An investigation of the origin of the superplasticity of cast TiAl alloys

Two high-Cr TiAl alloys, with different compositions of Ti–46Al–8Cr–2Nb–0.15B and Ti–46Al–8Cr–2Nb–0.5W–0.15B (at.%), were studied. Superplastic deformation was observed in these alloys in their cast conditions. The superplastic behavior was attributed to the development of a fine-grained microstructure containing a metastable β phase with heavy alloying of Cr. The fine-grained microstructure is favorable for the occurrence of grain boundary sliding, and the presence of the β phase and its transformation to γ phase during deformation are beneficial to stress relaxation and suppression of cavitation.