Proper (Nb,Fe) co-alloyed TiAl-based alloy with good hot deformation processing capability

Abstract

In order to develop a proper (Nb,Fe) co-alloyed TiAl-based alloy with excellent hot deformation processing capability, avoiding the heavy alloying induced damage of service properties, the Ti–44Al–4Nb-0.5Fe-0.1B and Ti–44Al–2Nb–2Fe-0.1B alloys are designed and prepared. This paper mainly focuses on whether and why the hot deformation processing capability of the new alloys are improved. In view of this, thermo-compression experiments are carried out, hot deformation behavior is studied, constitutive equations are derived, hot processing maps are drawn, and hot deformation microstructure is studied. The results show that the Ti–44Al–2Nb–2Fe-0.1B alloy has lower true stress, moderate diffusion activation energy, lower stress exponent and larger hot processing window. Especially, the large hot processing window of Ti–44Al–2Nb–2Fe-0.1B alloy covers almost all the tested range of 1100 °C–1250 °C and 0.001 s−1-1.0 s−1, and meanwhile, the its power dissipation factor is higher. At lower temperatures of 1100 °C and 1150 °C, relatively more B2 phase in the Ti–44Al–2Nb–2Fe-0.1B alloy plays a good stress-strain coordination effect in the hot deformation process. At higher temperatures of 1200 °C and 1250 °C, the Ti–44Al–2Nb–2Fe-0.1B alloy is in the higher temperature phase region. Moreover, the compressed Ti–44Al–2Nb–2Fe-0.1B alloy has relatively lower dislocation density and more adequate dynamic recrystallization. In conclusion, all these results demonstrate that the Ti–44Al–2Nb–2Fe-0.1B alloy meets the design expectations, that is, this alloy with a proper (Nb,Fe) addition still has a very good hot deformation processing capability. At the same time, the Ti–44Al–2Nb–2Fe-0.1B alloy has a typical near-lamellar structure, rather than containing too much B2 phase or even containing lots of τ2 phase, so the good service properties can be expected.