Phase equilibria in the Ti-Al binary system

I. Ohnuma, Y. Fujita, H. Mitsui, K. Ishikawa, R. Kainuma, K. Ishida

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232 Citations (Scopus)


New experimental results on the phase equilibria between the β-Ti (A2), α-Ti (A3), α2-Ti3Al (D019) and the γ-TiAl (L10) phases in the Ti-Al system using specimens with low levels of oxygen are presented. The results obtained on the α/γ and the α2/γ equilibria are in good agreement with the previous experimental and calculated phase boundaries, while the ones obtained on the α/β equilibrium deviate significantly from the previously proposed phase diagram. It is confirmed that the β phase field extends to higher aluminum contents and that the width of the α + β two-phase region is very narrow, less than 1 at.% Al. The presence of the A2/B2 order-disorder transition in the β phase is also confirmed by a combination of differential scanning calorimetric (DSC) analysis and extrapolation of ordering phase boundaries from the Ti-Al-X (X = Cr, Fe) ternary systems. A thermodynamic analysis has been carried out taking into account the ordering configurations in the β-Ti (A2)/β2-TiAl (B2), f.c.c.-Al (A1)/γ-TiAl (L10) and α-Ti (A3)/α2-Ti3Al (D019) equilibria. It is proposed that the anomalous α/β equilibrium is due to the A2/B2 ordering reaction.

Original languageEnglish
Pages (from-to)3113-3123
Number of pages11
JournalActa Materialia
Issue number12
Publication statusPublished - 2000 Jul 17

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys


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