Aluminum-based alloy

Abstract

The invention relates to an aluminum-based alloy. The invention relates to the field of metallurgy of aluminum-based materials and can be used for manufacturing products operating in highly loaded corrosive environments, in particular at high and low temperatures. A new aluminum alloy is claimed. It contains magnesium, manganese, iron, chromium, zirconium, titanium, vanadium, silicon and scandium, wherein at least 75% of the share of each element from the group of zirconium and scandium forms L12-type secondary precipitates, the amount of which is at least 0.18% by volume and the particle size does not exceed 20 nm.

Description

[0001] This application is a divisional application. The international application number of the original application is PCT / RU2019 / 001038, the application date is December 27, 2019, the Chinese national phase application number is 201980093361.6, and the invention title is "Aluminum-based Alloy". Technical Field

[0002] This invention relates to the field of aluminum-based material metallurgy and can be used to manufacture products (including welded structures) that operate under high loads in corrosive environments (humid atmospheres, fresh water, seawater, etc.), particularly at high and low temperatures. The material can be produced in the form of rolled products, such as slabs, plates and rolled sheets, extruded profiles and tubes, forgings, other forged semi-finished products, as well as powders, flakes, granules, etc.

[0003] The proposed alloys are primarily used in transportation vehicles, such as hulls and hull components of ships and other vessels, as well as coatings and other loading components of aircraft, trucks, and railway tank cars, particularly for transporting chemically active substances, and in the food industry, among other applications. Background Technology

[0004] Due to their high corrosion resistance, weldability, high elongation values, and ability to operate at low temperatures, Al-Mg malleable alloys (5xxx series) have been widely used in products that operate in corrosive environments; in particular, they are intended for use in rivers and seawater (water transport, pipelines, etc.) and in tanks for transporting liquefied gases and chemically active liquids.

[0005] The main drawback of the 5xxx series alloys is the low strength performance of the annealed forged semi-finished products; for example, the yield strength of the 5083 alloy after annealing is usually no more than 150 MPa (see "Industrial Aluminum Alloys: Reference Book". S. G.A. Liev, B.M. Maltman, S.M. M.M. B.M. Suyan, et al. Moscow: Metallurgy, 1984).

[0006] One method to improve the strength properties of annealed alloys 5xxx is through additional alloying with transition metals, with Zr and smaller amounts of Hf, V, Er, and some other elements being most widely used. In this case, the main distinguishing feature of this alloy from other known alloys in the (5083 type) Al-Mg system is the content of elements forming dispersions, particularly those with L12-type lattices. In this case, the combined effect of improved strength properties is achieved through solution hardening of the aluminum solid solution (primarily magnesium) and the presence of various secondary phases in the structure of precipitates formed during homogenization (heterogeneous) annealing.

[0007] Therefore, the alloy that Alcoa claims protection for is known (RU Patent 2431692). The material comprises (by weight percentage, i.e., wt%): 5.1-6.5% magnesium, 0.4-1.2% manganese, 0.45-1.5% zinc, up to 0.2% zirconium, up to 0.3% chromium, up to 0.2% titanium, up to 0.5% iron, up to 0.4% silicon, 0.002-0.25% copper, up to 0.01% calcium, up to 0.01% beryllium; at least one of the following elements: boron, carbon, each up to 0.06%; at least one of the following elements: bismuth, lead, tin, each up to 0.1%; scandium, silver, lithium, each up to 0.5%; vanadium, cerium, yttrium, each up to 0.25%; at least one of the following elements: nickel and cobalt, each up to 0.25%; the balance being aluminum and unavoidable impurities, wherein the total content of magnesium and zinc is 5.7-7.3% by weight, the total content of iron, cobalt and / or nickel is not more than 0.7% by weight, and the balance being aluminum and unavoidable impurities. Among the drawbacks of this alloy, the overall level of strength properties is relatively low, which can sometimes limit its use. The presence of numerous minor additives can reduce productivity, thus adversely affecting the performance of casting facilities, while the high magnesium content leads to decreased machinability and corrosion resistance.

[0008] The combined use of scandium and zirconium additives achieves a much greater improvement in strength properties than in the 5083 alloy. In this case, this effect is achieved by forming a very large number of precipitates (typically 5nm-20nm in size), which are resistant to high-temperature heating during the deformation processing of the forged semi-finished product and subsequent annealing, thus providing a higher level of strength properties.

[0009] For example, a material based on an aluminum-magnesium system is known, which is alloyed with zirconium and scandium additives; specifically, CRISM "Prometey" claims a material disclosed in RU Patent 2268319, referred to as Alloy 1575-1. This alloy is characterized by a higher level of strength properties than alloys of type 5083 and 1565. The claimed material comprises (by weight percentage): 5.5%-6.5% magnesium, 0.10%-0.20% scandium, 0.5%-1.0% manganese, 0.10%-0.25% chromium, 0.05%-0.20% zirconium, 0.02%-0.15% titanium, 0.1%-1.0% zinc, 0.003%-0.015% boron, 0.0002%-0.005% beryllium, with the balance being aluminum. Among the disadvantages of this material, attention should be paid to the high magnesium content, which can sometimes adversely affect the machinability during deformation processing, and in some cases, the presence of the β-Al8Mg5 phase in the final structure leads to a reduction in corrosion resistance.

[0010] The material claimed in Kaiser Aluminium's U.S. Patent 6,139,653 is also known. The claim refers to an alloy based on an Al-Mg-Sc system, which also contains elements selected from hafnium (Hf), manganese (Mn), zirconium (Zr), copper (Cu), and zinc (Zn), particularly 1.0%–8.0% (wt%) magnesium (Mg), 0.05%–0.6% scandium (Sc), and 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 certain versions, the material may additionally contain 0.1%–0.8% (wt%) Mn. Among the disadvantages of the claimed material, it should be noted that the strength properties are relatively low at the lower limit of magnesium content, while corrosion resistance and machinability during deformation processing are low at the upper limit of magnesium content. At the same time, in order to ensure high-level performance, it is necessary to adjust the size ratio of the particles formed by elements such as Sc, Hf, Mn and Zr.

[0011] The material claimed by Alcoa and described in U.S. Patent 5,624,632 is known. This aluminum-based alloy comprises (by weight%): 3%–7% magnesium, 0.05%–0.2% zirconium, 0.2%–1.2% manganese, up to 0.15% silicon, and approximately 0.05%–0.5% precipitate-forming elements selected from Sc, Er, Y, Cd, Ho, and Hf; the balance being aluminum and foreign elements and impurities. A disadvantage is that when using a lower range of alloying elements, attention should be paid to relatively lower values ​​for strength properties.

[0012] The RUSAL material described in patent RU2683399c1 is known. This aluminum-based alloy contains (by weight%): 0.10%-0.50% zirconium, 0.10%-0.30% iron, 0.40%-1.5% manganese, 0.15%-0.6% chromium, 0.09%-0.25% scandium, 0.02%-0.10% titanium, and at least one element selected from: 0.10%-0.50% silicon, 0.10%-5.0% cerium, 0.10%-2.0% calcium, and optionally 2.0%-5.2% magnesium.

[0013] NanoAl claims protection and describes the material in application WO2018165012. This alloy comprises aluminum, magnesium, manganese, silicon, zirconium, and Al3Zr L12 nanoparticles with an average particle size of approximately 20 nm, in a content of 20%. 211 / m³ or higher; furthermore, the particles contain one or more elements selected from tin, strontium, and zinc; the work-hardened aluminum alloy has a yield strength of at least about 380 MPa, an ultimate tensile strength of at least about 440 MPa, and an elongation at room temperature of at least about 5%, while the annealed aluminum alloy has a yield strength of at least about 190 MPa, an ultimate tensile strength of at least about 320 MPa, and an elongation at least about 18%. Among the disadvantages of conditional alloys, the low strength level in the annealed state should be noted.

[0014] The prototype is a technical solution known from an invention under U.S. Patent 6531004 to Eads Deutschland GmbH. Specifically, a weldable corrosion-resistant material having three phases of Al, Zr, and Sc primarily comprises (by weight%): 5%-6% magnesium, 0.05%-0.15% zirconium, 0.05%-0.12% manganese, 0.01%-0.2% titanium, a total of 0.05%-0.5% scandium and terbium, and optionally at least one additional element selected from several lanthanides, wherein scandium and terbium are mandatory elements, and at least one element selected from 0.1%-0.2% copper and 0.1%-0.4% zinc; the balance being unavoidable impurities of aluminum and no more than 0.1% silicon. Among the disadvantages of this material, the presence of rare and expensive elements should be noted. Furthermore, this material does not adequately withstand high-temperature heating during process heating. Summary of the Invention

[0015] The purpose of this invention is to create a new high-strength aluminum alloy characterized by low cost, a high level of physical and mechanical properties, machinability and corrosion resistance, especially high mechanical properties after annealing (temporary resistance minimum of 350 MPa, yield strength minimum of 250 MPa, elongation minimum of 5%) and high machinability during hot and cold deformation.

[0016] The technical effect is to solve the above objectives, ensure high machinability during deformation processing, and improve the mechanical properties of the alloy due to the precipitation of Zr-containing phases with L12-type lattice.

[0017] The achievement of this objective and the specified technical effect are ensured by the following fact: A claim is made for an alloy comprising magnesium, manganese, iron, chromium, zirconium, titanium, vanadium, silicon, and scandium, wherein at least 75% of each element from the group consisting of zirconium and scandium forms L12-type secondary precipitates, the amount of which is at least 0.18% by volume and the particle size is not more than 20 nm, and the alloying elements have the following concentrations 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 0.02-0.06 Scandium 0.01-0.28 Silicon 0.06-0.18 Aluminum and unavoidable impurities remain.

[0018] Surprisingly, the improved strength performance was found to be due to the combined positive effects of magnesium and secondary alloys containing manganese, chromium, zirconium, scandium, and vanadium, which exhibit high-temperature resistance and solid solution hardening of the aluminum solution. Simultaneously, the reduced solubility of zirconium and scandium in the aluminum solution due to the additional alloying with silicon and vanadium increased the volume fraction of precipitate particles with a maximum size of 20 nm, thereby improving the hardening efficiency.

[0019] In this case, the aluminum alloy structure must contain minimally alloyed aluminum solution and precipitate particles, particularly Al6Mn phase with a maximum size of 200 nm, Al7Cr phase with a maximum size of 50 nm, and Al3Zr and / or Al3(Zr,Sc) and / or Al3(Zr,V) type particles with an L12 lattice with a maximum size of 20 nm.

[0020] The rationale for the required alloy composition to ensure a given structure is achieved in the alloy is given below.

[0021] Due to solution hardening, 4.0%–5.5% magnesium is required to improve the overall level of mechanical properties. If the magnesium content exceeds the specified level, the effect of this element will lead to reduced machinability during metal processing, for example, having a significant negative impact on the yield ratio during deformation when rolling ingots. A content below 4% wt will not provide the minimum required strength performance level.

[0022] 0.06 wt%–0.16 wt% zirconium is required to ensure dispersion hardening and to form precipitates of Al3Zr L12 or Al3(Zr,Sc) and / or Al3(Zr,V) type phases in the presence of relevant elements.

[0023] The amounts of scandium and vanadium, at 0.01 wt%–0.28 wt% and 0.01 wt%–0.06 wt% respectively, are necessary to ensure the required strength performance level, because dispersion hardening forms metastable precipitates that also contain zirconium with an L12 lattice.

[0024] Typically, zirconium, scandium, and vanadium redistribute between an aluminum matrix and precipitates of a metastable Al3Zr phase with an L12 lattice, and the number of particles is determined by the solubility of these elements at the decomposition temperature.

[0025] If the zirconium concentration in the alloy is higher than 0.16% by weight, an increased melting temperature is required, which is technically not feasible in some cases under the semi-continuous casting conditions of ingots.

[0026] When using standard casting conditions with a zirconium content greater than 0.16% by weight, it is possible to form a D0 structure in the primary crystal structure. 23 A phase with a lattice-like structure is unacceptable.

[0027] Because the amount of secondary phase precipitates with an L12 lattice is insufficient, zirconium, scandium, and vanadium contents below the specified levels will not provide the minimum required strength performance level.

[0028] A chromium content of 0.08 wt%–0.18 wt% is necessary to improve the overall level of mechanical properties due to dispersion hardening caused by the formation of the secondary phase with Al7Cr. If the chromium content exceeds the specified level, the effect of this element will lead to reduced machinability during metal processing, for example, in rolling ingots, it has a significant negative impact on the yield ratio during deformation. A content below 0.1 wt% will not provide the minimum required strength performance level.

[0029] A manganese content of 0.4 wt%–1.0 wt% is necessary to improve the overall level of mechanical properties due to dispersion hardening caused by the formation of the secondary phase with Al6Mn. If the manganese content exceeds the specified level, the effect of this element will lead to reduced machinability during metal processing, for example, during rolling ingots, as the potential formation of primary crystals can significantly negatively impact the yield ratio during deformation. Contents below 0.3 wt% will not provide the minimum required strength performance level. When the content exceeds 1.0 wt%, primary crystals of the Al6Mn phase will form, reducing machinability during deformation processing.

[0030] Silicon is needed to reduce the solubility of zirconium, scandium, and vanadium in molten aluminum; therefore, the main role of these elements will be related to the increased supersaturation of zirconium, scandium, and vanadium in molten aluminum during billet casting. This will ensure the release of more secondary phase dispersions with an L12 lattice during subsequent homogenization annealing, improving the dispersion hardening effect. Furthermore, it has been experimentally determined that in the presence of silicon, less than 75% zirconium and scandium content in the alloy (within the concentration range of the claimed alloying elements) results in at least 0.18% by volume precipitates with an L12 lattice. When the silicon content is below 0.08% by weight, it has no effect on the solubility of zirconium and scandium in molten aluminum. When the content exceeds 0.18% by weight, a Mg2Si crystalline phase forms, reducing workability during hot rolling and having an adverse effect. The presence of the Mg2Si phase is highly undesirable because it does not dissolve during homogenization annealing. Detailed Implementation

[0031] Eight alloys were prepared under laboratory conditions, and their chemical compositions are shown in Table 1.

[0032]

[0033] Table 1: Chemical composition (wt%) of the experimental alloys

[0034] The alloy was prepared in a laboratory induction furnace, with each casting weighing at least 14 kg. The following materials were used as charge (by weight%): Aluminum A99 (99.99% Al), Magnesium Mg90 (99.90% Mg), and the following alloy composition: Al-10%Mn, Al-10%Fe, Al-10%Cr, Al-5%Zr, Al-5%Ti, Al-3%V, Al-2%Sc, and Al-10%Si. The ingot cross-section was 200 x 50 mm, with a length of approximately 250 mm. The estimated alloy cooling rate during solidification did not exceed 2 K / s.

[0035] The ingots were homogenized under conditions where the maximum heating and holding temperature did not exceed 425°C. The ingots were then hot-rolled and cold-rolled into plates according to the following scheme: hot rolling at 450°C with 90% total deformation to a thickness of 5 mm; intermediate annealing of the hot-rolled billet at 400°C; and cold rolling with 30% total deformation to a thickness of 3.5 mm. The mechanical properties of the plates were measured after annealing at 300°C for 3 hours, and the results are shown in Table 2. The mechanical properties were evaluated based on the measured results of ultimate tensile strength (UTS), yield strength (YS), and elongation (E1).

[0036] The gauge length of the flat sample is 50 mm, and the testing speed is 10 mm / min.

[0037] See Table 1 for chemical composition. Cracking during cold rolling Table 2: Mechanical tensile properties of the experimental alloys (Table 1) after annealing at 300℃ The amount of precipitates was determined using computational and experimental methods, particularly the Thermocalc software package and structural analysis of homogenized ingots and annealed plates of the experimental components. The results are shown in Table 3.

[0038]

[0039] Table 3: Amount of precipitate L12 (volume percentage) and redistribution of Zr, V and Sc in structural components

[0040] The results show that only compositions 2-7 meet the strength performance requirements. Due to the presence of primary Al6(Fe,Mn) phase crystals, composition 8 cracked during hot deformation processing.

[0041] Therefore, it has been shown that the claimed alloy provides high machinability during deformation processing, while the mechanical properties of the alloy are improved due to the Zr-containing precipitates with an L12-type lattice.

[0042] The following set of features constitutes the scope of protection: 1. An aluminum alloy comprising magnesium, manganese, iron, chromium, zirconium, titanium, vanadium, silicon, and scandium, wherein at least 75% of each element from the group consisting of zirconium and scandium forms L12-type secondary precipitates, said precipitates being at least 0.18% by volume and having a particle size not exceeding 20 nm, and wherein the following alloying elements have the following concentrations in weight percent: Magnesium 5.0-5.8 Manganese 0.3-1.0 Iron 0.15-0.25 Chromium 0.08-0.18 Zirconium 0.06-0.16 Titanium 0.02-0.15 Vanadium 0.01-0.06 Scandium 0.01-0.10 Silicon 0.11-0.18 Aluminum and unavoidable impurities remain.

Claims

1. An aluminum alloy comprising magnesium, manganese, iron, chromium, zirconium, titanium, vanadium, silicon, and scandium, wherein, At least 75% of each element from the group consisting of zirconium and scandium forms L12-type secondary precipitates, said precipitates being at least 0.18% by volume and having a particle size not exceeding 20 nm, and the following alloying elements having the following concentrations by weight: Magnesium 5.0-5.8 Manganese 0.3-1.0 Iron 0.15-0.25 Chromium 0.08-0.18 Zirconium 0.06-0.16 Titanium 0.02-0.15 Vanadium 0.01-0.06 Scandium 0.01-0.10 Silicon 0.11-0.18 Aluminum and unavoidable impurities remain.

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