni interlayers on interfacial strength evolution during ultrasonic welding of ultra-low-carbon steel and pure Ti

Abstract

This study investigated the effect of interlayer metals, particularly Al and Ni, on strength evolution during the ultrasonic welding (USW) of steel and Ti. It was found that the Al interlayer had an exceptional effect on accelerating strength evolution from 0 up to 1000 N in 0.1 s and up to 2000 N (26.7 MPa of lap shear strength) in 0.25 s. This causes base metal fracture with a higher bonding strength than the case without interlayer (700 N in 0.25 s). It was also found that when using Ni interlayer, the bonding strength was gradually increased to approximately 1000 N until 1.5 s of welding, slower than using Al interlayer. Microstructural analyses revealed that the Al interlayer was subjected to severe deformation and adhesion on base metals, leading to extensive contact to achieve bonding. In contrast, the less-deformable Ni interlayer exhibited a slow effect on strength evolution owing to less contact and the fracture within Ti during USW.