Processing issues in gamma titanium aluminides

Processing issues regarding two wrought and one cast alloy based on TiAl are discussed. Various analytical techniques were used to investigate the microstructural anomalies. In the wrought alloys, chemical segregation issues were the primary finding. Significant variances in grain size and local inhomogeneities in the microstructures due to insufficient distribution of alloying elements are discussed. The primary issues for the cast material were the formation of a thick columnar microstructure at the investment mold/metal interface and the presence of a large inclusion which had been liberated from the investment shell. Suggestions are given for improving the processing methods.