The ternary orthorhombic so-called O-phase occurs in highly alloyed γ-TiAl-based alloys for high temperature applications. While some investigations exist about Ti2AlNb based O-phase, results for compounds replacing Nb with other alloying elements from V and VIB group are scarce. We present a comprehensive first-principles density functional theory study to assess the effects of alloying elements M = V, Nb, T, Mo and W, on the properties of the ternary Ti2AlM orthorhombic O-phase. Properties calculated include phase stability as well as structural, electronic and mechanical properties. To get an insight into finite-temperature properties, the vibrational contribution to Helmholtz free energy is described by either calculating full phonon spectra or the Debye–Grüneisen model and the thermal electronic contribution is estimated from the integration over the electronic density of states.

Important results are that all Ti2AlM compounds are stable according to formation energy and mechanical and dynamical stability. With respect to the energy of formation, Ti2AlMo was found to be the most stable compound and the aforementioned results can be interpreted as effects of electronic bonding and dynamical properties of the different compounds.