M. Kolb; J. M. Wheeler; H. N. Mathur; S. Neumeier; S. Korte-Kerzel; F. Pyczak; J. Michler; M. Göken
Materials Science and Engineering A 665 (2016) 135-140
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.