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hase Diagram Evaluations: Section II

Al-Ni-Ti (Aluminum-Nickel-Titanium) V. Raghavan

tetragonal, denoted c), Ni2Al3 (D513-type hexagonal), and NiAl (B2, CsCl-type cubic).

The update of this system by [2005Rag] reviewed the results of [1999Hun] (experimental isothermal section at 900 °C) and of [1999Zen] (computed liquidus surface and computed isothermal sections at 1200, 900 and 800 °C). Following a critical review of this system by [2006Sch], [2007Sch] presented new experimental results on the liquidus surface and isothermal sections at 1000 and 900 °C. These results were reviewed briefly by [2009Rag]. A more recent publication by [2009Bur] reported several three-phase equilibria at 1050 °C in the central part of the composition triangle, where the ternary phases lie.

Ternary Phases The ternary phases in this system which have been reviewed in earlier reports are: s1 (nominal composition Al13Ni2Ti5; AuCu3-type cubic), s2 (Al2NiTi; Mn23Th6-type cubic), s3 (AlNiTi; MgZn2-type hexagonal), s4 (AlNi2Ti; AlCu2Mn-type cubic), and s5 (Al65Ni20Ti15; unknown structure).

Binary Systems

Partial Isothermal Section at 1050 °C

The intermediate phases in the three binary subsystems were summarized by [2009Rag]. The binary compounds that are present in the partial isothermal section at 1050 °C determined by [2009Bur] are: TiAl (L10, AuCu-type

With starting metals of 99.9995% Al, 99.99% Ni and 99.99% Ti, [2009Bur] induction-melted under Ar atm eight ternary alloys in the central region of the composition triangle. The alloys were annealed at 1050 °C for 70 h and

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Atomic Percent Nickel Fig. 1 Al-Ni-Ti partial isothermal section at 1050 °C [2009Bur]

Journal of Phase Equilibria and Diffusion Vol. 31 No. 1 2010

55

Section II: Phase Diagram Evaluations quenched in water. The phase equilibria were studied by metallography, electron back-scatter diffraction and energy dispersive x-ray analysis. The tie-triangles determined by [2009Bur] at 1050 °C are shown in Fig. 1. They are the same as those determined by [2007Sch] at 1000 °C. The compositions of the coexisting phases are also close to the values determined by [2007Sch]. While confirming the existence of the s5 phase, [2009Bur] discounted the possibility of its being a decagonal phase. The structure of s5 still remains unknown.

References 1999Hun: B. Huneau, P. Rogl, K. Zeng, R. Schmid-Fetzer, M. Bohn, and T. Bauer, The Ternary System Al-Ni-Ti: Part I. Isothermal

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Section at 900 °C; Experimental Investigation and Thermodynamic Calculation, Intermetallics, 1999, 7, p 1337-1345 1999Zen: K. Zeng, R. Schmid-Fetzer, B. Huneau, P. Rogl, and J. Bauer, The Ternary System Al-Ni-Ti: Part II. Thermodynamic Assessment and Experimental Investigation of Polythermal Phase Equilibria, Intermetallics, 1999, 7, p 1347-1359 2005Rag: V. Raghavan, Al-Ni-Ti (Aluminum-Nickel-Titanium), J. Phase Equilb. Diffus., 2005, 26(3), p 268-272 2006Sch: J.C. Schuster, Critical Data Evaluation of the Aluminum-Nickel-Titanium System,