Phase Equilibria in the Ternary Al–Ti–Pt System. I. Solidus Surface of the Al–Ti–Pt System in the Range 0–50 at.% Pt

The nature of phase equilibria has been examined for the first time in the Al–Ti–Pt system in the range 0–50 at.% Pt at subsolidus temperatures. Besides the τ1, τ2, and τ3 ternary compounds with AuCu3, Th6Mn23+1, and MgZn2 lattices known from the literature, eight more compounds form in the system at subsolidus temperatures. The structural type is known for three of these compounds. They are τ4 (ZrBeSi), τ5 (CrFe), and τ6 (defective structure of Au4Al type). There are 31 isothermal planes on the solidus surface. All planes are formed with participation of ternary compounds and solid solutions based on binary compounds present in the boundary systems. The highest temperature in this composition range corresponds to the congruent melting of the TiPt phase (1830°C) and the lowest to eutectic l ⇄ <Al> + <Al21Pt5> in the binary Al–Pt system (655°C).