Phase equilibria among α (hcp), β (bcc) and γ (L1₀) phases in Ti-Al base ternary alloys

Phase equilibria between the α(A3), α₂(D0₁₉), β(A2 or B2) and the γ(L1₀) phases in the Ti-Al base ternary systems were investigated over the temperature range 1000-1300 °C. The tie lines and the phase boundaries were determined by electron probe microanalysis using multiphase alloys. It was established that almost all the elements except Zr tended to partition into the β phase rather than into the α, α₂ or the γ phase, while Zr mostly partitioned into the γ phase. At 1000 °C, in the equilibrium state between the α₂ and the γ phases. V, Cr, Mo, Ta and W partitioned to the α₂ phase rather than to the γ phase, whereas Mn, Fe, Co, Ni, Cu and Zr tended to concentrate into the γ phase. The partition coefficients for the alloying elements were only slightly dependent on their concentration. Based on these data, the relative stabilizing effects of alloying elements on the α, α₂, β and γ phases are discussed.