Effect of Bonding Temperature on the Joining of Ti-6Al-4V Alloy Using Cu Coatings and Sn Interlayers

Abstract

Titanium alloy Ti-6Al-4V samples were bonded together using Cu coatings and Sn interlayers. The bonding of titanium samples was successful at various temperatures (700-950 °C) which are below the β-transus temperature of Ti-6Al-4V alloy. An applied uniaxial pressure of 1 MPa and a short bonding time of 15 min were selected as bonding parameters. Scanning electron microscope and energy-dispersive spectroscopy showed that the dissolution of Ti in the joint region increases with the increase in bonding temperature. X-ray diffraction analysis of the fractured surfaces revealed that Sn5Ti6, Sn3Ti5 and SnTi3 intermetallic compounds (IMCs) were formed and dominated the joint structure. The shear strengths of the bonds increase with the increase in bonding temperature and reaches a maximum of 478 MPa for bond made at 950 °C. The microhardness analysis of the fractured surfaces compared to the base alloy confirmed the presence of the IMCs. X-ray photoelectron spectroscopy (XPS) analysis showed the presence of Ti at the top surface of the fractured bonds made at 700 °C which confirmed a successful joint evolution even at the lowest bonding temperature used. Atomic force microscopy observations for bonds made at 700 and 950 °C coincide with the XRD and XPS analysis and were able to reveal the remaining Cu particles on the substrates.