Phase transformations in the Al-Fe-Mo system

DOI: 10.62564/M4-IF1239

Iuliia Fartushna¹, Maryna Bulanova¹, Anatolii Samelyuk¹, Victor Vitusevych<sup>2

1</sup>Frantsevich Institute for Problems of Materials Science National Academy of Science of Ukraine
²ACCESS e.V., Germany


Introduction Fe3Al-based alloys are considered to be potential high-temperature structural materials due to their excellent resistance to thermal corrosion, high-temperature oxidation and sulfidation, combined with high strength, low density and comparably low cost. However, they have several disadvantages, such as low ductility at ambient temperatures and insufficient strength above 600°C. The addition of molybdenum increases the yield strength, tensile strength and resistance to wet corrosion [1, 2]. Methods Bulk metals of Al-99.995%, Fe-99.9%, Mo-99.9% were used to produce the ternary alloys. Alloys of 1-3 g were prepared by arc-melting under a purified Ar atmosphere (99.998%) using a non-consumable tungsten electrode on a water-cooled copper hearth. The samples were homogenized at 1450, 1300 and 1200°C during 30-100 h in a resistance furnace SShVL-0.6.2/16. The annealed alloys were then examined by scanning electron microscopy, electron probe microanalysis, and X-ray diffraction. Results Isothermal sections at 1450, 1300 and 1200°C have been determined experimentally for the first time in the entire range of compositions. The ternary intermetallic compound Al8FeMo3 (τ) with Al3Ti-type structure was observed at all investigated temperatures. It was shown that the (Mo) and (αFe) phases form the continuous solid solution (αFe,Mo) at 1450°C, which decomposes into (Mo) and (αFe) phases with the temperature decreases. The Fe7Mo6 (μ) phase, which in the binary Fe-Mo system is formed in solid state at 1368°C, extends into the ternary system up to 16 and 15 at.% at 1300 and 1200°C, respectively. Addition of Mo stabilizes the Al8Fe5 phase, and at 1300°C a narrow homogeneity region of this phase is present, the solubility of Mo in Al8Fe5 at 1200°C was measured as 14.4 at.%. The ternary Al-Fe-Mo and binary Al-Mo systems are thermodynamically re-modelled. The calculated phase diagrams are in good agreement with the corresponding experimental data.

Keywords
Isothermal section, Al-Fe-Mo, Ternary compound; CALPHAD modelling

Acknowledgments
Acknowledgments. The work was supported by the National Research Foundation of Ukraine (project no. 2021.01/0278).

References
[1] Liu Y., Zhang L., Cui S., Li W., Vacuum, 2021, 185, P. 110030. [2] Morris D.G., Munoz-Morris M.A., Chao J., Intermetallics, 2004, 12, P. 821-826.