Al-Co-Ni-Ti (Aluminum-Cobalt-Nickel-Titanium)

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Phase Diagram Evaluations: Section II

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

The phase equilibria between the B2 and L21 phases in this quaternary system was investigated by [2002Ish] and reviewed by [2005Rag]. Recently, [2008Cui] investigated the fcc-L12 relationships between 1100 and 750 C. The precipitation of disordered fcc particles in the L12 matrix has been studied in alloys of this quaternary system earlier, see for example [1997Liu].

Lower Order Systems Brief descriptions of the relevant binary systems can be found in [Massalski2]. Data on Al-Co-Ni, Al-Co-Ti, Al-Ni-Ti, and Co-Ni-Ti ternary systems were compiled by Villars et al. [1995Vil].

dispersive x-ray spectroscopy attached to the scanning electron microscope. In the phase equilibria of interest here, Co and Ni form a continuous face-centered cubic (fcc) solid solution c, which dissolves a few percent each of Al and Ti. The c¢ (L12) phases Ni3Al and Co3Ti form a continuous solid solution. The measured tie-line compositions between c (fcc) and c¢ (L12) at 1100 C are listed in Table 1 for the ﬁve quaternary alloys [2008Cui]. The (Ni + Co) content approximates to 75 at.% and (Al + Ti) content is 25 at.%, corresponding to the formula ðNi,CoÞ3 ðAl,TiÞ: Figure 1 shows schematically the phase relationships in a tetrahedron and is valid for the temperature range of 750 to 1100 C.

References

Quaternary Phase Equilibria [2008Cui] prepared ﬁve quaternary alloys by mixing two base alloys of Ni-Al and Co-Ti. The alloys were given a ﬁnal anneal of 32 h at 1100 C or 1000 h at 750 C: The phase equilibria were studied by scanning and transmission electron microscopy and x-ray powder diffraction. The compositions of the coexisting phases were measured by energy

1995Vil: P. Villars, A. Prince, and H. Okamoto. Handbook of Ternary Alloy Phase Diagrams, ASM International, Materials Park, OH, 1995, Al-Co-Ni: 3, p 3050-3063; Al-Co-Ti: 3, p 3074-3086; Al-Ni-Ti: 4, p 4195-4216; and Co-Ni-Ti: 7, p 8594-8596 1997Liu: W. Liu, H. Rosner, and E. Nembach, Search for c Precipitate Hardenable Quaternary L12-Ordered c¢ Intermetallics

Table 1 Measured tie-lines of Al-Co-Ni-Ti alloys at 1100 °C [2008Cui] Composition, at.% Phase/Alloy Alloy20(a) c (fcc) c¢ (L12) Alloy40(a) c (fcc) c¢ (L12) Alloy50(a) c (fcc) c¢ (L12) Alloy60(a) c (fcc) c¢ (L12) Alloy80(a) c (fcc) c¢ (L12)

Al

Co

Ni

Ti

14.5 14.6 18.1 11.1 12.4 14.2 9.3 9.4 11.2 7.6 8.2 8.9 3.7 5.0 4.7

15.1 18.9 12.4 30.8 33.2 26.7 38.7 44.1 33.7 46.7 50.5 42.7 63.1 69.6 61.8

66.5 63.6 64.8 50.5 47.5 49.8 42.4 39.0 43.6 34.1 31.6 35.3 17.4 13.1 15.4

3.8 2.9 4.7 7.6 6.9 9.3 9.6 7.5 11.5 11.6 9.7 13.1 15.8 12.4 18.0

(a) Alloy designations as used by [2008Cui]

Fig. 1 Al-Co-Ni-Ti schematic c (fcc) - c¢ (L12) equilibrium between 1100 and 750 C [2008Cui]

Journal of Phase Equilibria and Diffusion Vol. 30 No. 2 2009

199

Section II: Phase Diagram Evaluations with Compositions Around Ni3 ðAl,Si,TiÞ; ðNi,CoÞ3 ðAl,TiÞ and ðNi,CoÞ3 ðSi,TiÞ, Z. Metallkd., 1997, 88(8), p 648-651 2002Ish: K. Ishikawa, H. Mitsui

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