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

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.