1991 Volume 31 Issue 10 Pages 1212-1222
Possible pathways to mill production of gamma titanium aluminide based alloys are presented with the author's recent results on processing of the alloys. The focus is directed towards the fabrication into sheets by near-net-shaping and the thermomechanical processing for microstructure control. Developments in the alloying, processing, and microstructure controlling technology of titanium based and alpha-2 based alloys are surveyed to assess the opportunities for transfer of the current technology to alloy and process design of gamma based alloys, which may require more severe processing conditions to operate at elevated temperatures in a protective atmosphere and to work at low strain rates under application of high loads. Direct twin-roll casting has been demonstrated to be applicable to the experimental production of gamma alloy sheets. By optimum combinations with thermomechanical processing, macroalloying of beta stabilizing elements has been shown to produce a gamma plus beta microduplex structure that renders superplasticity. These laboratory tests suggest feasibility of the mill processing of gamma based alloys. However, tremendous gaps in both processability and performance are anticipated between laboratory products and mill products, making the transition of laboratory to commercial production more difficult than it has been for conventional alloys in the past. Highly extensive scientific and experimental bases should be established before gamma based alloys can be considered for the practical application in severe aerospace environments with satisfactory reliability and durability.
