FAST-DB: A New Approach of Joining Dissimilar Titanium Alloys in the Solid State

Field assisted sintering technology (FAST) or spark plasma sintering (SPS) is becoming an effective low energy hybrid process to consolidate metallic powders without the need for a canning stage. Such technology combined with subsequent cold and hot forging steps could enable titanium powder to be manufactured into components in 2 or 3 steps, providing a step change in the economics of titanium alloys. FAST-Diffusion Bond (or FAST-DB) is a new solid state approach to joining dissimilar titanium alloys.

Often, the stresses applied to components in service can vary from one specific region to another. For example, a compressor blade requires good fatigue properties at the root and creep resistance in the aerofoil section. To improve the performance of these components, dissimilar titanium alloys can be used in different regions to optimise the mechanical properties. To demonstrate this technology, FAST-DB rod preforms have been closed die forged to produce connecting rods. By doing so, the bonds are subjected to various strains, and bond property evolution occurs.

Multiple dissimilar titanium diffusion bonds that are incorporated into the connecting rods have been analysed, including microstructures, elemental diffusion, hardness profiles, and tensile strength. Commercial software has also been used to predict the diffusion behaviour of the dissimilar bonds.