Hot working behavior and processing map of a γ-TiAl alloy synthesized by powder metallurgy

Powder metallurgy technique has been explored to synthesize a titanium aluminide alloy with the composition 46Ti–46Al–4Nb–2Cr–2Mn by mixing of elemental powders followed by hot isostatic pressing (HIP). The microstructure of the compact revealed the formation TiAl solid solution in addition to a Nb-rich phase. Cylindrical specimens from the HIP’ed billets were compressed at temperatures and strain rates in the ranges of 850–1050 °C and 0.0001–10 s−1. A processing map has been developed on the basis of flow stress data at different temperatures and strain rates, which revealed that the alloy may be hot worked in the range 925–1050 °C and 0.0001–0.01 s−1. Kinetic analysis of the flow stress data yielded a stress exponent of 4.4 and apparent activation energy of 387 kJ/mole which is close to that for self-diffusion of Al in γ TiAl.

► A γ TiAl alloy is prepared by blending and hot isostatically pressing elemental powders.
► γ TiAl, ordered Nb in γ TiAl phase, and a Nb-rich intermetallic compound are present.
► The processing map exhibits two domains representing dynamic recrystallization of γ TiAl.
► Activation energy of 387 kJ/mole was obtained which is similar to self diffusion of Al in γ TiAl.