Microstructural and mechanical characterization of diffusion bonded hybrid joints

Abstract

Ti-alloys, particularly TiAl, are becoming attractive for the use in the production of high-temperature components such as turbine blades and exhaust valves, owing to their low density. However, these components may not be cost-effectively cast totally from TiAl alloys and casting defects may occur in investment casting of these complex parts. Other manufacturing technologies, such as machining, cannot be economically employed in these very hard and brittle materials. Production of bi-material or even multi-material TiAl components can therefore offer an alternative fabrication route provided that the joining and joint properties of these materials are well understood. In this study, the diffusion bondability and joint characteristics of TiAl and Ti–6Al–4V alloys were studied. These two different materials were joined by using various bonding parameters. Metallographic investigations were conducted for characterization of the interface region of these dissimilar joints. Furthermore, the mechanical behavior of the bond interface was evaluated by shear testing. Both results on the microstructural and mechanical characterization provided the optimum bonding conditions for the production of TiAl–Ti6Al4V hybrid joints.