Characterisation of aluminium alloy 6061 for the ultrasonic consolidation process

Ultrasonic consolidation (UC) is a freeform fabrication technique developed for the layered fabrication of metal parts. The process uses a high intensity ultrasonic energy source to induce combined static and oscillating shear forces within layers of metal foil to produce solid-state bonds. This paper will consider control parameter optimisation and surface preparation issues, for the production of aluminium alloy 6061 specimens. It will assess weld quality through both mechanical testing and optical observation. Aluminium 6061 specimens were successfully welded by the UC machine using both unprepared and surface prepared foils. In the unprepared specimens, thick oxide films exist along the whole specimen length of the weld interface. Results showed that the dynamic interfacial stresses, generated under UC conditions, compact the oxide layer to form brittle, ceramic bonds at the weld interface. A simple cleaning procedure increased metallurgical bonds, within the weld interface, by up to 45%. A general process window was produced for 6061 alloy based on a combination of the peel test data and microstructural analysis. (C) 2003 Elsevier B.V. All rights reserved.