The objective of this study is to clarify the effects of materials hardness, thermal conductivity and faying surface roughness on the bonding strength of the dissimilar-metal joint performed with ultrasonic welding process. The employed combinations between the dissimilar metals were of aluminum-copper and aluminum-austenitic stainless steel (SUS304). The following results were obtained in this study.
The strength of the joint between aluminum and copper with high thermal conductivity was decreased with increasing the surface roughness of the metal having higher hardness, the copper in this case, and with increasing the thickness of the surface oxide film of the metals.
When SUS304 with low thermal conductivity is welded to aluminum, a reliable joint can be achieved despite the condition of the faying surface. This is attributed that the oxide film on the aluminum surface is easy to be broken because the considerable increase in the temperature at the welding interface due to the low thermal conductivity of SUS304 makes the aluminum more plastically deformable.
