Phase Equilibria Investigations on the Aluminum-Rich Part of the Binary System Ti-Al

摘要

The binary system Ti-Al has been reinvestigated in the composition range of 50 to 76 at. pct Al by X-ray diffraction, metallography, electron probe microanalysis (EPMA), and differential thermal analysis (DTA). Heat-treated alloys (600 deg C to 1300 deg C) as well as the as-cast alloys were investigated. Seven stable intermetallic phases were observed: TiAl, Ti_(1-x)Al_(1+x), Ti_3Al_5, TiAl_2, Ti_5Al_(11), TiAl_3 (h), and TiAl_3 (l); two metastable phases, TiAl_2 (m) and TiAl_3 (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.