Phase equilibria investigations on the aluminum-rich part of the binary system Ti-Al

The binary system Ti-Al has been reinvestigated in the composition range of 50 to 76 at, pet Al by X-ray diffraction, metallography, electron probe microanalysis (EPMA), and differential thermal analysis (DTA). Heat-treated alloys (600 degreesC to 1300 degreesC) as well as the as-cast alloys were investigated. Seven stable intermetallic phases were observed: TiAl, Ti1-xAl1+x, Ti3Al5, TiAl2, Ti5Al11, TiAl3 (h), and TiAl3 (l); two metastable phases, TiAl2 (m) and TiAl3 (m), were also found. For each of these phases, the homogeneity range and the crystal chemical parameters were determined. The temperatures of the solid-state phase reactions were re-established. On the basis of the experimental results, an improved version of the equilibrium phase diagram has been drawn and critically compared with earlier versions presented in the literature.