Microstructure and mechanical properties of a high Nb-TiAl alloy with different carbon additions.

In this paper, the microstructure and mechanical properties of a high Nb-TiAl alloy with different carbon contents were characterized and measured, and the influence mechanisms of carbon addition were discussed. The results indicate that, the added carbon was first dissolved in alloy matrix and caused lattice distortion in α₂-TiAl and γ-TiAl. Exceeding its solid solubility, which was proved to be about 0.6 at%, the extra carbon was precipitated in the form of TiAlC. In addition, with the increasing of carbon content, the volume fractions of the α₂ phase and TiAlC enhancement phase increased, while the relative contents of γ phase and B2 phase decreased. Under the synergistic effects of phase composition, C solid solution strengthening, TiAlC precipitation strengthening and fine crystal strengthening, the high Nb-TiAl-0.6 C alloy exhibits the best overall performance, especially the high temperature compression performance. Compared with the original alloy without carbon addition, at 800 °C, its compressive stress increases from 900 MPa to 1074 MPa and compressive strain corresponding to the maximum compressive stress increases from 11.3 to 12.5% respectively.