Effects of Thickness Combinations on Joint Properties and Process Windows in Ultrasonic Metal Welding

A single transducer wedge-reed ultrasonic welder has been used to make welds, in the non-age hardening aluminum alloy AA5754. A range of thickness combinations, varying from 1.2 mm to 2.5 mm, have been ultrasonically welded. A matrix of process parameters (input energy, impedance matching setting, tip clamp pressure and power) have been used to achieve high strength joints. Samples were welded in standard configuration for a tensile lap-shear test, which has been used to determine failure strength and type of failure. Optical microscopy has been used to reveal the bonding mechanisms. Variations in strength and failure mode have been related to changing process parameters and material thickness. It has been observed that stacking sequence has little effect on overall strength. Optimization of process parameters rather than the stack-up sequence has been shown to give the largest gains in joint strength.