Local mechanical properties of the (β0+ω0) composite in multiphase titanium aluminides studied with nanoindentation at room and high temperatures

Kolb, M.; Wheeler, J. M.; Mathur, H. N.; Neumeier, S.; Korte-Kerzel, S.; Pyczak, F.; Michler, J.; Göken, M.

Materials Science and Engineering A 665 (2016)

High temperature nanoindentation was conducted on a Ti-44.5Al-6.25Nb-0.8Mo-0.1B (in at.%) alloy from room temperature up to 600 °C to determine the temperature dependence of the local mechanical properties of the individual phases in a multiphase titanium aluminide alloy. The hardness of the (β0+ω0) composite is the highest among all phases and remains constant with increasing temperature, thus the (β0+ω0) composite does not decrease the strength of the alloy even at near service temperatures. A Burgers vector analysis in TEM of the deformed volume under the residual imprints after indentation at room temperature and 600 °C showed that the plastic deformation occurs mainly by <111>-type dislocations in the β0 phase. The high hardness of the (β0+ω0) composite can be attributed to a hardening effect of ω0 precipitates.