Hybrid additive manufacturing of an electron beam powder bed fused Ti6Al4V by transient liquid phase bonding

Hybrid Additive Manufacturing (HAM) is a production strategy enhancing the flexibility of the already versatile Additive Manufacturing (AM) techniques. AM of Ti6Al4V, on the other hand, has been of great interest to numerous research works, thanks to the unique corrosion, biomedical and mechanical properties of the alloy. Hence, this research marks the first report on the HAM of Ti6Al4V by Transient Liquid Phase (TLP) bonding of an Electron Beam Powder Bed Fused (EB-PBF) sample to a conventional one. A copper interlayer was used for bonding, and the TLP process was performed at 890 °C and 970 °C for 60 min. Shear strength test was carried out and the results showed the highest shear strengths of 579.3 and 662.5 MPa for TLP bonding at 890 °C and 970 °C, respectively. By increasing the bonding temperature to 970 °C, no Cu-rich phases were observed in the microstructure, as opposed to the 890 °C samples, and a complete isothermal solidification without intermetallic phases was achieved. Moreover, the 970 °C TLP sample was featured with a much better microstructural integrity and homogeneity in both the base metals and the bonded zone. TLP bonding at 970 °C resulted in a more ductile fracture surface than that bonded at 890 °C. The strong differences between the two TLP bonds were primarily attributed to the faster diffusion rate of elements along the joint and base metal at higher temperatures.