Diffusion bonding of Al7075 to Ti-6Al-4V using Sn-10Zn-3.5Bi as interlayer

Joining of two dissimilar aerospace alloys Al7075 and Ti-6Al-4V was carried out using TLP diffusion bonding process and 50 μm thick Sn-10Zn-3.5Bi foil as interlayer. Before bonding process, Cu coatings were electrodeposited onto the Ti-6Al-4V and Al7075 surfaces. Bonds were made at 500 ˚C and for various bonding times. Light Microscopy (LM), Scanning Electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) were used to investigate the microstructural development across the joints. The concentration of Sn reduces at the joint center with increasing bonding time. At low bonding times, Al2Cu eutectic was formed along the Al7075 grain boundaries. Also, TiAl and Ti3Al intermetallics were formed at bonding time of 45 min. Mechanical properties of the joint were examined by measuring microhardness and shear strength. The results showed that as bonding time increases up to 45 minutes, intermetallic compounds formation increases hardness. The strength of the bonds increases with increasing bonding time and reaches to 29 MPa at 45 minutes and no noticeable changes were seen in strength by further bonding time increasing.