To study the influence of the microstructure on both the deformation mechanisms and mechanical properties of TiAl alloys at elevated temperatures, Ti-44Al (at%) alloy with a fully lamellar microstructure and Ti-47Al (at%) alloy with a duplex microstructure were prepared by adjusting the Al content. Hot compression tests at temperatures ranging from 600 ℃ to 1000 ℃ were performed on both the Ti-44Al and the Ti-47Al alloys. The analysis of the deformation mechanism reveals that nano-twinning is the dominant deformation mechanism of the γ phase. Nanoscale twins in a single γ phase traverse the whole γ phase grain, rather than becoming inhibited by the lamellar interfaces in the γ/α2 lamellar colonies. Thus, the length of nano-twins in a single γ phase is much longer than that in a γ phase lamella within γ/α2 lamellar colonies, resulting in a lower yield strength but better ductility. By increasing the loading temperature, the ductility of the γ/α2 lamellar colonies is markedly improved due to dynamic recrystallization (DRX), while the ductility of the single γ phase is improved by dislocations that traverse the twin boundaries at higher loading temperatures. Moreover, the effects of nano-twinning on the deformation and mechanical behaviours of TiAl alloys, especially at elevated loading temperatures, are discussed in detail.
Hao, yanjun, Liu, J., Li, S., Li, J., Liu, X., & Feng, X. (2017). Effects of nano-twinning on the deformation and mechanical behaviours of TiAl alloys with distinct microstructure at elevated loading temperatures. Materials Science and Engineering A, 705, 210–218. https://doi.org/10.1016/j.msea.2017.08.077