FAST-DB: A novel processing route to produce dissimilar titanium alloy aerospace components from waste powder.

Titanium alloys are used extensively within the aerospace sector due to their good combination of high strength-to-weight ratio and corrosion resistance. Many of the aerospace components are exposed to extreme service stresses and temperatures, which in some applications could compromise the components performance if a single titanium alloy is used. A potential design solution is to use dissimilar titanium alloys in subcomponent regions, achieved through diffusion bonding of powders via field assisted sintering technology (termed FAST-DB) and subsequent hot forging (FAST-forge). For this manufacturing route to be successful, it is key to demonstrate that the diffusion bond does not compromise the integrity of the component. Furthermore, it is important to understand how a dissimilar diffusion bond will impact the machining operation in the final stages of the manufacturing route.

In this research program, titanium alloy demonstrators are produced from oversized, AM titanium powders in just two solid state processing steps: FAST-DB and hot forging. The integrity of the FAST-DB components is evaluated by combining tensile testing tests and digital image correlation (DIC). The results showed a dissimilar rate of deformation between both titanium and the failure of these samples always occurred in the lowest strength alloy and far removed from the bond.

The machining of multi-material components is a key part of the manufacturing route. Therefore, the microstructural damage and the forces generated in multiple titanium alloy diffusion bonds during machining trials have been assessed. The results showed different results depending on the machining direction, with a preferential direction detected when machining dissimilar titanium alloys.

The positive results in this work provide increased confidence in the use of FAST to produce near-net shaped aerospace components from dissimilar titanium alloy powders.