Gamma-titanium aluminides are showing great promise in high temperature applications, where their low density and high strength make them strong contenders for the manufacture of turbine blades, possibly supplanting the heavier nickel-based super alloys.
A range of alloy compositions are currently available, with compositions nominally similar to Ti-48Al-2Cr-2Nb that can be fabricated by additive layer manufacture (ALM) techniques. These techniques are related to the more familiar 3D printing technology. In ALM, thin layers of alloy powder are laid down, and selected areas are melted layer by layer using high powered lasers or Electron Beam Melting. As more layers are added, a 3D structure is gradually formed, embedded in a block of alloy powder. The unused powder is mechanically removed at the end of the process, to reveal the final manufacture.
Currently alloy formulations have been optimised for the traditional cast/wrought manufacturing route, and it is expected that improved formulations can be devised specifically for ALM using the techniques being developed by the DARE partnership. These techniques may increase our understanding of structure/property relationships for these alloys, and elucidate roles played by ‘impurities’, such as oxygen atoms. Recent studies suggest that these may be key to pinning dislocations in this family of alloys, and so play a vital role in determining their properties.