Impact Welding of Aluminum Alloy 6061 to Dual Phase 780 Steel Using Vaporizing Foil Actuator

Vaporizing Foil Actuators (VFA) are based on the phenomenon of rapid vaporization of thin metallic foils and wires, caused by passage of a capacitor bank driven current on the order of 100 kA. The burst of the conductor is accompanied with a high-pressure pulse, which can be used for working metal at high strain rates. This paper focuses on the use of VFA for collision welding of dissimilar metals, in particular, aluminum and steel. Aluminum alloy 6061 sheets of 1 mm thickness were launched to velocities in excess of 650 m/s with input electrical energy of 8 kJ into 0.0762 mm thick, dog-bone shaped aluminum foil actuators. Target sheets made from dual phase steel (DP780) were impacted with the aluminum flyer sheet, and solid state impact welds were created. During mechanical testing, many samples failed outside the weld area, thereby indicating that the weld was stronger than the parent aluminum. The samples that failed inside the weld region were found to have regions of brittle as well as ductile fracture. Metallography of the samples revealed that the interfaces had a wavy morphology that is typical for impact welds. Intermittent regions of intermetallic compounds were seen along the interface.