The previous review of this ternary system by [2006Rag] presented a partial isothermal section at 1150 °C from the studies of [2005Hay]. Recently, new thermodynamic descriptions of this system were reported by [2009Lu] and [2010Zhu].

Binary Systems

The Al-Ni phase diagram [1993Oka] shows five intermediate phases: NiAl3 (D011, Fe3C-type orthorhombic), Ni2Al3 (D513-type hexagonal), NiAl (B2, CsCl-type cubic, also denoted β), Ni5Al3 (Ga3Pt5-type orthorhombic) and Ni3Al (L12, AuCu3-type cubic; denoted γ′). The Al-Pt phase diagram [1986McA] depicts nine intermetallic phases: Pt5Al21 (cubic), Pt8Al21 (tetragonal), PtAl2 (C1, CaF2-type cubic), Pt2Al3 (hexagonal), PtAl (B20, FeSi-type cubic), β (52-56 at.% Pt; B2-type cubic), Pt5Al3 (Ge3Rh5-type orthorhombic), Pt2Al (PbCl2-type orthorhombic above 1060 °C and Pt2Ga-type orthorhombic below 1060 °C), and Pt3Al (L12, AuCu3-type cubic and low-temperature Pt3Ga-type tetragonal). The Ni-Pt phase diagram [2009Lu] depicts a large region of the continuous face-centered cubic (fcc) solid solution of Ni and Pt. At low temperatures, three ordered phases appear Ni3Pt (L12, AuCu3-type cubic), NiPt (L10, AuCu-type tetragonal) and NiPt3 (L12, AuCu3-type cubic).

Computed Ternary Phase Equilibria

Using selected data on the experimental phase equilibria and the thermodynamic properties, [2009Lu] first assessed the Ni-Pt binary system with particular reference to the stability region of the three ordered structures Ni3Pt, NiPt and NiPt3. All the four fcc-based phases: the disordered fcc solid solution, Ni3Pt (L12), NiPt (L10) and NiPt3 (L12) were described using a four sublattice model. First-principles calculations were also performed to estimate the ground-state energies of the ordered compounds. The assessment of [2000Wu] of the Al-Pt system was modified by [2009Lu], using the four sublattice model for the fcc-based structures. First principles calculations were also carried out to determine the formation energies of the fcc-based structures as well as the B2 and B20 phases. The Al-Ni description by [2003Sun] was adopted by [2009Lu].

As in the binary systems, a four sublattice model was used to describe the fcc-based phase that forms within the ternary region or those that extend into the ternary region from the binary sides. The isothermal section at 1100 °C computed by [2009Lu] is shown in Fig. 1. The ternary phase AlNiPt2 (τ) [2005Hay] is present. The computed section was found to be in good agreement with the literature experimental data.

Fig. 1
figure 1

Al-Ni-Pt computed isothermal section at 1100 °C [2009Lu]

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With starting metals of purity of 99.95% or better, [2010Zhu] made 14 Ni-rich ternary alloys that fall in the two-phase region of (γ + γ′) or (γ′ + B2). The alloys were annealed at 1250 or 1160 °C for 30 days. The phase equilibria were studied with scanning electron microscopy and x-ray powder diffraction. The compositions of the co-existing phases were measured with an electron probe microanalyzer.

The cluster/site approximation was used to evaluate the thermodynamic parameters of the fcc-based phases. The liquid was described as a substitutional solution, taking into consideration the ternary interaction. The B2 phase was modeled using two sublattices, with all three elements residing in both sublattices. The optimized interaction parameters were listed. Two isothermal sections at 1250 and 1160 °C were calculated for Ni-rich alloys. These are shown in Fig. 2 and 3, along with experimental tie-lines [2010Zhu]. The agreement is satisfactory. The computed liquidus projection is shown in Fig. 4. The two liquidus lines depict a saddle-point minimum marked C1 and C2. There are no invariant reactions in this region of the system.

Fig. 2
figure 2

Al-Ni-Pt computed isothermal section at 1250 °C for Ni-rich alloys [2010Zhu]

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Fig. 3
figure 3

Al-Ni-Pt computed isothermal section at 1160 °C for Ni-rich alloys [2010Zhu]

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Fig. 4
figure 4

Al-Ni-Pt computed liquidus projection for Ni-rich alloys [2010Zhu]

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