Effect of process parameters on bond formation during ultrasonic consolidation of aluminum alloy 3003

Ultrasonic consolidation (UC) is a novel additive manufacturing process wherein three-dimensional metallic objects are fabricated layer by layer in an automated fashion from thin metal foils. The process has immense potential for fabrication of injection molding tooling with conformal cooling channels, fiber-reinforced composites, multi-material structures, smart structures, and others. The proportion of bonded area in relation to the total interface length, termed linear weld density (LWD), is perhaps the most important quality attribute of UC parts. A high level of LWD is desirable in parts intended for load-bearing structural applications. It is therefore necessary to understand what factors influence LWD and devise methods to enhance bond formation during ultrasonic consolidation. The current work elucidates the effects of process parameters on LWD in Al alloy 3003 UC parts. A set of optimum parameters for Al 3003 part fabrication using UC has been obtained, which may vary, however, for different foil materials and sonotrode/foil frictional conditions. The beneficial effects of using elevated substrate temperatures and its implications on overall manufacturing flexibility and the trade-offs between part quality and build time are discussed. The mechanism of ultrasonic welding is discussed based on oxide layer removal and plastic deformation at the weld interface. A preliminary understanding of defect formation during UC is presented, based on which a method (involving surface machining) for obtaining near-100% LWD is demonstrated. The findings of the current work encourage wider utilization of the UC process and could stimulate further research in the areas of UC process development and modeling.