Ultrasonic joining of aluminum/titanium joints for hybrid lightweight applications

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Hybrid lightweight design dominates the development of future vehicle concepts in traffic engineering and the aerospace industry. To realize such multi-material systems appropriate and effective joining technologies are necessary. In this project ultrasonic metal welding will be investigated to realize aluminum-titanium hybrid joints in the solid state. Important structural aluminum and titanium alloys were chosen to produce high strength joints by using advanced process control and new welding tools. To identify the best process variant for structural applications a direct comparison of ultrasonic spot and torsion welding technique will be studied. Detailed experiments to the kinematics during ultrasonic welding are central points of interest, which are examined by laser vibrometry online. The process parameters welding force, oscillation amplitude and welding energy are determined by using modern statistical methods for the design of experiments. The bonding phenomena are related to the process variant and its specific process parameters and should be described in detail. Possible interfacial reactions like diffusion, formation of mixed crystals, and removal of passivation layers should be confirmed by electron microscopy and high-resolution spectroscopy. Finally a bonding model for ultrasonic welding of Al / Ti hybrids should be developed.