On the origin of superior high strength of Ti–45Al–10Nb alloys

The yield strengths of Ti–45Al–10Nb alloys with a near-gamma (NG) microstructure were measured at temperatures up to 900 °C. The NG Ti–45Al–10Nb alloys exhibited significantly higher yield strengths than conventional TiAl-base alloys with comparable microstructure. These high strengths appear to arise from the solid-solution hardening of Nb additions as concluded by comparing the friction stresses for TiAl alloys with and without Nb addition. The hardening effect of Nb additions was found to be dependent on the Al content of γ phase, being less significant in the γ phase containing higher aluminum. The origin of this dependence is postulated to be the varying site occupation of Nb in γ phase with different Al concentrations.