Transient liquid phase (TLP) bonding of Al7075 to Ti–6Al–4V alloy

TLP diffusion bonding of two dissimilar aerospace alloys, Ti–6Al–4V and Al7075, was carried out at 500 °C using 22 μm thick Cu interlayers for various bonding times. Joint formation was attributed to the solid-state diffusion of Cu into the Ti alloy and Al7075 alloy followed by eutectic formation and isothermal solidification along the Cu/Al7075 interface. Examination of the joint region using SEM, EDS and XPS showed the formation of eutectic phases such as, Ө(Al2Cu), T(Al2Mg3Zn3) and Al13Fe along grain boundaries within the Al7075 matrix. At the Cu/Ti alloy bond interface a solid-state bond formed resulting in a Cu3Ti2 phase formation along this interface. The joint region homogenized with increasing bonding time and gave the highest bond strength of 19.5 MPa after a bonding time of 30 min.