Transient Liquid Phase Bonding of AA-6063 to UNS S32304 Using Cu Interlayer

Transient liquid phase bonding of AA-6063 and UNS S32304 was performed in an inert atmosphere using a Gleeble (model 3800) thermo-mechanical simulator. Base metals were machined to rectangular dimensions of 30 mm x 15 mm. Aluminum samples were fabricated from a U-shaped extruded Al-6063 profile with 2 mm thick, while duplex stainless steel samples were in form of coupons with 1 mm thick. A copper foil with 99.9% purity and 10 μm thickness was used as an interlayer between the base metal sheets. A compression load of 0.2KN was applied horizontally to the specimens. The effect of bonding temperature (550 °C, 555 °C, 560 °C and 570 °C) was studied on the microstructure of the joints using light and scanning electron microscopy. Compositional changes across the joint region were studied using energy dispersive X-ray spectroscopy. Although copper diffusion into aluminum results in an Al-Cu eutectic structure, the oxide layer on the aluminum surface controls the dissolution behavior of Cu and extent of wettability with the base metals. Although a defect free joint was produced at 570 °C, X-ray diffraction results detected the formation of intermetallic compounds (FeAl3).