NUST MISIS, Moscow, Russia

E. A. Naumova, Associate Professor of the Metal Forming Department, Candidate of Technical Sciences, e-mail: jan73@mail.ru
V. V. Doroshenko, Engineer of the Metal Forming Department, Candidate of Technical Sciences
N. O. Korotkova, Researcher of the Metal Forming Department, Candidate of Technical Sciences
A. I. Khabibulina, Master’s Student of the Metal Forming Department

Thermodynamic calculations, using Thermo-Calc software (TTAL5 database), and experimental methods were used to study a phase diagram of Al – Ca – Fe in the region rich in aluminum, including making a liquidus projection and a supposed distribution of phases in a solid state. The authors studied four hypereutectic Al – Ca – Fe alloys. The structure was studied with optical (OM, Axiovert 200 MAT) and scanning electron (SEM, TESCAN VEGA 3) microscopes equipped with an electron micro probe analyzer (EMPA, Oxford Instruments, Aztec software). It has been shown that instead of the Al3Fe phase in the equilibrium with a solid solution of aluminum (Al), the Al – Ca region of alloys should contain a triple combination, whose composition corresponds to the formula of Al₁₀CaFe₂. This combination, as well as the type and spacing of its crystalline lattice, were determined with X-ray phase analysis. A double compound is transferred to a triple compound during a peritectic transformation of L + Al₃Fe → (Al) + Al₁₀CaFe₂ (at 638 ^oC, 3.3% (at.) Ca and 0.5% (at.) Fe). Temperature of the non-variant peritectic transformation was specified during an original hardening experiment, involving soaking of the Al – 4% Ca – 3% Fe experimental alloy within 3 h at over 647 ^oC and below 623 ^oC in a liquid and solid state and its subsequent water quenching. Primary and eutectic crystals of such compound show compact morphology in contrast with acicular inclusions of the Al3Fe phase. They are included into a composition of disperse eutectic, therefore, alloys, which are close to a point of triple-phase eutectic in terms of their composition, are considered as promising casting compositions.
The research was funded by the Russian Science Foundation, project No. 20-19-00746-П.

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