Abstract
Ultrasonic bonding process of A6061 alloys is investigated focusing on the growth of micro-bonds initially formed on the bonding interface. The interfacial condition is controlled by partially anodic oxidizing to the surface. The growth of the micro-bonds locally formed in the initial stage of joining in the absence of an anodic oxide film is considered from the viewpoint of the relative motions of the bonding materials and the shear deformation caused by the relative motions. Dispersed initial bonds formed on the non-anodized surfaces hinder the relative motion between the bonding materials. By applying partial anodic oxidizing, the formation of the initial bonds is concentrated in the non-anodized areas. The localized bonds expand with shear deformation and develop into plastic flow, leading to the increase of joint strength. The shear force applied by the ultrasonic horn tip and anvil contributes to the plastic deformation in the later stages of joining. It is revealed that the formation of the localized initial bonds by means of the partial anodic oxidizing promotes the relative motion of the bonding materials and the resultant growth of the initial bonds. Localization of the initial bonds can be an effective means of increasing joint strength and reducing joint strength variation.
