Phase equilibria in TiAl alloys containing 10 and 20 at% Nb at 1473 K

Abstract

Alloys with compositions around Ti-24Al-11Nb in the Ti-Al-Nb ternary system have been studied quite extensively because they constitute the base compositions of the super [alpha]2 titanium aluminides. In contrast to the above alloys, the [gamma] titanium aluminides containing niobium at the same concentration level have attracted less attention until quite recently. An earlier study on phase equilibria suggested the existence of an isolated ternary T[sub 2] phase field at a composition region around 45Ti-45Al-10Nb at 1,473 K. A recent investigation casts doubt on the existence of the T[sub 2] phase as an equilibrium phase. In this study, the phase equilibria of alloys with compositions around Ti-45Al-10Nb and Ti-40Al-20Nb have been examined to establish a [gamma] TiAl part of the isothermal section of the Ti-Al-Nb ternary system at 1,473 K.