Calculation of the P-T phase diagram and tendency toward decomposition in equiatomic TiZr alloy.

Electronic, structural and thermodynamic properties of the equiatomic alloy TiZr are calculated within the electron density functional theory and the Debye-Grüneisen model. The calculated values of the lattice parameters a and c/a agree well with the experimental data for the α, ω and β phases. The ω phase is shown to be stable at atmospheric pressure and low temperatures; it remains energetically preferable up to T = 600 K. The α phase of the TiZr alloy becomes stable in the range 600 K < T < 900 K, and the β phase at temperatures above 900 K. The constructed phase diagram qualitatively agrees with the experimental data available. The tendency toward decomposition in the equiatomic alloy ω-TiZr is studied. It is shown that in the ground state the ω phase of the ordered equiatomic alloy TiZr exhibits a tendency toward ordering, rather than decomposition.