Experimental Investigation of the Influence of Phase Compounds on the Friability of Fe-Si-Mn-Al Complex Alloy

Abstract

The research presented in the article is devoted to the study of the influence of phase compounds on the friability of the Fe-Si-Mn-Al complex alloy. The urgency of the problem lies in the development of technology for producing a non-scatterable alloy from manganese-containing ores and high-ash coals. The main goal of this work is to determine the range of alloy compositions and the resulting phases that affect the dispersibility of the alloy, which is critically important for its industrial implementation. Research methods include thermodynamic diagram analysis (TDA) using data on the standard enthalpy of formation of intermetallic compounds, as well as experimental tests in an ore-thermal electric furnace with a capacity of 200 kV*A. The results show that Fe-Si-Mn-Al complex alloys form a variety of silicide and aluminide phases, including intermetallic compounds and ternary systems, which is critical for understanding and controlling their physicochemical properties. When melting a complex alloy, the content of leboite (Fe₃Si₇) in the Fe-Si-Mn-Al system plays a significant role. The development of melting process technology will be aimed at avoiding the FeSi₂-Fe₃Si₇-F₂(FeAl₃Si₂)-Mn₁₁Si₁₉ tetrahedron area. This approach to controlling the composition of a complex alloy is critical to ensuring its consistent friability properties in industrial applications. Thus, this work represents an important step in understanding the physical properties and stability of Fe-Si-Mn-Al complex alloys, which have potential for widespread use in metallurgical and other industrial applications.

1. Introduction

Complex alloys used for steel processing have a high application potential from the standpoint of reducing costs and improving the quality characteristics of steel products. Treatment of steel deoxidation with alumosilicomanganese (AMS) complex alloy makes it possible to obtain steel with a low content of non-metallic inclusions compared to deoxidation with traditional deoxidizers [1].

Today, scientists from Kazakhstan are actively developing and improving the technology for producing a complex alloy of aluminum-silicon-manganese (AMS) involving substandard manganese-containing ores and high-ash coals. Despite the positive results of many years of research, the industrial development of the melting process of AMS alloy is hampered due to self-destruction and dispersion of the alloy of various chemical compositions.

The AMC alloy first cracks and then crumbles to a powdery state. The main reason for disintegration is deliberate volumetric changes during crystallization of the alloy. Researchers specify that the tendency for the alloy to disintegrate appears with the simultaneous presence of phosphorus (max. 0.048%) and aluminum [2,3].

As proposed in [4,5,6,7], there are various reasons for the disintegration of ferroalloys, for example, in ferromanganese—impermanence of manganese carbide or the presence of aluminum, and in a ferrosilicon alloy—volumetric phase changes during crystallization and formation of the alloy.

Analysis of scientific research works on the study of the physical properties of the alloy (propensity to disintegrate, melting point, density), the authors [2,5,6,7] provide the following data: AMS alloys containing 60–70% manganese, 5–15% silicon, 8–20% aluminum, and carbon from 0.4 to 2%, with a total aluminum and silicon content not higher than Σ_Si+Al = 22–23%, are quite strong and at the same time easily crushed, i.e., convenient to use. Alloys with a high total content of aluminum and silicon (>30%) are very fragile. As the carbon content increases, they crumble more easily. The tendency of AMS alloys to crumble decreases when they contain 40–50% manganese, 10–20% silicon, 8–10% aluminum, and 0.75–1.0% carbon. The total content of silicon and aluminum was Σ_Si+Al = 19–30%. In alloys with a high content of silicon 30–50% and manganese 30–40%, aluminum 10%, and carbon 0.6–0.75%, the tendency to disintegration increases with increasing content of silicon and manganese. The phosphorus content in all groups of alloys was 0.1–0.2%. In all the studied alloys, a tendency to disintegration was observed. The disintegration of the AMS alloy was also studied more deeply in the works of Medvedev G., Takenov T., Radugin V., and Tolstoguzov N. [2]. It is indicated that the AMS alloy with a silicon content of more than 30%, aluminum above 3%, and phosphorus above 0.05% crumbles into powder when stored in air due to the interaction of phosphides and carbides with air moisture.

The relevance of this study is due to the need to develop a sustainable technology for producing complex alloys with specified properties that could be widely implemented in industrial production. In particular, complex alloys such as aluminum-silicon manganese (AMS) are widely used in the metallurgical industry, especially in steel processing, where their use allows achieving a lower content of non-metallic inclusions than with traditional deoxidation methods. However, despite significant success in laboratory and experimental studies, the introduction of AMS into industrial production is limited by the problem of self-destruction and crumbling of the alloy. This phenomenon, caused by volumetric changes during crystallization and chemical impermanence of the phases, leads to a decrease in the strength of the alloy and limits its use.

For this purpose, it is necessary to study in detail the relationship between the phase composition of the alloy and its chemical composition, which will identify critical areas that contribute to crumbling.

To identify the causes of self-destruction of individual compositions of the AMS alloy, a complete picture of the relationship between the phase compositions of the alloy depending on the chemical composition is necessary. The objective of this study is a detailed inquiry of phase compounds in the Fe-Si-Mn-Al system in order to identify critical areas of compositions that promote alloy disintegration. To achieve this goal, thermodynamic diagram analysis (TDA) was used, which allows for determine the set of possible phases and intermetallic compounds depending on the chemical composition of the alloy. Determination of phase crystallization areas that affect the alloy’s tendency to self-destruction is a key step in developing methods for controlling its phase composition and, consequently, improving its performance characteristics. The results of this study will be of significant importance for improving the production technology of complex alloys based on the Fe-Si-Mn-Al system, which ultimately contributes to their widespread introduction into metallurgy and other industrial sectors.

2. Materials and Methods

In literary reference books and electronic databases there is a lot of link data on the Gibbs energies of formation of iron and manganese silicides and iron and manganese aluminides, as well as information on ternary compounds. These data are often contradictory, and for some compounds they are completely absent. The value of ΔG°₂₉₈ for complex ternary compounds of the metal system Fe-Si-Mn-Al is not available in the literature [8,9,10,11,12,13,14,15,16,17,18,19].

To reduce the calculation error in this work, in the thermodynamic diagram analysis, instead of ΔG°₂₉₈, only the values of the enthalpies of formation of intermetallic compounds were used, since in the calculations the influence of the entropies ΔS°₂₉₈ at standard temperature is insignificant—ranging from 0.53% to 3, 41% (

Table 1. An example of the difference between ΔH°₂₉₈ and ΔG°₂₉₈, % [18].

№	Formula	ΔH°298, kJ/mol	ΔS°298, J/mol	ΔG°298, kJ/mol	Difference between ΔH°298 and ΔG°298, %	Melting Point
1	FeSi (66.6/33.3)	−78.85	44,685	−78,430	0.53	1683 K
2	FeSi2 (50/50)	−81.17	55,647	−78,405	3.41	1493 K
3	Fe3Si (85.7/14.3)	−93.72	103,596	−94,597	0.92	1813 K
4	Fe5Si3 (76.9/23.1)	−244.35	209,618	−249,343	2.0	1373 K

). Based on this, we believe that using the values of the standard enthalpy of formation will be sufficiently reliable to carry out a thermodynamic diagram analysis of the Fe-Si-Mn-Al system in relation to a temperature of 298 K.

The following systems were considered at a temperature of 298 K: Fe-Si, Fe-Mn, Fe-Al, Mn-Si, Al-Si, and Al-Mn [8,9,10,11,12,13,14,15,16,17]. Some phases of double compounds, such as Mn₉Si₂, Mn₁₁Si₁₉, Mn₄Al₁₁, and MnAl, as well as ternary compounds of the Fe-Al-Si and Si-Mn-Al systems, which are given in the literature, were calculated by us using the method of thermodynamic additivity of enthalpies of similar compounds (marked with «*»).

For example, the value of ΔH°₂₉₈ (Mn₁₁Si₁₉) is calculated as follows:

ΔH°₂₉₈ (Mn₁₁Si₁₉) = 8 × ΔH°₂₉₈ (Mn₂Si₃) − 5 × ΔH°₂₉₈ (MnSi) = 8 × (−164.90) − 5 × (−77.82) =
= −930.1 kJ/mol.

ΔH°₂₉₈(Fe₅Al₈Si₇) = ΔH°₂₉₈ (Fe₂A_l5) + ΔH°₂₉₈ (FeAl₃) + 5 × ΔH°₂₉₈ (FeSi₂) − 3 × ΔH°₂₉₈ (FeSi) =
= ((−200.0) + (−111.63) + 5 × (−81.17)) − 5 3 × (−78.85) = −480.93 kJ/mol

We believe that this method is reliable due to the fact that the calculations used data from the link database of double compounds [18], which together significantly reduces the level of relative errors.

The breakdown of the Fe-Si-Mn-Al system into a set of stable coexisting triangles of compounds was carried out according to the method described in [20], where the method of exchange reactions of 4 closest compounds was used. In this case, the reaction between the components is composed as the sum of two compounds located opposite each other along diagonals from selected four points.

The method for compiling exchange reactions is based on the well-known Hess equation: ∆H°₂₉₈ reaction = Σ∆H°₂₉₈ (product) − Σ∆H°₂₉₈ (starting substance), i.e., the value of the standard enthalpy is equal to the difference between the sum of the enthalpies of the reaction products and the sum of the enthalpies of the starting substances. As a result of calculating the reaction, if the standard enthalpy of the reaction has a positive value, then a line is drawn between the initial components (reaction products are not formed); if the calculation results in a negative value ΔH°₂₉₈, then the line is drawn between the product reactions. As a result of calculations of possible reactions and the determination of stable paired compounds, the system is divided into many stable triangles of coexisting phases.

An example of calculation of equations is given in relation to the triangulation option for the Fe-Al-Mn system:

2MnAl₃ + 4FeAl₃ = 2MnAl₄ + 2Fe₂Al₅

ΔHr = (2 × (−101.6) + 4 × (−111.63)) − (2 × (−104.4) + 2 × (−200.0)) = 40.92 kJ (draw a stable secant 2MnAl₃ + 4FeAl₃).

We verified the substantiation of the theoretical data obtained under experimental conditions using a large laboratory ore-thermal electric furnace with a transformer power of 200 kVA. The diameter of the graphite electrode is 150 mm. The electric furnace is two-electrode with a conductive hearth, and one electrode is coked in the hearth with the hearth mass. The electric furnace has a structure similar to the Mige type electric furnace [21,22,23]. The diameter of the furnace bath is 550 mm, and the depth of the bath is 400–450 mm. The hearth of the furnace was made of carefully compacted and electrically conductive hearth mass. The transformer is powered by a voltage of 380 V. The electric furnace is equipped with four stages of secondary voltage regulation—from 18.4 to 49 V. The charge cone around the electrode was 0.3–0.45 m at an angle of 35–40°. The electric melting mode was chosen in such a way as to create the necessary temperature conditions in the shaft with deep seating of the electrodes; the current intensity on the low side is from 2400 to 2800 A.

Manganese ore, high-ash coal, and quartzite were used as raw materials for the melting process of the AMS alloy. Coke was not used due to the sufficient carbon content of coal.

The technical and chemical composition of the charge materials are presented in

Table 2. Technical composition of high-ash coal from the «Saryadyr» deposit.

Adry	Vdry	W	Csolid
50.04	19.28	1.98	31.86

and

Table 3. Chemical composition of charge materials.

Material	Fe2O3	SiO2	Al2O3	MnO2	CaO	MgO	TiO2	P2O5	S	Ignition Losses
Mn ore	5.72	6.27	0.72	49.94	15.05	0.83		0.02	0.01	21.44
Coal ash	5.79	66.36	20.7		2.64	3.46	1.01	0.035	0.005
Quartzite	0.52	95.57			0.24	0.12			0.01	3.54

.

In order to study the phase composition of the Fe-Si-Mn-Al complex alloy, an X-ray phase assessment was carried out. The X-ray phase analysis was carried out on an XRD 7000c X-ray diffractometer (Shimadzu, Kyoto, Japan) with a set of high and low temperature chambers and a polycapillary optics system at the Federal State Budgetary Scientific Institution «Institute of Metallurgy, Ural Branch of the Russian Academy of Sciences» (Yekaterinburg, Russian Federation).

For the analysis, powder samples of the alloy were prepared, ground, and thoroughly mixed homogeneously to obtain the random orientation of the crystallites. The samples were placed on glass substrates and irradiated with X-rays using a copper anode Cu Kα (λ = 1.5406 Å) at a voltage of 40 kV and a current of 30 mA.

Scanning was performed in the 2θ range from 10° to 90° with a step of 0.02° and an exposure time of 0.5 s per step. The resulting diffraction patterns were analyzed using data processing and phase identification software, which allowed the determination of the phases present and their relative amounts in the sample.

The phases were identified by comparing the experimental data with the PDF (Powder Diffraction File) database data. To clarify the phase composition and component distribution, Rietveld analysis methods were used, which allow us to evaluate not only the qualitative but also the quantitative composition of the phases.

3. Results

The study of the Fe-Si-Mn-Al system is one of the important tasks for obtaining an alloy with specified properties and characteristics, as well as for a correct understanding of the phase composition of the alloy at various ratios of iron, silicon, manganese, and aluminum. In the Fe-Si-Mn-Al system, it is necessary to analyze 6 binary systems: Fe-Si, Fe-Mn, Fe-Al, Mn-Si, Al-Si, and Al-Mn and 4 ternary systems: Fe-Si-Al, Si-Mn-Al, Fe-Mn-Si, and Al-Mn-Si. All binary systems have been studied by numerous scientists [8,9,10,11,12,13,14,15,16,17,18,19], and the phase diagrams are detailed.

In the system under consideration, one of the most common systems in the ferroalloy industry is the Fe-Si system. Melts of the Fe-Si system have been widely studied both experimentally and using various model representations. This allows them to be used as basic objects when testing new models and developing new methods for determining the thermodynamic properties of alloys.

More than 70 works of scientists around the world are devoted to the study of the state diagram of the Fe-Si system. In the alloys of the system, the existence of iron-based silicon solid solutions (γ-Fe and α-Fe), as well as intermetallic phases Fe₂Si(β), Fe₅Si₃(η), FeSi(ε), FeSi₂(NT) and FeSi₂(VT) were discovered, which are presented in review papers [8,9,10,11,12,13,14,15,16,17,18,19].

In the practical use of ferrosilicon, it was found that alloys containing atleast 33.3% silicon are subject to dispersion. All alloys of this composition contain a ξ-phase—leboite, a phase of variable composition with a silicon content in the range of 52–58%, named «Leboit», at the suggestion of Kurnakov, in honor of the French scientist Lebo. This phase has two modifications: a high-temperature modification ξα and a low-temperature modification ξβ, which is similar in composition to the FeSi₂ compound, as follows from works [24,25].

It has been established that alloys containing the ξ-phase in the presence of aluminum, phosphorus, and calcium additives are subject to disintegration. According to the authors, a necessary circumstance is that the alloys tend to fracture only in the simultaneous presence of aluminum and phosphorus, which is explained by the skill of aluminum and phosphorus, when dissolved in leboite, to form a quaternary solution of Fe-Si-P-Al. The solution, when exposed to air moisture, disintegrates with the release of hydrogen phosphide.

The decomposition of leboite is accompanied by a significant increase in its volume and is the cause of internal stresses that contribute to the disintegration of ferrosilicon. As the composition of the alloy moves away from the leboite phase (both in the direction of decreasing silicon content and in the direction of increasing it), the resistance of ferrosilicon increases, which is explained by a decrease in the amount of leboite in the alloy.

From the analysis of the phase diagram of the state of the Fe-Si system [8,9,10,11,12,13,14,15,16,17,18,19], it follows that at a temperature of 298 K there are 5 intermetallic phases in the system: Fe₃Si, Fe₅Si₃, FeSi, FeSi₂, and Fe₃Si. The initial data for the standard enthalpies of the Fe-Si system for thermodynamic diagram analysis are presented in

Table 4. ΔH°₂₉₈ value for compounds of Fe-Si, Fe-Al, Mn-Si, and Al-Mn systems [18].

№	Formula	Ratio, Mass%				ΔH°298, kJ/mol
		Fe	Si	Mn	Al
1	Fe3Si	85.64	14.36			−93.72
2	Fe5Si3	76.82	23.18			−244.35
3	FeSi	66.54	33.46			−78.85
4	FeSi2	50.15	49.85			−81.17
5	FeSi3	53.99	46.01			−154.45
6	Fe3Al	86.13			13.87	−62.00
7	FeAl	67.42			32.58	−50.21
8	FeAl2	50.86			49.14	−78.45
9	Fe2Al5	45.29			54.71	−200.00
10	FeAl3	40.83			59.17	−111.63
11	Mn6Si		7.85	92.15		−101.90
12	* Mn9Si2		10.20	89.80		−322.46
13	Mn3Si		14.56	85.44		−123.85
14	Mn5Si3		23.47	76.53		− 200.83
15	MnSi		33.83	66.17		−77.82
16	Mn2Si3		43.40	56.60		−164.90
17	* Mn11Si19		46.89	53.11		−981.35
18	MnAl6			25.34	74.66	−110.00
19	MnAl4			33.73	66.27	−104.40
20	MnAl3			40.43	59.57	−101.60
21	* Mn4Al11			42.54	57.46	−358.70
22	* MnAl			67.06	32.94	−96.00

* ΔH°₂₉₈—determined by additivity method.

(positions 1–5).

The phase diagram of the Fe-Al system is a component of ferrosilicoaluminum and ferroaluminum alloys. A large number of studies have been devoted to the Fe-Al phase diagram [8,9,10,11,12,13,14,15,16,17,18,19,24,25]. The system includes five stable phases, namely: Fe₃Al, FeAl₂, FeAl, Fe₂Al₅, FeAl_3, and limited solid solutions on both the Fe and Al sides, each of which has its own homogeneity region (Table 4 (positions 6–10)).

A large number of works have been devoted to the Mn-Si phase diagram, as well as the above-mentioned phase diagrams; the most complete data are given in [1,8,9,10,11,12,13,14,15,16,17,18,19,26].

There are seven intermetallic phases of these in the system: Mn₅Si₃ and MnSi melt congruently at temperatures of 151.2 and 1542 K, respectively; ν(Mn₉Si₂), Mn₃Si, and Mn₁₁Si₁₉ are formed by peritectic reactions, R(Mn₆Si) and Mn₅Si—by peritectoid reactions. In addition, Mn₃Si undergoes a polymorphic transformation at a temperature of 950 K.

The initial values of enthalpies of formation for manganese silicides, Mn₆Si, Mn₉Si₂, Mn₃Si, Mn₅Si₃, MnSi, Mn₂Si_3, and Mn₁₁Si_19, were taken from [1] as the most reliable ones (Table 4, positions 11–17).

The Al-Mn phase diagram is based on the results of the work of scientists given in [8,9,10,11,12,13,14,15,16,17,18,19,27,28,29,30,31]. The initial values of the standard enthalpies of formation of manganese aluminides—MnAl₆, MnAl₄, MnAl₃, Mn₄Al₁₁, and MnAl were taken from the most reliable ones (Table 4, positions 14–18).

A large number of studies have been devoted to the Al-Si phase diagram, a review of which was made in [8,9,10,11,12,13,14,15,16,17,18,19]. There are no intermetallic compounds in the Al-Si system, and a solid solution is formed throughout the composition. This system belongs to the ordinary eutectic type with low solubility of the components in each other in the solid state. Numerous results from various studies are in good agreement with each other. At a content of 12.3–12.7%, there is a eutectic with a melting point of 850.2 K.

Information on the Fe-Mn phase diagram is given in [8,9,10,11,12,13,14,15,16,17,18,19] and reviewed in [12]. It has been established that two peritectic invariant transformations occur in the alloys of the system. Calculation of the Fe-Mn phase diagram based on the thermodynamic properties of individual alloys of this system showed its good agreement with the diagram constructed from experimental data [32,33]. There are no chemical intermetallic compounds in the Fe-Mn system.

Ternary compounds in the Fe-Si-Mn-Al system have practically not been studied in relation to complex alloys. Scientific publications regarding this system are mainly devoted to aluminum coal with an aluminum content of more than 75–80%. As noted above, the Fe-Si-Mn-Al metal system consists of 4 ternary systems: Fe-Si-Al, Si-Mn-Al, Fe-Si-Mn, and Fe-Mn-Al.

The latest reliable information about Fe-Si-Al is given in the author’s work [34], where a fairly complete review of the compounds of this system was carried out based on data from works [35,36,37]. The author of [34] gives three types of triangulations of the Fe-Si-Al system with the presence of the FeAl₃Si₂ compound, which the author confirms by performing X-ray phase analysis. In fact, the author of [34] confirmed the presence of the FeAl₃Si₂ compound in the TCAL database of Fe₃Al₁₁Si₆, which in stoichiometry almost coincides with FeAl₃Si₂.

Thus, an analysis of the literature data shows that the Fe-Al-Si system contains stable ternary compounds, identified by microstructure and X-ray diffraction methods.

The value of ΔG°₂₉₈ for ternary compounds of the Fe-Al-Si system is not available in the literature; therefore, instead of the value of the standard Gibbs energy, the values of the standard enthalpy of formation of ternary compounds presented in

Table 5. Calculated values of the enthalpy of formation of ternary compounds of the Fe-Al-Si system [34].

№	Formula	Designation	Ratio, Mass%			ΔH°298, kJ/mol
			Fe	Al	Si
1	Fe5Al8Si7	F1	40.37	31.21	28.42	−480.93
2	FeAl3Si2	F2	28.94	41.95	29.11	−190.01
3	Fe3Al3Si2	F3	54.99	26.57	18.44	265.28
4	Fe4Al8Si3	F4	42.67	41.23	16.10	−459.46
5	Fe6Al15Si5	F5	38.07	45.98	15.95	−670.67
6	Fe4Al12Si3	F6	35.38	51.28	13.34	−580.78
7	FeAl4Si	F7	29.11	56.25	14.64	−141.40

[34] were used in the calculation.

When carrying out triangulation of the Fe-Al-Si subsystem from double state diagrams of Fe-Si, Al-Si, Fe-Al, and 7 ternary compounds Fe_xAl_ySi_z, twenty-five areas were formed: (1) Si-Fe₃Si₇-F₂; (2) Fe₃Si₇-FeSi₂-F₂; (3) FeSi₂-FeSi-F₂; (4) FeSi-F₁-F₂; (5) FeSi-F₄-F₁; (6) F₁-F₄-F₂; (7) FeSi-F₃-F₄; (8) FeSi-FeAl-F₃; (9) FeSi-Fe₅Si₃-FeAl; (10) Fe₅Si₃-Fe₃Si-FeAl; (11) Fe₃Si-Fe₃Al-FeAl; (12) Fe₃Si-Fe-Fe₃Al; (13) FeAl-F₆-F₃; (14) F₃-F₄-F₆; (15) F₄-F₅-F₂; (16) F₅-F₆-F₂; (17) F₆-F₇-F₂; (18) F₄-F₆-F₅; (19) FeAl-FeAl₂-F₆; (20) FeAl₂-Fe₂Al₅-F₆; (21) Fe₂Al₅-FeAl₃-F₆; (22) FeAl₃-Al-F₆; (23) Al-F₇-F₆; (24) Al-Si-F₇; (25) Si-F₂-F₇ (Figure 1).

Information about the conditions for the formation and stability of Si-Mn-Al ternary compounds is quite contradictory, and information about the structure obtained by various authors differs both in the number of phases and in the nature of phase equilibria between them [1]. In total, the work considers nine ternary compounds: Mn₄Al₃Si₂; Mn₃Al₃Si₂; Mn₃Al₃Si₄; Mn₃Al₈Si₉; Mn₄Al₉Si₃; Mn₃Al₉Si; Mn₃Al₁₂Si; Mn₂Al₉Si₂; and Mn₃Al₁₅Si₂. Of these, in [1], it is indicated that the Mn₄Al₃Si₂ compound can undergo polymorphic transformations leading to cracking of the metal after crystallization, but they do not indicate the recrystallization temperature or the possible mechanism of the formation of new compounds.

The value of ΔG°₂₉₈ for ternary compounds of the Si-Mn-Al system is not available in literature sources; therefore, the values of the enthalpies of formation were used for the calculation. The enthalpy of formation of ternary compounds in the Si-Mn-Al system was determined using the thermodynamic additivity method. The calculated values of the standard enthalpies of formation are given in

Table 6. Calculated values of the enthalpy of formation of ternary compounds of the Si-Mn-Al system [1].

№	Formula	Designation	Ratio, Mass%			ΔH°298, kJ/mol
			Mn	Al	Si
1	Mn4Al3Si2	M1	61.58	22.68	15.74	−274.52
2	Mn3Al3Si2	M2	54.59	26.81	18.60	−181.32
3	Mn3Al3Si4	M3	46.02	22.60	31.37	−351.68
4	Mn3Al8Si9	M4	26.02	34.08	39.90	−237.5
5	Mn4Al9Si3	M5	40.19	44.41	15.41	−376.5
6	Mn3Al9Si	M6	37.82	55.73	6.45	−289.42
7	Mn3Al12Si	M7	31.90	62.67	5.44	−297.82
8	Mn2Al9Si2	M8	26.87	59.39	13.74	−104.92
9	Mn3Al15Si2	M9	26.34	64.68	8.98	−214.92

.

When triangulating the Si-Mn-Al subsystem from double state diagrams Al-Si, Al-Mn, Mn-Si, and 9 ternary compounds Mn_xAl_xSi_x thirty-one areas were formed: (1) Mn-Mn₆Si-MnAl; (2) Mn₆Si-Mn₉Si₂-MnAl; (3) Mn₉Si₂-Mn₃Si-MnAl; (4) Mn₃Si-Mn₅Si₃-MnAl; (5) Mn₅Si₃-MnSi-MnAl; (6) MnSi-M₁-MnAl; (7) MnSi-M₃-M₁; (8) M₃-M₂-M₁; (9) MnSi-Mn₂Si₃-M₃; (10) Mn₂Si₃-Mn₁₁Si₁₉-M₃; (11) Mn₁₁Si₁₉-Si-M3; (12) Si-M₅-M₃; (13) Si-M₄-M₅; (14) Si-MnAl₄-M₇; (15) Si-M₈-M₇; (16) Si-M₉-M₈; (17) Si-Al-M₉; (18) M₈-M₉-M₇; (19) Al-M₉-M₇; (20) Al-M₇-MnAl₆; (21) MnAl₆-M₇-MnAl₄; (22) M₄-M₇-MnAl₄; (23) MnAl₄-M₄-M₅; (24) MnAl₄-M₅-M₆; (25) MnAl₄-M₆-MnAl₃; (26) MnAl₃-M₆-M₅; (27) MnAl₃-M₅-M₃; (28) MnAl₃-M₃-M₂; (29) MnAl₃-M₁-M₂; (30) MnAl₃-M₁-MnAl₁₁; (31) Mn₄Al₁₁-M₁-MnAl (Figure 2).

There is no information about the presence of Fe-Mn-Si ternary compounds. When triangulating the Fe-Mn-Si subsystem, thirteen areas were formed from the double phase diagrams of Fe-Mn, Fe-Si, and Mn-Si: (1) Fe-Mn-Mn₆Si; (2) Fe-Mn₆Si-Mn₉Si₂; (3) Fe-Mn₉Si₂-Fe₃Si; (4) Fe₃Si-Mn₉Si₂-Mn₃Si; (5) Fe₃Si-Mn₃Si-Mn₅Si₃; (6) Fe₃Si-Mn₅Si₃-MnSi; (7) Fe₃Si-MnSi-Fe₅Si₃; (8) Fe₅Si₃-MnSi-FeSi; (9) FeSi-MnSi-Mn₂Si₃; (10) FeSi-Mn₂Si₃-Mn₁₁Si₁₉; (11) FeSi- Mn₁₁Si₁₉-FeSi₂; (12) FeSi₂-Mn₁₁Si₁₉-Fe₃Si₇; (13) Fe₃Si₇-Mn₁₁Si₁₉-Si (Figure 3).

There is also no information about the presence of ternary compounds in the Al-Mn-Fe system. When triangulating the Al-Mn-Fe subsystem, eleven areas were formed from the double phase diagrams of Al-Mn, Fe-Mn, and Fe-Al: (1) Al-MnAl₆-FeAl₃; (2) MnAl₆-MnAl₄-FeAl₃; (3) MnAl₄-MnAl₃-FeAl₃; (4) MnAl₃-Fe₂Al₅-FeAl₃; (5) MnAl₃-FeAl₂-Fe₂Al₅; (6) MnAl₃-FeAl-FeAl₂; (7) MnAl₃-Fe₃Al-FeAl; (8) MnAl₃-Mn₄Al₁₁-Fe₃Al; (9) Mn₄Al₁₁-MnAl-Fe₃Al; (10) MnAl-Fe-Fe₃Al; (11) MnAl-Mn-Fe (Figure 4). Thus, the values of the enthalpy of formation in the Si-Mn-Al ternary system were calculated using the additive method. Binary systems (Fe-Si, Fe-Mn, Fe-Al, Mn-Si, Al-Si, Al-Mn) and ternary (Fe-Si-Al, Si-Mn-Al, Fe-Mn-Si, and Al) systems were considered.

Based on the tetrahedra of four particular three-component systems, Fe-Si-Al, Si-Mn-Al, Fe-Mn-Si, and Al-Mn-Fe, a diagram of the phase composition of the four-component system Fe-Si-Mn-Al was constructed (Figure 5).

Table 7. Quadruple system Fe-Si-Mn-Al.

Fe-Si-Al	Si-Mn-Al	Fe-Mn-Si	Al-Mn-Fe
Si-Fe3Si7-F2	Mn-Mn6Si-MnAl	Fe-Mn-Mn6Si	Al-MnAl6-FeAl3
Fe3Si7-FeSi2-F2	Mn6Si-Mn9Si2-MnAl	Fe-Mn6Si-Mn9Si2	MnAl6-MnAl4-FeAl3
FeSi2-FeSi-F2	Mn9Si2-Mn3Si-MnAl	Fe-Mn9Si2-Fe3Si	MnAl4-MnAl3-FeAl3
FeSi-F1-F2	Mn3Si-Mn5Si3-MnAl	Fe3Si-Mn9Si2-Mn3Si	MnAl3-Fe2Al5-FeAl3
FeSi-F4-F1	Mn5Si3-MnSi-MnAl	Fe3Si-Mn3Si-Mn5Si3	MnAl3-FeAl2-Fe2Al5
F1-F4-F2	MnSi-M1-MnAl	Fe3Si-Mn5Si3-MnSi	MnAl3-FeAl-FeAl2
FeSi-F3-F4	MnSi-M3-M1	Fe3Si-MnSi-Fe5Si3	MnAl3-Fe3Al-FeAl
FeSi-FeAl-F3	M3-M2-M1	Fe5Si3-MnSi-FeSi	MnAl3-Mn4Al11-Fe3Al
FeSi-Fe5Si3-FeAl	MnSi-Mn2Si3-M3	FeSi-MnSi-Mn2Si3	Mn4Al11-MnAl-Fe3Al
Fe5Si3-Fe3Si-FeAl	Mn2Si3-Mn11Si19-M3	FeSi-Mn2Si3-Mn11Si19	MnAl-Fe-Fe3Al
Fe3Si-Fe3Al-FeAl	Mn11Si19-Si-M3	FeSi- Mn11Si19-FeSi2	MnAl-Mn-Fe
Fe3Si-Fe-Fe3Al	Si-M5-M3	FeSi2-Mn11Si19-Fe3Si7
FeAl-F6-F3	Si-M4-M5	Fe3Si7-Mn11Si19-Si
F3-F4-F6	Si-MnAl4-M7
F4-F5-F2	Si-M8-M7
F5-F6-F2	Si-M9-M8
F6-F7-F2	Si-Al-M9
F4-F6-F5	M8-M9-M7
FeAl-FeAl2-F6	Al-M9-M7
FeAl2-Fe2Al5-F6	Al-M7-MnAl6
Fe2Al5-FeAl3-F6	MnAl6-M7-MnAl4
FeAl3-Al-F6	M4-M7-MnAl4
Al-F7-F6	MnAl4-M4-M5
Al-Si-F7	MnAl4-M5-M6;
Si-F2-F7	MnAl4-M6-MnAl3
	MnAl3-M6-M5
	MnAl3-M5-M3
	MnAl3-M3-M2
	MnAl3-M1-M2
	MnAl3-M1-MnAl11
	Mn4Al11-M1-MnAl

presents a list of all elementary triangles of the studied systems.

As a result of calculations, elementary tetrahedra that make up this system were obtained. There are two methods for constructing a phase composition diagram. The first method is geometric, very complex for a given tetrahedron due to the large number of phases formed. As can be seen from Table 7, it consists of 80 stable phase triangles. It is extremely difficult to draw all the connections correctly and not miss or see the intersection of the boundaries of the triangles. Therefore, one of the methods of closing a triangle onto a tetrahedron was used.

This method consists of searching for triangles that have two identical phases “if two triangles from the nearest triple partial system have two identical phases, then they form a tetrahedron, etc.” According to Table 7, we first consider the first two columns, find triangles that have two identical phases, and write them down. Next, we consider the phase compositions of the second and third columns. We also repeat finding two identical phases, etc. Following this method, fifty-six tetrahedra were obtained.

The breakdown of the general system was carried out for the most part taking into account congruent connections. The sum of the relative volumes of elementary tetrahedra is equal to unity (1.0).

Table 8. List of elementary tetrahedra in the Fe-Si-Mn-Al system and their volumes relative to the volume of the original quaternary system, equal to 1 in arbitrary units.

№	Tetrahedrons	Volume	№	Tetrahedrons	Volume
1	Si-Fe3Si7-F2-Mn11Si19	0.116356	29	Fe3Si-Mn3Si-MnAl-Mn5Si	0.025065
2	FeSi2-Fe3Si7-F2-Mn11Si19	0.008677	30	Fe3Si-Mn3Si-MnAl-MnSi	0.059887
3	FeSi2-FeSi-F2-Mn11Si19	0.036933	31	Fe3Si-M1-MnAl-MnSi	0.014704
4	F1-FeSi-F2-M3	0.003658	32	Fe3Si-M1-M3-MnSi	0.030352
5	F1-FeSi-F4-M3	0.015307	33	M3-M2-M1-Fe3Si	0.005535
6	F1-F2-F4-M3	0.006422	34	MnSi-Mn2Si3-M3-FeSi	0.014428
7	FeSi-F3-F4-MnAl3	0.006435	35	Mn11Si19-Mn2Si3-M3-FeSi	0.00526
8	FeSi-F3-FeAl-MnAl3	0.016113	36	Mn11Si19-Si-M3-F7	0.034922
9	FeSi-Fe5Si3-FeAl-MnSi	0.049261	37	M5-Si-M3-F7	0.032996
10	Fe3Si-Fe5Si3-FeAl-MnSi	0.095044	38	M5-Si-M4-F7	0.006298
11	Fe3Si-Fe3Al-FeAl-MnAl4	0.009075	39	Si-M4-M7-F7	0.015784
12	Fe3Si-Fe3Al-Fe-MnAl	0.013431	40	Si-M8-M7-F7	0.006059
13	FeAl-F6-F3-MnAl3	0.017125	41	Si-M8-M9-F7	0.005186
14	F4-F6-F3-MnAl3	0.000713	42	M7-M8-M9-F7	0.000829
15	F4-F5-F2-M3	0.002896	43	Al-M8-M9-F7	0.00344
16	F6-F5-F2-M3	0.002709	44	Al-M-MnAl6-F7	0.003976
17	F6-F7-F2-M3	0.004219	45	MnAl6-M7-MnAl4-FeAl3	0.001851
18	F4-F6-F5-M3	0.000572	46	M4-M7-MnAl4-F7	0.00088
19	FeAl-F6-FeAl2-MnAl3	0.008866	47	M4-M5-MnAl4-F7	0.010998
20	Fe2Al5-F6-FeAl2-MnAl3	0.003009	48	M6-M5-MnAl4-F7	0.000627
21	Fe2Al5-F6-FeAl3-MnAl3	0.002418	49	M6-MnAl3-MnAl4-FeAl3	0.00175
22	Al-F6-FeAl3-MnAl6	0.013729	50	M6-MnAl3-M5-F7	0.001128
23	F7-F6-MnAl6-Al	0.003284	51	M3-MnAl3-M5-F3	0.005089
24	F7-Si-M9-Al	0.084923	52	M3-MnAl3-M2-Fe3Si	0.029251
25	F7-Si-M3-F2	0.018758	53	M1-MnAl3-M2-Fe3Si	0.01467
26	Fe-Mn6Si-MnAl-Mn	0.025991	54	M1-MnAl3-Mn4Al11-Fe3Al	0.002839
27	Fe-Mn6Si-MnAl-Mn9Si	0.007567	55	M1-MnAl-Mn4Al11-Fe3Al	0.033254
28	Fe3Si-Mn3Si-MnAl-Mn9Si	0.012391	56	Fe-MnAl-Fe3Si-Mn9Si2	0.04706
Total					1.0000

presents a list of elementary tetrahedra in the Fe-Si-Al-Mn system and their volumes relative to the volume of the original quaternary system, equal to 1 in arbitrary units.

The results of the calculations (Table 8) confirm the reliability of the breakdown of the phase structure diagram of the Fe-Si-Mn-Al system. Figure 6 shows the tetrahedron of the Fe-Si-Al-Mn quaternary system.

Based on the results of TDA and the constructed diagram of the real phase relationships in the Fe-Si-Mn-Al system, two regions of crystallization of leboite (Fe₃Si₇) were determined—the secondary and primary regions.

The secondary crystallization area of leboite belongs to the tetrahedron—Si-Fe₃Si₇-Mn₁₁Si₁₉-FeAl₃Si₂ (Figure 6). Alloys having compositions in this area must be stable. Silicon atoms are primarily crystallized (t_mp = 1410 °C). Crystallization of leboite (t_mp = 1205 °C) occurs inside an already formed matrix of silicon crystals. Next, Mn₁₁Si₁₉ crystals begin to fall out (t_mp = 1155 °C). Recrystallization of leboite according to the scheme Fe₃Si₇ → 3FeSi₂ + Si and an increase in volume by 17% occurs at 940 °C. At this temperature, the FeAl₃Si₂ compound (t_mp ˂ 850 °C) is in a liquid state. The presence of a carcass of silicon crystals and still liquid FeAl₃Si₂ reduces the effect of internal stress, and the increase in volume does not have a significant effect. Therefore, with sufficiently rapid cooling, as is common in metallurgical practice, compositional alloys belonging to the Si-Fe₃Si₇-Mn₁₁Si₁₉-FeAl₃Si₂ area are not subject to destruction and further disintegration.

The primary crystallization region is characteristic of the region bounded by the FeSi₂-Fe₃Si₇-Mn₁₁Si₁₉-FeAl₃Si₂ tetrahedron (marked in blue), having a volume of 0.036933 ~ 3.7% (Figure 6). Compositional alloys belonging to this area are unstable and tend to fracture. This range of compositions is characterized by primary crystallization of leboite (t_mp = 1205 °C). Next, Mn₁₁Si₁₉ (t_mp = 1155 °C) crystals begin to fall out. Meaning that the carcass of the alloy ingot is formed from Fe₃Si₇-Mn₁₁Si₁₉ crystals. Recrystallization of leboite at 940 °C leads to an increase in internal stress due to an increase in volume, which leads to direct destruction of the ingot carcass and the formation of numerous cracks. The formation of cracks in the ingot is the initial effect of destruction. Subsequently, atmospheric moisture interacts with excess phosphorus and calcium-containing phases with the release of gaseous products, which leads to complete disintegration of the alloy ingots.

Consequently, when planning and developing technology for the melting process of complex alloys based on Fe-Si-Mn-Al, it is necessary to regulate the initial compositions of the charge and the resulting alloy so as not to fall into the region of primary crystallization of leboite (Fe₃Si₇). The report [17] indicates that the ternary compound Mn₄Al₃Si₂ (M1) has a tendency to undergo polymorphic transformations during crystallization. However, this compound is not in the range of compositions of industrial alloys and was not considered by us.

Experiment

(1)

Melting process of complex alloy Fe-Si-Mn-Al

The melting process was carried out in a continuous manner, with periodic release of the alloy every two hours into cast iron molds. The process is slag-free. The charge was uniformly heated by the exhaust reaction gases, which created favorable conditions for the development of reduction processes. The reaction zone was characterized by high temperature, and the metal came out actively. Upon completion of the release of the melt, gases were rapidly released from the tap hole, which indicated the complete release of the metal from the reaction zone, after which fresh charge was loaded into the furnace to form a cone around the electrode [38,39,40,41,42,43].

The process of melting a complex alloy: the release of the alloy and the formation of a cone from the charge around the electrode of the ore-thermal furnace are presented in Figure 7.

Based on thermodynamic diagram analysis (TDA), we set the expected composition of the charge to obtain a complex AMS alloy with a content of 10–15% Fe; 40–50% Si; 30–40% Mn; 5–12% Al. The preliminary calculation was carried out by the iteration method, which is based on a numerical approximate method for solving technological problems using Microsoft Excel spreadsheets, and the charge was weighed: high-ash coal from the «Saryadyr» deposit—20 kg; manganese ore from the «Bogach» deposit—8 kg, quartzite—2.53 kg. Quartzite was used in the charge mixture to adjust the chemical composition and neutralize residual carbon [44].

The resulting alloy of each release was weighed, and then samples were taken for chemical analysis. Chemical analysis of samples (

Table 9. Chemical composition of complex AMS alloys of experimental melts.

№ of Heats	Fe	Si	Al	Mn	Ca	C	S	P
4	12.3	44.1	2.5	31.3	5.7	0.5	0.01	0.06
5	10.8	45.4	3.4	32.2	5.3	-	-	-
6	11.3	46.1	2.9	33.8	4.26	-	-	-
7	11.7	45	3.8	32.1	6.2	0.5	0.013	0.09
8	11.1	44.9	2.2	36.4	4.7	-	-	-
9	10.82	41.75	2.5	40.96	3.2	-	-	-
10	9.8	46.7	3.3	32.8	3.6	0.5	0.015	0.08
11	8.1	46.8	5.8	32.6	4.8	-	-	-
12	10.2	47.8	8	31.1	2.8	-	-	-
13	10.1	47.5	7.9	30.2	3.2	0.3	0.02	0.07
14	9.2	47.3	9.7	30.2	2.26	-	-	-
15	10.2	44.3	8.3	32.6	3.8	-	-	-
16	10.3	43.9	9.2	35.1	0.9	0.5	0.013	0.08
17	14.13	40.14	3.2	38.62	3.2	-	-	-
18	10.2	43.5	5.7	34.7	5.5	-	-	-
Σav.	10.68	45.01	5.23	33.65	4.26	0.45	0.013	0.073

) was carried out in accordance with GOST-22772.4-77, GOST-22772.6-77, GOST-22772.7-96.

The maximum manganese content in this charge mixture is 40.96% in heat № 9. The minimum manganese content is 30.2% in samples of № 13 and № 14. The unweighted average manganese content in the alloy is 33.65%. Silicon in the alloy varies from 40.14 to 47.8%; the weighted average content is 45.01%. The weighted average content of aluminum in the alloy is 5.23%.

The practical application of the results of thermodynamic analysis to the melting process of the AMS complex alloy comes down to finding elementary tetrahedra within which their compositions are limited. To determine the manufacturability of the resulting alloys during the melting process, their chemical compositions were recalculated to the main elements of the Fe-Si-Mn-Al complex alloy, which are given in

Table 10. Chemical composition of the complex master alloy of experimental melts.

№ of Heats	Fe	Si	Al	Mn	Tetrahedron	Volume
4	13.64	48.89	2.77	34.70	Si-Fe3Si7-F2-Mn11Si9	0.116356
5	11.76	49.46	3.70	35.08
6	12.01	48.99	3.08	35.92
7	12.63	48.60	4.10	34.67
8	11.73	47.46	2.33	38.48	FeSi2-Fe3Si7-F2-Mn11Si9	0.008677
9	11.27	43.48	2.60	42.65
10	10.58	50.43	3.56	35.42	Si-Fe3Si7-F2-Mn11Si9	0.116356
11	8.68	50.16	6.22	34.94
12	10.50	49.23	8.24	32.03
13	10.55	49.63	8.25	31.56
14	9.54	49.07	10.06	31.33
15	10.69	46.44	8.70	34.17
16	10.46	44.57	9.34	35.63
17	14.70	41.77	3.33	40.19	Mn11Si9-Mn2Si3-M3-FeSi	0.00526
18	10.84	46.23	6.06	36.88	Si-Fe3Si7-F2-Mn11Si9	0.116356

.

The resulting prototypes of heats № 4–7 and № 10–18 of the AMS alloy after cooling and storage were stable and did not collapse. Experimental samples of the alloy melts № 8 and № 9 were destroyed and subsequently crumbled into fine powder.

(2)

X-ray phase evaluation of the Fe-Si-Mn-Al complex alloy

The object of the study were representative samples № 7, 9, and 14 of the experimental alloy, the structure of which was formed during natural cooling (Table 10). Phase analysis was carried out by comparing the experimental and theoretical (estimated and table) values of the intensity of X-ray lines. The coincidence of the experimental and table values of d/n interplanar distances and the relative intensity of interference lines made it possible to unambiguously identify the phases present in the samples (Figure 8, Figure 9 and Figure 10).

The most pronounced phases are pure silicon (structurally free silicon) and phases containing aluminum, silicon, manganese, and iron in ratios corresponding to the formulas: FeAl₃Si₂, Fe₃Si₇, Mn₁₁Si₉, and FeSi₂ (aluminosilicides and silicides of manganese and iron).

In alloy samples of compositions № 7 (Figure 8) and № 14 (Figure 10), iron aluminosilicide—FeAl₃Si₂, manganese silicide—Mn₁₁Si₉, leboite—Fe₃Si_7, and structurally free silicon were found, which is explained by the high silicon content in the alloy.

In the alloy sample of composition № 9 (Figure 9), the following phases were identified: leboite (Fe₃Si₇), which extends towards iron silicide FeSi₂, iron aluminosilicide—FeAl₃Si_2, and manganese silicide—Mn₁₁Si₉. As we described above, samples of sample № 9 crumbled, so we assume that this is affected by leboite—Fe₃Si₇, which after crystallization passes into FeSi₂, and in other samples (№ 7 and № 14), pure silicon affects and does not allow crumbling. The X-ray phase analysis method allowed us to identify the main crystalline phases in the alloy under study, their effect on the physical and mechanical properties of the material, and confirm the correctness of the thermodynamic diagram analysis of the obtained data.

4. Discussion

The thermodynamic-diagram analysis of Fe-Si-Mn-Al made it possible to identify the compositional region of the primary crystallization of leboite (Fe₃Si₇), which is presumably the main cause of destruction of the AMS alloy.

In relation to the Fe-Si-Mn-Al system under consideration, six binary systems were analyzed: Fe-Si, Fe-Mn, Fe-Al, Mn-Si, Al-Si, Al-Mn, and four ternary systems: Fe-Si-Al, Si-Mn-Al, Fe-Mn-Si, and Al-Mn-Si. Based on the results of thermodynamic diagram analysis, 80 possible ternary phases were identified.

For the first time, a breakdown of the Fe-Si-Mn-Al system diagram for the solid state involving complex chemical compounds has been carried out: Fe₅Al₈Si₇; FeAl₃Si₂; Fe₃Al₃Si₂; Fe₄Al₈Si₃; Fe₆Al₁₅Si₅; Fe₄Al₁₂Si₃; FeAl₄Si; Mn₄Al₃Si₂; Mn₃Al₃Si₂; Mn₃Al₃Si₄; Mn₃Al₈Si₉; Mn₄Al₉Si₃; Mn₃Al₉Si; Mn₃Al₁₂Si; Mn₂Al₉Si₂; Mn₃Al₁₅Si₂. It was determined that the Fe-Si-Mn-Al system consists of 15 stable tetrahedra.

It has been established that compositional alloys belonging to the region of primary crystallization of leboite (Fe₃Si₇), namely the tetrahedron FeSi₂-Fe₃Si₇-Mn₁₁Si₁₉-FeAl₃Si₂, are prone to initial destruction and subsequent disintegration. A possible mechanism for the destruction of alloy ingots during crystallization, which occurs due to an increase in volume and internal stresses of the carcass of leboite crystals, is shown.

The results of theoretical studies are confirmed by the practical melting process of the AMS alloy in an electric furnace with a transformer power of 200 kVA. The bulk of the melted AMS alloy in composition belongs to the region of the Si-Fe₃Si₇-F₂-Mn₁₁Si₉ tetrahedron (V = 0.116 m³), which is the most voluminous in the Fe-Si-Mn-Al system. The resulting alloy samples were stable and did not collapse.

Experimental samples of the alloy (heats № 8–9) collapsed after crystallization and cooling. In composition, they belong to the region of the FeSi₂-Fe₃Si₇-F₂-Mn₁₁Si₉ tetrahedron, which confirms the possible mechanism of destruction of the AMS alloy that we accepted.

The results obtained in this work are consistent with the conclusions made in the studies of the authors [45,46]. In the work [45] also noted a significant influence of phase transformations on the structural characteristics of alloys, especially on the tendency to destruction in the presence of critical phase components. In his work, special attention is paid to the mechanisms of crystallization and the influence of chemical composition (Al, P) on the stability of alloys, which confirms the conclusions made in this study.

Another author [34], who was engaged in obtaining a complex alloy FSA (ferrosilicon aluminum) from high-ash coal, in his studies detailed the effect of ternary and quaternary phases on the physicochemical properties of alloys, emphasizing the importance of thermodynamic analysis for predicting phase stability and preventing destruction. His approach to using the thermodynamic additivity method to calculate the standard enthalpies of phase compounds also found application in our study, which allowed us to conduct a deep analysis of the Fe-Si-Mn-Al system and make reasonable conclusions about the tendency of alloys to self-destruction.

In addition to Kazakhstan in the post-Soviet republics, the development and research of complex silicon, manganese, and aluminum containing alloys from man-made and secondary resources (manganese-containing dust, slag, sludge of wet slag separation, sludge of electrolytic manganese dioxide production, slag from steel rolling shops, alum-containing slag of secondary aluminum production, waste from the processing of high-ash hard coal from the Tkibuli deposit, etc.) is carried out by the Institute of Metallurgy and Materials Science named after A.A. Kuznetsov. The Institute of Metallurgy and Materials Science, named after Ferdinand Tavadze, deals with the mining and metallurgical industries. Ferdinand Tavadze Institute of Metallurgy and Materials Science (Georgia) [46].

The results of experimental smelting show that electrocarbothermal processing of the above mentioned technogenic and secondary metal-containing resources of the mining and metallurgical industry of Georgia satisfies the requirements of the technology of complex alloy smelting. In the received samples of complex alloy contains, mass %: silicon 26–32; aluminium 17–25; manganese 28–50; iron 6–14; carbon 0.6–1.3; phosphorus 0.02–0.09. Presumably this alloy contains the following phases: Mn₁₁Si₁₉-Si-Mn₃Al₃Si₄-FeAl₄Si or Mn₄Al₉Si-Si-Mn₃Al₃Si₄-FeAl₄Si.

Studies and analysis of melting of aluminosilicomanganese from technogenic and secondary mining and metallurgical resources of Georgia showed that the waste of mining and metallurgical industry can be used for smelting of aluminosilicomanganese alloy. Also one of the directions of application of complex alloys containing silicon, manganese, and aluminum is the use as a reducing agent in the smelting of refining ferromanganese, where the complex alloy was able to exclude from the composition of the charge traditionally used silicomanganese. Evaluation of technical and economic indicators also characterizes the same from the positive side [46].

Thus, the theoretical studies carried out using the TDA method for the quaternary system Fe-Si-Mn-Al and experimental tests on the melting process of the AMS alloy made it possible to determine the critical region of the compositions of the AMS alloy, which have a tendency to self-destruct with their further disintegration. The results of the research will allow manufacturers to show interest in introducing and mastering the technology of melting process AMS alloy using manganese ores and high-ash coals and guarantee the production of alloy compositions that are resistant to destruction.

5. Conclusions

The conducted study of the Fe-Si-Mn-Al system demonstrated a significant effect of phase compounds on the structural and physicochemical properties of alloys, in particular on their tendency to crumble. It was found that one of the key causes of alloy destruction is the formation and recrystallization of the leboite phase (Fe₃Si₇), which leads to an increase in volume and the creation of internal stresses that cause cracks in the alloy structure.

It was experimentally confirmed that alloys whose composition falls within the region of primary leboite crystallization are prone to self-destruction and crumble. In contrast, alloys formed in the region of secondary leboite crystallization demonstrate significantly higher stability, which is due to the presence of a structural matrix that prevents the propagation of internal stresses.

The results of thermodynamic diagram analysis and experimental data from X-ray phase analysis showed that in order to obtain stable alloys, it is necessary to carefully control the composition of the charge in order to avoid falling into the critical regions of primary leboite crystallization. This is especially important when developing the technology for melting complex alloys based on Fe-Si-Mn-Al using substandard manganese-containing ores and high-ash coals.

Based on the data obtained, it can be concluded that the proposed methodology for analyzing phase compositions and optimizing the chemical composition of the charge can significantly increase the stability of the resulting alloys, which opens up new opportunities for their industrial application. Thus, the studies conducted provide a reliable basis for further improvement of alloy production technologies and their widespread implementation in the metallurgical industry, which contributes to increasing the efficiency and reliability of production processes.