Influence of Diffusion Bonding Pressure on Microstructural Features and Strength Performance of Dissimilar Ti-6Al-4V Alloy and AISI 304 Steel Joints Developed Using Copper Interlayer

The joining of Ti-6Al-4V (Ti64) alloy and AISI 304 austenitic stainless steel (ASS 304) carries significant importance in aeroengines for turbine blade applications. However, it is difficult to join using fusion welding. The fusion welding of Ti64 alloy and ASS 304 steel promotes the evolution of various Fe-Cr-Ti and Fe-Ti intermetallics in weld zone owing to limited solid solubility of Fe, Cr, Ti, and Ni with each other. The evolution of these intermetallics deteriorates the strength performance of joints. Hence for joining Ti64 alloy and ASS 304 steel, vacuum diffusion bonding (VDB) method is employed with thin copper (Cu) foil as an interlayer. The DB pressure extends significant influence on microstructural evolution and strength of joints. So, for the feasibility of joining Ti64 alloy and ASS 304 steel, the effect of DB pressure on microstructure and strength of joints is investigated. Results showed that the dissimilar joints of Ti64 alloy and ASS 304 steel developed using the DB pressure of 14 MPa exhibited greater lap shear strength (LSS) and bonding strength (BS) of 180 MPa and 268 MPa, respectively. It is attributed to the improved coalescence of joining interface and the development of ideal bonding width with the least amount of embrittlement consequences. An increase in DB pressure increases the width of the diffusion region which promotes the development of detrimental intermetallics of Ti-Fe and deteriorates the strength of dissimilar joints.