Development of a Powder Based Manufacturing Route for Affordable Titanium Aluminide Sheet for Nacelle Engine Applications

Intermetallic titanium aluminides (TiAl) based alloys provide a good combination of low density, high strength at elevated temperatures, good oxidation and hot gas corrosion resistance, providing excellent engineering properties for structural aerospace applications and automotive turbocharger applications. They have been proven in recent applications, such as the low-pressure turbine (LPT) blades in the GEnx commercial aircraft engine (Boeing 787). TiAl based alloys provide unique properties for aerostructural high temperature applications and can replace heavier nickel-based superalloys.

Many potential future applications will require TiAl based alloys in sheet form which requires homogeneous ingot feedstock, extrusion/forging and controlled hot and cold rolling schedules. Multi-pass schedules for TiAl based alloys from ingot is challenging, as process windows are very narrow due to micro-segregation during the casting process. And therefore, further research is needed to increase the use of TiAl based alloys from powder metallurgy routes in wider structural aerospace applications, such as engine nacelle parts, which are reaching their operating limits. Outputs generated from this EngD/PHD will provide further confidence in the processing of such alloys with aspirations of a lower cost processing route for such sheet product from powder. This will ultimately contribute to reduced fuel consumption and make air and space transport greener.

In this exciting EngD/PHD project, solid state powder routes, such as hot isostatic pressing and field-assisted sintering, will be used in conjunction with controlled hot and cold rolling to determine the effects of powder characteristics and alloy composition on the (1) hot rolling and thermomechanical processing characteristics and (2) microstructure and property development. In the first instance pack rolling in stainless steel packages and using heated rolls will be applied - to enhance the ductility, reduce oxidation and reduce cracking susceptibility. FE modelling software will be used to correlate thermomechanical processing, plane strain rolling parameters with microstructural evolution. Post hot rolling processing, such as cold rolling and superplastic forming will be related to the upstream powder-based, hot rolling route.