A study of the Al-Ni-Pt alloy system. Phase equilibria at 1100 and 1300°C

Abstract

UDC 669.762.295The Al-Ni-Pt phase diagram studied in the whole compositional region at 1300 and 1100°C. The Al 2 Pt phase found to extend up to at least Al 53 Ni 23 Pt 24 composition, separating the Al 3 Pt 2 and Al 3 Ni 2 phase fields. The Al-Ni β phase dissolves up to 38 at.% Pt at 1100°C, while at 1300°C the β region probably extends between the isostructural CsCl-type phases forming at the Al-Pt and Al-Ni terminals. The AlNi 3 phase (γ′) extends up to 35 at.% Pt at practically constant Al concentration, while the high-temperature AlPt 3 extends up to 15 at.% Ni. A ternary phase is formed in a wide compositional region between the regions of γ, γ′, β, and AlPt 3 . Apart from the AuCu-type structure of this ternary phase earlier reported, also its C-centered orthorhombic superstructure with a fourtimes larger unit cell revealed in the high-Al part of the compositional region.

A study of the Al-rich part of the Al–Ni–Pt alloy system

“…1c). The -phase was found in a compositional region maximally extended from Al 75 Ni 3 were established from the existence of the corresponding two-phase equilibria (see Fig. 1c).…”

“…1; for the comparison the relevant part of the diagram at 1100 • C is redrawn from Ref. [3] in Fig. 1a).…”

Influence of the superalloy substrate in the synthesis of the Pt-modified aluminide bond coat made by slurry

“…The cracks can be associated with the intrinsic brittleness of the Ni 2 Al 3 matrix [32] and of the PtAl 2 precipitates that lower the toughness of the aluminides [33]. The presence of PtAl 2 is often observed at higher temperatures [11,34] although the equilibrium phases reported at 790°C were Al 4 Pt and Al 21 Pt 8 [35]. Therefore, the formation of PtAl 2 could result from the local increase of temperature due to the strong exothermic reactions upon aluminizing [36] but the presence of PtCr cannot be ruled out [29].…”

Diffusion behaviour of Pt in platinum aluminide coatings during thermal cycles

“…4) [22], the area around Al 2 NiPt is called the b* superstructure, which is cubic with a lattice parameter twice that of the b-phase and is built in a similar way to PtAl 2 [23]. However, there is a difference between PtAl 2 and b*: the 4b Wyckoff positions in PtAl 2 are vacant, while they are occupied by Ni in b* [22,24]. The shift from Al 2 Pt to b* observed in the XRD patterns is consistent with the gradual filling of the vacant positions by Ni.…”