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Phase Diagram Evaluations: Section II

Al-Ni-W (Aluminum-Nickel-Tungsten) V. Raghavan

The review of this ternary system by [2005Kor] included, among others, the studies of [1983Nas], [1991Udo], and [1994Jia]. Recently, [2008Pop] obtained new experimental data on the phase equilibria in Ni-rich alloys at 1100, 1000, and 900
C and computed three isothermal sections at these temperatures.

in the (c + c¢) region. The alloys were annealed at 1100, 1000, and 900
C for 10, 100, and 1300 h respectively and quenched in water. The phase equilibria were studied with scanning and transmission electron microscopy and energy

Binary Systems The Al-Ni phase diagram [1993Oka] shows five intermediate phases: NiAl3 (D011, Fe3C-type orthorhombic), Ni2Al3 (D513-type hexagonal, denoted d), NiAl (B2, CsCl-type cubic, denoted b), Ni5Al3 (Ga3Pt5-type orthorhombic), and Ni3Al (L12, AuCu3-type cubic, denoted c¢). The Al-W phase diagram [Massalski2] has at least three intermediate compounds: WAl4 (monoclinic, space group Cm), WAl5 (hexagonal, space group P63), and WAl12 (WAl12-type cubic). The details of other possible high temperature phases are not known. The Ni-W phase diagram [Massalski2] depicts three compounds: Ni4W (D1a, MoNi4-type tetragonal), NiW (MoNi-type orthorhombic), and NiW2 (tetragonal).

Ternary Isothermal Sections With starting metals of purity of 99.9-99.99%, [2008Pop] induction-melted under Ar atm three Ni-rich alloys that lie

Fig. 2 Al-Ni-W computed isothermal section at 1000
C for Ni-rich alloys [2008Pop]

Fig. 1 Al-Ni-W computed isothermal section at 1100
C for Ni-rich alloys [2008Pop]

Fig. 3 Al-Ni-W computed isothermal section at 900
C for Ni-rich alloys [2008Pop]

Journal of Phase Equilibria and Diffusion Vol. 30 No. 3 2009

281

Section II: Phase Diagram Evaluations dispersive x-ray analysis. Combining their new results with literature data, they optimized the thermodynamic interaction parameters using the CALPHAD approach. To account for the experimental results, [2008Pop] found it necessary to modify some of the thermodynamic parameters of [2001Dup] for Ni-base superalloys. The modified parameters were listed. The computed isothermal sections at 1100, 1000, and 900
C [2005Bro, 2008Pop] shown in Fig. 1-3 are compared with the experimental results. The agreement is satisfactory.

References 1983Nas: P. Nash, S. Fielding, and D.R.F. West, Phase Equilibria in Nickel-Rich Ni-Al-Mo and Ni-Al-W Alloys, Met. Sci., 1983, 17(4), p 192-194 1991Udo: A.L. Odovskii, I.V. Oldakovskii, and V.G. Moldavskii, Theoretical and Experimental Investigations of Phase Equilibria

282

in the Al-Ni-W System in the Range 900 to 1500
C, Metally, 1991, (4), p 112-123, in Russian; TR: Russ. Metall., 1991, (4), p 111-122 1993Oka: H. Okamoto, Aluminum-Nickel (Al-Ni), J. Phase Equilb., 1993, 14(2), p 257-259 1994Jia: C.C. Jia, K. Ishida, and T. Nishizawa, Partition of Alloying Elements Between c (Al), c¢ (L12) and b (B2) Phases in Ni-Al Base Systems, Metall. Mater. Trans. A, 1994, 25, p 473485 2001Dup: N. Dupin and B. Sundman, A Thermodyna