Diagram of the phase composition of the Fe - Si - Al system and its isothermal sections

Diagram of the phase composition of the Fe - Si - Al system
and its isothermal sections

A. A. Akberdin, Dr. Eng., Prof., Head of the Bor laboratory;
A. S. Kim, Dr. Eng., Chief Researcher of the Bor laboratory;
A. S. Orlov, Dr. Eng., Senior Researcher of the Bor laboratory, e-mail: wolftailer@mail.ru;
R. B. Sultangaziev, Dr. Eng., Senior Researcher of the Bor laboratory

The diagram of the phase composition of the Fe – Si – Al system and its isothermal sections within the temperature
range of 300-3000 K are plotted. Thermodynamic data of Fe3Si, Fe2Si, Fe5Si3, FeSi, FeSi2 silicides, FeAl,
FeAl2, FeAl3, Fe2Al5 aluminides and Al2Fe2Si, Al3FeSi, Al2FeSi, Al11Fe3Si6, Al14Fe3Si3 ternary compounds are used.
The diagram consists of 20 elementary triangles of coexisting phases, the number of which decreases to 6 at the temperature
1900 K and more. At the temperatures above 2900 K, the equilibrium of the condensed phases is disturbed
due to the transition of such metal components of the low-melting aluminum corner of the diagram as Al, Al2, Fe, Si
and Si2, leading to losses of valuable elements, to the gas phase.
Crystallization fields are assessed by calculating the squares of elementary triangles, as well as the prevalence of each
compound in the phase space by taking into account its participation in the construction of adjacent triangles. Using
our own method, the mathematical model of the diagram was created in the form of equations for dependence of the
amount of the formed phase on the chemical composition of examined metal. The computer program was developed
based on the established equations. The examples of calculation of the phase composition of two grades of ferrosilicon
FeSi65 and FeSi75, which are the most common in metallurgy, as well as two grades of ferrosilicoaluminum
FeSi45Al15 and FeSi55Al20 are presented. Correspondence of the calculated and instrumentally found phase composition
of the industrial metal has been revealed. Presence of mathematical models makes it possible to accelerate
selection of the metal with the required composition and properties from the set of planned for smelting.
Key words: iron, silicon, aluminum, diagram, phases, thermodynamics, mathematical model.
DOI: 10.17580/cisisr.2022.01.14

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