Vaporizing foil welding: A new tool for collision welding

A new method for implementing collision welding at a laboratory scale has been developed. The pressure that drives the flyer plate toward the target is created by electrically driven rapid vaporization of a thin metallic conductor, rather than by chemical explosives or magnetic forces. Dissimilar welding couples of copper-titanium, copper-steel, aluminum-copper, aluminummagnesium and titanium-steel have been successfully created with the same set of input parameters (foil driver geometry, input energy and standoff distance). Instrumented peel tests, lap shear tests, and optical and scanning electron microscopy reveal a broad spectrum of strengths and interface microstructures. For example, copper-titanium and copper-steel welds are strong and display wavy interfaces characteristic of collision welds, with little intermetallics or void formation. The other combinations have brittle interfaces with intermetallics and defects with the collision welding parameters used presently. The ideal impact angle for copper-titanium, with the currently used input energy, was identified to be 20°. Peak velocities of up to 560 m/s were observed for titanium flyer sheets. This work introduces the new technique; further research will be done on geometrical, material, and electrical parameters of the process.