Vaporizing Foil Actuator Welding of AA6061 With Cu110: Effect of Heat Treatment Cycles on Mechanical Properties and Microstructure

This work aims to study the effect of microstructure of the weld between aluminum alloy AA6061 and commercially pure copper, Cu 110, on its mechanical properties. AA6061-T6 and T4 aluminum sheets of 1 mm thickness were launched towards copper targets using the Vaporizing Foil Actuator (VFA) tool operating at 8 kJ input energy level. Flyer plate velocities, measured via photonic Doppler velocimetry (PDV), were observed to be approximately 800 m/s. All the welded samples were subjected to instrumented peel testing, microhardness testing, energy-dispersive x-ray spectroscopy (EDS), and SEM. The welded joints had cracks which ran through the continuous intermetallic layers and stopped upon encountering a ductile metallic wave. The welds created with T6 temper flyer sheets were found to have smaller regions with wavy interfaces free of intermetallics as compared to those created with T4 temper flyer sheets. Peel strength tests of the two types of welds resulted in failure along the interface in case of the T6 flyer welds, while the failure generally occurred in the parent aluminum in the case of the T4 flyer welds. Half of the T4 flyer welds were subjected to aging for 18 hours at 160 °C to convert the aluminum sheet back to T6 condition. Although the flyer material did not attain the hardness of the original T6 material, it was found to be significantly stronger than the T4 material. These welds retained their strengths after the aging process and diffusion across the interface was insignificant.