Solid state joining of aluminum, titanium and their hybrids by ultrasonic torsion welding

Solid state joining by the ultrasonic torsion welding technology has been investigated for light metal hybrid joints of aluminum AA1199 (Al4N) and cp-titanium grade 1. Before the welding experiments the materials were thoroughly characterized in the initial state and a surface pre-treatment was developed to increase reproducibility and comparability between individual experiments. On the system side a clamping device designed for the specimen geometry of the single overlap joint and a special welding tool for joints with titanium as upper joining partner were developed. Statistical test methods were used to determine optimized process parameters for ultrasonic torsion welding of the light metals. During the welding process the relevant properties like temperatures and ultrasonic oscillations were measured. Afterwards the joints were tested under tensile shear loading. Detailed light, scanning electron and transmission electron microscopy of the joining zone as well as fracture surface analysis were carried out to describe the bonding mechanisms.