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Article Dans Une Revue Intermetallics Année : 1999

The ternary system Al-Ni-Ti Part II: Thermodynamic assessment and experimental investigation of polythermal phase equilibria

Résumé

The Al–Ni–Ti phase diagram has been thermodynamically assessed and a consistent set of thermodynamic functions has been developed. The thermodynamic modeling is based on an experimental investigation of the phase equilibria in the composition range of 0.1⩽xAl⩽0.7. Alloys were prepared by argon-arc or vacuum-electron beam melting of elemental powder blends. X-ray powder diffraction, metallography, SEM and EMPA-techniques were employed to analyze the samples in the as-cast state as well as after annealing at 800, 900 and 1000°C. The existence of the four ternary compounds, τ1 to τ4, has been confirmed, although homogeneity regions differ significantly from reports in the literature. The homogeneous phase, previously claimed at “Al23Ni26Ti51”, is shown by high resolution microprobe and X-ray diffraction measurements to be an extremely fine-grained eutectic structure. The congruent melting behavior of τ4=AlNi2Ti is confirmed, but, in contrast to earlier reports, primary crystallization and congruent melting have been observed for τ1=Al13Ni2Ti5 and τ3=Al3NiTi2. In contrast to earlier assessments, τ1,τ2 and τ3 are experimentally found to be stable at 800, 900 and 1000°C. The thermodynamic modeling of the ternary phases τ2 and τ3 is done with simplified sublattice models, considering their crystal structure and homogeneity ranges. The sublattice model for τ4 is taken from an earlier asessment of the nickel-rich ternary phase equilibria. The present assessment covers the entire composition range. An application to the solidification behavior of ternary alloys is also exemplified.
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hal-01007378 , version 1 (07-10-2017)

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Kejun Zeng, Rainer Schmid-Fetzer, Bertrand Huneau, Peter Rogl, Joseph Bauer. The ternary system Al-Ni-Ti Part II: Thermodynamic assessment and experimental investigation of polythermal phase equilibria. Intermetallics, 1999, 7 (12), pp.1347-1359. ⟨10.1016/S0966-9795(99)00055-2⟩. ⟨hal-01007378⟩
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