Effect of surface roughness on bonding interface formation of steel and Ni by ultrasonic welding

ABSTRACT

Ultrasonic welding is a solid-state bonding technique available in bonding steels and other metals. To understand the effect of roughness on the evolution of bonding strength, Ni and steel were employed. It is found that when smooth bonding surfaces by mirror polishing, a rapid evolution of bonding strength can be obtained owing to the extensive formation of contact areas. When the bonding surfaces become rougher, the evolution of bonding strength is retarded at an early stage; this can be attributed to the presence of rough peaks that result in a lower fraction of contact area and concentrated clamping stress. As sufficient contact areas are produced at a longer welding time, a rapid increase in bonding strength is correspondingly obtained.

KEYWORDS:

• Ultrasonic welding
• surface roughness
• steel

Acknowledgements

The authors would like to thank Professor Manabu Enoki for his allowance to use three-dimensional (3D) laser microscope (OLS-4000, Olympus).

Disclosure statement

No potential conflict of interest was reported by the authors.