ALUMINUM-BASED ALLOY

Abstract

The invention relates to the field of aluminum-based metallurgy and can be used for manufacturing products that operate in corrosive environments under high loads, particularly at elevated and cryogenic temperatures. The claim is for a new aluminum alloy with a structure consisting of an aluminum solution, precipitates, and a eutectic phase formed by elements such as magnesium, manganese, iron, chromium, zirconium, titanium, and vanadium. Furthermore, the alloy additionally contains silica and scandium, where at least 75% of each element in the zirconium and scandium group forms precipitates with an L12-type lattice in an amount of at least 0.18% by volume and a particle size of no more than 20 nm, with the specified alloying element distribution.

Description

ALUMINUM-BASED ALLOY Technical field of the invention The invention relates to the field of aluminum-based metallurgy and can be used in the manufacture of products (including welded structures) that operate in corrosive environments (humid atmospheres, brackish water, salt water, and other corrosive environments) under high loads, particularly at elevated and cryogenic temperatures. The material can be produced in the form of rolled products, such as rolled plates and sheets, drawn sections and tubes, forgings, and other semi-finished forged products, as well as in the form of powders, flakes, granules, etc. The proposed alloy is primarily intended for use in vehicles such as boat hulls and other watercraft, hull parts, plates and other tank components of aircraft, trucks and railways, particularly for the transport of chemically active substances, as well as for use in the food industry, etc. Previous technology Due to their high corrosion resistance, weldability, high elongation values, and ability to operate at cryogenic temperatures, forged Al-Mg system alloys (5xxx series) have been widely used for products operating in corrosive environments, in particular, they are intended for use in river and sea waters (transport, water pipelines, etc.), tanks for transporting liquefied gas and chemically active liquids. The main disadvantage of the 5xxx series alloys is the low level of strength properties of the tempered semi-finished forged products; for example, the elongation strength of 5083 type alloys after tempering generally does not exceed 150 MPa (see Industrial aluminum alloys: Reference book. SG Aliev, MB Altman, SM Ambartsumyan et al. Moscow: Metallurgy, 1984). One way to improve the strength properties of hardened 5xxx series alloys is through further alloying with transition metals, among which Zr and, to a lesser extent, Hf, V, Er, and a few other elements have achieved the most widespread use. The main distinguishing feature of these alloys, in this case, compared to other Al-Mg system alloys (of the 5083 type), is the content of dispersion-forming elements, particularly those with the LI2 lattice. In this case, the combined effect of increased strength properties is achieved through the hardening of the aluminum solid solution, primarily with magnesium, and the presence in the structure of various secondary precipitate phases formed during homogenization quenching (heterogenization). Thus, an alloy claimed by Alcoa (patent RU 2431692) is known. The material contains (% by weight): magnesium 5.1-6.5, manganese 0.4-1.2, zinc 0.45-1.5, zirconium up to 0.2, chromium up to 0.3, titanium up to 0.2, iron up to 0.5, silicon up to 0.4, copper 0.002-0.25, calcium up to 0.01, beryllium up to 0.01, at least one element from the group: boron, carbon, each up to 0.06, at least one element from the group: bismuth, lead, tin, each up to 0.1, scandium, silver, lithium, each up to 0.5, vanadium, zinc, yttrium each up to 0.25, at least one element from the group: nickel and cobalt, each up to 0.25, the remainder being aluminum and unavoidable impurities, with the total magnesium and zinc content of 5.7-7.3% by weight and the total iron, cobalt and / or nickel content of no more than 0.7% by weight, the remainder is aluminum and unavoidable impurities.Among the disadvantages of this alloy, its relatively low overall strength properties should be noted, which sometimes limits its use. The presence of many small additives reduces the production rate, adversely affecting the performance of foundry facilities, and the high magnesium content leads to reduced processability and corrosion resistance. A significantly greater increase in strength properties than that of 5083-type alloys is achieved with the combined content of scandium and zirconium additives. In this case, the effect is achieved through the formation of a much larger quantity of precipitates (typically 2–20 nm in size), which are resistant to high-temperature heating during the deformation and subsequent tempering of semi-finished welded products, thus providing a higher level of strength properties. For example, a material based on the Al-Mg system, alloyed together with zirconium and scandium additives, is known; in particular, CRISM “Prometey” claimed the material, disclosed in patent RU 2268319, which is known as alloy 1575-1. The alloy is characterized by a higher level of strength properties than alloys of type 5083 and 1565. The claimed material contains (% by weight) magnesium 5.5-6.5%, scandium 0.10-0.20%, manganese 0.5-1.0%, chromium 0.10-0.25%, zirconium 0.05-0.20%, titanium 0.02-0.15%, zinc 0.1-1.0%, boron 0.003-0.015%, beryllium 0.0002-0.005%, and the remainder is aluminum. Among the disadvantages of the material, one should note the high magnesium content, which sometimes adversely affects the processing capacity during the deformation process, and the presence of the β-AlsMgs phase in the final structure, which in some cases leads to a decrease in corrosion resistance. A material claimed in Kaiser Aluminium patent ES 6139653 is also known. An alloy based on the Al-Mg-Sc system is claimed, containing additional elements selected from the group including Hf, Mn, Zr, Cu, and Zn, in particular (wt%) 1.0-8.0% Mg, 0.05-0.6% Se, as well as 0.05-0.20% Hf and / or 0.05-0.20% Zr, 0.5-2.0% Cu, and / or 0.5-2.0% Zn. In a particular version, the material may additionally contain 0.10.8 wt% Mn. Among the disadvantages of the claimed material are the relatively low strength properties with magnesium content at the lower limit, as well as the low corrosion resistance and low processability during deformation with magnesium content at the upper limit. At the same time, to ensure a high level of properties, it is necessary to regulate the proportion of particle sizes formed by elements such as Se, Hf, Mn, and Zr. A material claimed by the Aluminum Company of America and described in patent USD 5,624,632 is known. The aluminum-based alloy contains (by weight) magnesium 3–7%, zirconium 0.05–0.2%, manganese 0.2–1.2%, silica up to 0.15%, and approximately 0.05–0.5% of precipitate-forming elements selected from the group: Se, Er, Y, Cd, Ho, Hf; the remainder is aluminum and extraneous elements and impurities. Among the disadvantages, the relatively low strength properties should be noted when using alloying elements within the lower range. A RUSAL material is known, described in patent ru2683399cl. The aluminum-based alloy contains (% by weight) zirconium 0.10–0.50%, iron 0.10–0.30%, manganese 0.5%, chromium 0.15–0.6%, scandium 0.09–0.25%, titanium 0.02–0.10%, at least one element selected from the group: silicon 0.10–0.50%, cerium 0.10–5.0%, calcium 0.10–2.0%, and optionally magnesium 2.0–5.2%. A material, claimed by NanoAl and described in application WO2018165012, is known. The alloy contains aluminum, magnesium, manganese, silica, zirconium, and ALZr L12 nanoparticles with an average size of approximately 20 nm, in quantities of 20211 / m3 or more. The particles also contain one or more elements from the tin, strontium, and zinc groups. The aluminum alloy, under work-hardened conditions, has a yield strength of at least 190 MPa, a tensile strength of at least 320 MPa, and an elongation of at least 18%. Among the disadvantages of the alloy is its low strength under quenched conditions. The prototype is the known technical solution of the invention under patent US651004 of Eads Deutschland GmbH. In particular, the corrosion-resistant weldable material with the triple phase Al, Zr, Se, containing mainly (% by weight) magnesium 5-6%, zirconium 0.05-0.15%, manganese 0.05-0.12%, titanium 0.01-0.2%, a total of 0.05-0.5% of scandium and terbium and optionally at least one additional element selected from the group consisting of various lanthanides, wherein scandium and terbium are present as mandatory elements, and at least one element selected from the group including copper 0.1-0.2% and zinc 0.1-0.4%; the remainder being aluminum and unavoidable impurities of not more than 0.1% silica. Among the disadvantages of this material are the presence of rare and expensive elements. Furthermore, this material may not be sufficiently resistant to high temperatures during the heating process. Disclosure of the invention The objective of the invention is the creation of a new high-strength aluminum alloy, characterized by low cost and a set of high-level physical and mechanical properties, processability and corrosion resistance, in particular, having a high level of mechanical properties after tempering (minimum temporary strength 350 MPa, minimum yield strength 250 MPa and minimum elongation 5%) and high processability during hot and cold deformation. The technical result is the solution to the objective and ensuring high processing capacity during the deformation process while increasing the mechanical properties of the alloy due to the precipitation of the Zr-containing phase with the LI2 type crystal lattice. The achievement of this objective and the specified technical result are guaranteed by the fact that an alloy is claimed with a structure consisting of an aluminum solution, precipitates, and a eutectic liquid phase formed by elements such as magnesium, manganese, iron, chromium, zirconium, titanium, and vanadium. Furthermore, the alloy additionally contains silica and scandium; at least 75% of each element in the zirconium and scandium group forms precipitates with an LI2-type lattice in quantities of at least 0.18% by volume and with a particle size of no more than 20 nm, with the following alloying element distribution (% by weight): zzcnnn / zznz / e / YiAi Magnesium 4.0-5.5 Manganese 0.3-1.0 Iron 0.08-0.25 Chromium 0.08-0.18 Zirconium 0.06-0.16 Titanium 0.02-0.15 Vanadium 0.02-0.06 Scandium 0.01-0.28 Silica 0.06-0.18 Aluminum and unavoidable impurities Remainder Summary of the invention Unexpectedly, it has been found that the increased strength properties are achieved through the combined positive effect of solid solution hardening of the aluminum solution due to magnesium and secondary phases containing manganese, chromium, zirconium, scandium, and vanadium, all of which are resistant to high-temperature heating. Simultaneously, further alloying with silica and vanadium decreases the solubility of zirconium and scandium in the aluminum solution, increasing the volume fraction of precipitation particles up to 20 nm in size and improving hardening efficiency. In this case, the aluminum alloy structure must contain the minimally alloyed aluminum solution and precipitation particles, in particular AΙβMη phases with a size of up to 200 nm, AECr with a size of up to 50 nm and particles of type AEZr and / or ALfZr, Se) and / or AL / Zr, V) with the LI2 type lattice with a size of up to 20 nm. The justification for the claimed quantities of the alloy components that ensure the achievement of the given structure in this alloy is provided below. Magnesium is required at a concentration of 4.0–5.5% by weight to enhance the overall mechanical properties through solid solution hardening. If the magnesium content exceeds the stated amount, this element will reduce workability during metallurgy, for example, when rolling ingots, significantly impacting the yield ratio during deformation. Contents below 4% by weight will not provide the minimum required strength properties. A quantity of 0.06-0.16% by weight of zirconium is required to ensure the hardening of the dispersion with the formation of precipitations of ALZr EL or Ah(Zr, Se) and / or AL / Zr, V) phases in the presence of the relevant elements. Amounts of 0.01-0.28% by weight and 0.01-0.06% by weight, respectively, of scandium and vanadium are required to ensure the required level of strength properties due to dispersion hardening with the formation of metastable phase precipitates additionally containing zirconium with L12 crystal lattice. In general, zirconium, scandium, and vanadium are redistributed between the aluminum matrix and the ALZr metastable phase precipitates with the LI2-type lattice, and the number of particles is determined by the solubility of these elements at the decomposition temperature. zzcnnn / zznz / e / YiAi If the zirconium concentration in the alloy is greater than 0.16% by weight, high melting temperatures are required, which in some cases is not technically feasible under semi-continuous ingot casting conditions. By employing standard smelting conditions with zirconium content of more than 0.16% by weight, it is possible to form the DO23 type lattice phase in the primary crystal structure, which is unacceptable. The zirconium, scandium, and vanadium content below the declared level will not provide the minimum required level of strength properties due to an insufficient amount of secondary phase precipitation with the El 2 type lattice. A chromium content of 0.08–0.18% by weight is required to increase the overall level of mechanical properties due to dispersion hardening with the formation of the AECr secondary phase. If the chromium content is higher than the declared content, this element will reduce workability during metallurgy, for example, when rolling ingots, which will significantly negatively affect the yield ratio during deformation. A content below 0.1% by weight will not provide the minimum required level of strength properties. A manganese content of 0.4–1.0% by weight is necessary to increase the overall level of mechanical properties due to dispersion hardening with the formation of the AE₂Mn secondary phase. If the manganese content is higher than the stated amount, this element will reduce workability during metallurgy, for example, when rolling ingots, due to the possible formation of primary crystals, which significantly negatively impacts the yield ratio during deformation. A content below 0.3% by weight will not provide the minimum required level of strength properties. When the content exceeds 1.0% by weight, primary crystals of the AE₂Mn phase will form, reducing workability during deformation. Silica is required to reduce the solubility of zirconium, scandium, and vanadium in the aluminum solution. As a result, the main effect of these elements is associated with an increase in the supersaturation of zirconium, scandium, and vanadium in the aluminum solution during profile casting. This ensures the release of more secondary-phase dispersoids with the LI2 lattice during subsequent homogenization quenching and enhances the dispersion hardening effect. Furthermore, it has been experimentally established that, in the presence of silica, less than 75% of the zirconium and scandium content of the alloy, within the claimed concentration range of alloying elements, forms LI2-type lattice precipitates in quantities of at least 0.18% by volume. With a silica content of 0.At 0.8% zzcnnn / zznz / e / YiAi by weight, the Mg2Si crystallization phase forms, which reduces processability during hot rolling and has a negative effect. The presence of the Mg2Si phase is highly undesirable since it does not dissolve during homogenization quenching. Prototypes Eight alloys were produced under laboratory conditions, the chemical composition of which is shown in Table 1. The alloys were prepared in a laboratory induction furnace, with each casting having a mass of at least 14 kg. The following materials were used as filler materials (wt%): aluminum A99 (99.99% Al), magnesium Mg90 (99.90% Mg), and alloy compositions Al-10% Mn, Al-10% Fe, Al-10% Cr, Al-5% Zr, Al-5% Ti, Al-3% V, Al-2% Se, and Al-10% Si. The cross-section of the cast ingots was 200 x 50 mm, and the length was approximately 250 mm. The estimated cooling rate of the alloys in the solidification range did not exceed 2 K / s. zzcnnn / zznz / e / YiAi Table 1. Chemical composition of the experimental alloys (% by weight) No Mg Mn Fe Cr Zr Ti V Se Si Al 1 3.8 0.2 0.01 0.01 0.03 0.01 - - 0.25 Remainder 2 4.0 1.0 0.08 0.18 0.06 0.15 0.02 0.28 0.18 Remainder 3 4.1 0.5 0.15 0.10 0.16 0.02 - 0.01 0.09 Remainder 4 5.0 0.6 0.15 0.13 0.10 0.08 - 0.10 0.11 Remainder 5 5.1 0.5 0.16 0.12 0.16 05 0.04 - 0.10 Remainder 6 5.1 0.5 0.25 0.12 0.08 0.08 0.06 0.06 0.08 Remaining 7 5.5 0.6 0.15 0.08 0.10 0.09 - 0.10 0.10 Remaining 8 5.8 1.1 0.27 0.19 0.18 0.17 - 0.31 0.07 Remaining The molten ingots were homogenized under conditions where the maximum heating and holding temperature did not exceed 425 °C. The ingots were then hot- and cold-rolled into sheets according to the following scheme: hot rolling at 450 °C and 90% total strain to a thickness of 5 mm, intermediate quenching of the hot-rolled profile at 400 °C, and cold rolling with 30% total strain to a thickness of 3.5 mm. The mechanical properties of the sheets were determined after quenching at 300 °C for 3 hours, and the results are shown in Table 2. The mechanical properties were evaluated based on the results of the ultimate tensile strength (UTS), yield strength (YS), and elongation (El). The reference length of the flat samples was 50 mm and the test speed was 10 mm / min. zzcnnn / zznz / e / YiAi Table 2 - Tensile mechanical properties of the experimental alloys (Table 1) after quenching at 300 °C No* YS, MPa UTS, MPa El, % 1 124 282 27 2 283 372 19 3 251 367 21 4 273 382 16 5 264 390 16 6 260 381 15 7 282 394 15 g** - - - * - see chemical composition in Table 1 ** - cold rolling break The amount of precipitation was determined using computer and experimental methods, specifically using the Thermocalc software package and analysis of the structure of homogenized ingots and tempered sheets of the experimental compositions. The results are shown in Table 3. Table 3 — Rainfall amount Ll2(% by volume) and redistribution of Zr, V and Se among the structural components No* Volume fraction of Ll2 precipitation particles, % Percentage of element-forming precipitation with the LI2 type lattice, % Zr Se 1 0.02 50 - 2 0.76 75 98 3 0.20 91 80 4 0.36 85 95 5 0.24 91 - 6 0.18 81 92 7 0.35 85 95 The results show that only compositions 2-7 meet the requirements for the required strength properties. Composition 8 broke during the hot deformation process due to the presence of primary crystals of the AL6 (Fe, Mn) phase. Thus, it is shown that the claimed alloy provides high processability during the deformation process, while increasing the mechanical properties of the alloy due to precipitation of the Zr-containing phase with the LI2-type crystal lattice. The scope of protection, in the form of the following set of features, suggests in itself: 1. An aluminum alloy with a structure consisting of an aluminum solution, precipitates, and a eutectic phase, formed by elements such as magnesium, manganese, iodine, chromium, zirconium, titanium, and vanadium, characterized in that the alloy further contains silica and scandium, and at least 75% of each element in the zirconium and scandium group forms precipitates with the LI2-type lattice in an amount of at least 0.18% by volume and a particle size of no more than 20 nm, with the following redistribution of the alloying elements (% by weight): Magnesium 4.0-5.5 Manganese 0.3-1.0 Iron 0.08-0.25 Chromium 0.08-0.18 Zirconium 0.06-0.16 Titanium 0.02-0.15 Vanadium 0.01-0.06 Scandium 0.01-0.28 Silica 0.08-0.18 Aluminum and unavoidable impurities remainder. 2. Material based on the aluminum alloy according to claim 1 for the manufacture of products that operate in corrosive environments under high loads. 3. Material according to claim 2, characterized by a high level of mechanical properties after tempering, namely, ultimate tensile strength of not less than 350 MPa, yield strength of not less than 250 MPa and elongation of not less than 15%

Claims

1. An aluminum alloy with a structure consisting of an aluminum solution, precipitates, and a eutectic phase, formed by elements such as magnesium, manganese, iron, chromium, zirconium, titanium, and vanadium, characterized in that the alloy further contains silica and scandium, and at least 75% of the participation of each element in the zirconium and scandium group forms precipitates with the LI2-type lattice in an amount of at least 0.18% by volume and a particle size of no more than 20 nm, with the following distribution of alloying elements (% by weight): Magnesium 4.0-5.5, Manganese 0.3-1.0, Iron 0.08-0.25, Chromium 0.08-0.18, Zirconium 0.06-0.16, Titanium 0.02-0.15, Vanadium 0.01-0.06 Scandium 0.01-0.28 Silica 0.08-0.18 Aluminum and unavoidable impurities remainder.

2. Material based on the aluminum alloy according to claim 1 for manufacturing products that operate in corrosive environments under high loads.

3. Material according to claim 2, characterized by a high level of mechanical properties after tempering, namely, maximum tensile strength of not less than 350 MPa, yield strength of not less than 250 MPa and elongation of not less than 15%.