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 degrees 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 (beta(0) -omega(0)) composite is the highest among all phases and remains constant with increasing temperature, thus the (beta(0)+omega(0)) 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 degrees C showed that the plastic deformation occurs mainly by < 111 > -type dislocations in the beta(0) phase. The high hardness of the (beta(0)+omega(0)) composite can be attributed to a hardening effect of coo precipitates. (C) 2016 Elsevier B.V. All rights reserved.