Accessing collision welding process window for titanium/copper welds with vaporizing foil actuators and grooved targets

Abstract

A method for accurate, low-cost, lab-scale determination of the optimal collision angles and velocities for collision welding of a given combination of materials has been introduced. 0.508mm thick grade 2 CP Ti sheets were launched at various velocities toward a Cu 110 target with grooves of angles ranging from 8° to 28°, machined on the collision side. Capacitor bank-driven aluminum vaporizing foil actuators operated at input energy levels up to 12kJ and currents up to 140kA were used to launch the flyer sheets. Velocity was measured with high temporal resolution using a photonic Doppler velocimetry (PDV) system. Collision velocities ranged from 440m/s to 860m/s. The welded assemblies were sectioned and the weld interfaces were observed via scanning electron microscopy. For each collision angle there were certain collision velocities which yielded a wavy interface. Welding velocity for transition from smooth to wavy interfaces for each collision angle was used to determine the corresponding transition Reynolds number and was compared to existing results in literature. The uniqueness of this process lies in its small scale and ease of implementation.