RU2797459C1 - Aluminium alloy and product made from it - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to the field of metallurgy of aluminium - copper - magnesium - lithium alloys used for the manufacture of semi-finished products and products used as structural materials for aerospace technology. The aluminium-based alloy contains, wt.%: lithium 1.4-1.6; copper 1.6-2.0; magnesium 0.7-1.1; manganese 0.01-0.2; zinc 0.01-0.3; zirconium 0.04-0.2; scandium 0.003-0.15; calcium 0.02-0.15; beryllium up to 0.01; aluminium - the rest.

EFFECT: invention is aimed at increasing the ductility of the alloy while maintaining the level of strength characteristics, which makes it possible to produce thin sheets, thin-walled profiles and stampings while reducing the labour intensity of production and improving the performance of products made from an aluminium alloy of the above composition.

2 cl, 2 tbl, 3 ex

Description

The invention relates to the field of metallurgy of aluminum-based alloys, in particular to aluminum-copper-magnesium-lithium alloys used for the manufacture of semi-finished products used as structural materials for aerospace technology and transport engineering.

Known alloy based on aluminum system aluminum - copper - magnesium - lithium, containing, wt.%:

Lithium 1.7-2.0 Copper 1.6-2.0 Magnesium 0.7-1.1 Zirconium 0.04-0.16 Beryllium 0.02-0.2 Manganese 0.01-0.4 Zinc 0.01-0.3 Aluminum Rest

(Patent RF No. 2180928, IPC 7 S22S 21/00, S22S 21/16, publication date 03/27/2002).

The disadvantages of this alloy are its reduced technological ductility, high labor intensity of manufacturing and low yields suitable for the manufacture of semi-finished products and products from it, toxicity, instability of mechanical properties in different batches of semi-finished products with different lithium content.

The reasons for the occurrence of the above disadvantages when using a known alloy include the fact that in a known alloy, a relatively high content of lithium leads to the formation of strengthening phases that reduce the ductility of the alloy while increasing its strength characteristics, which leads to increased rejection due to increased cracking, rejection on clips and flatness during finishing operations.

The high content of lithium leads to its excess in excess of the concentration necessary to create the Al ₃ Li(δ') and Al ₂ CuLi (T ₁ ) phases, and, since excess lithium can be in the solid solution in the form of a neutral atom and in the form of an ion in as an interstitial or substitution element, while the lattice parameters differ significantly, this leads to instability of mechanical properties, and at temperatures of deformation and heat treatment into a solid solution, the solid solution decomposes with the release of excess lithium with the formation of stable compounds that reduce the ductility of the alloy.

Known alloy based on aluminum system aluminum - copper - magnesium - lithium, containing, wt.%:

Lithium 1.5-1.9 Magnesium 1.2-3.5 Copper 1.4-1.8 Zinc 0.01 - 1.2 Manganese 0.01-0.8 Scandium 0.01-0.3 Zirconium 0.03 - 0.15 Beryllium 0.001-0.2 Aluminum Rest

(Patent of the Russian Federation No. 2296176, IPC 7 С22С 21/06, publication date 03/27/2007).

The disadvantages of this alloy are its reduced technological ductility, high labor intensity of manufacture and low yields suitable for the manufacture of semi-finished products and products from it, toxicity, instability of mechanical properties.

The reasons for the occurrence of the above disadvantages when using a known alloy include the fact that the known alloy has a high total content of lithium and magnesium, which leads to high solid solution hardening during process heating and high dislocation hardening during cold deformation, resulting in increased resistance deformation and the destruction of the semi-finished product occurs in the process of pressure treatment. In addition, an increased content of beryllium leads, most intensively during the melting process, to the release of vapors and aerosols of beryllium, which have toxic properties.

The closest alloy in terms of chemical composition and purpose to the claimed alloy based on aluminum of the system aluminum - copper - magnesium - lithium is an alloy containing, wt.%:

Lithium 1.6-1.9 Copper 1.3-1.5 Magnesium 0.7-1.1 Zirconium 0.04-0.2 Beryllium 0.02-0.2 Manganese 0.01-0.2 Zinc 0.01-0.3 Calcium 0.005-0.02 Scandium 0.005-0.01 Aluminum Rest

(Patent RF No. 2310005, IPC 7 S22S 21/00, publication date 11/10/2007).

The disadvantage of this alloy, taken as a prototype, are its reduced technological ductility, high labor intensity of manufacturing and low yields suitable for the manufacture of semi-finished products and products from it, toxicity, instability of mechanical properties.

The reasons for the occurrence of the above disadvantages when using a known alloy, taken as a prototype, include the fact that the known alloy has a high content of lithium and a low content of copper, which leads to an unfavorable ratio of the main strengthening phases δ'(Al3Li) and T' ₁ ( A12CuLi), while an increased content of the δ'(A13Li) phase negatively affects the plastic characteristics of semi-finished products, which leads to increased rejection due to increased cracking, rejection by clamps and non-flatness during finishing operations, and an increased content of beryllium leads, especially in the melting process, to the release of vapors and aerosols of beryllium, which have toxic properties.

The problem to which the invention is directed is to develop an aluminum-based alloy intended for the manufacture of semi-finished products and products for aerospace technology from it, free from the disadvantages listed above and inherent in known technical solutions.

The technical result achieved in the implementation of the invention is to obtain an alloy with increased ductility, which will improve its manufacturability, increase the yield and reduce the complexity of manufacturing semi-finished products and products while maintaining the required strength and performance characteristics of the alloy required for structural materials for aerospace technology, and also improve the sanitary and hygienic conditions for the production of semi-finished products and products from the proposed alloy.

The task with the achievement of the mentioned technical result in the implementation of the invention is solved by the fact that the known aluminum-based alloy contains lithium, copper, magnesium, manganese, zinc, zirconium, scandium, calcium, beryllium, in the following ratio of components, wt.%:

Lithium 1.4-1.6 Copper 1.6-2.0 Magnesium 0.7-1.1 Manganese 0.01-0.2 Zinc 0.01-0.3 Zirconium 0.04-0.2 Scandium 0.003-0.15 Calcium 0.02-0.15 Beryllium up to 0.01 Aluminum Rest

The proposed alloy based on aluminum, used for the manufacture of semi-finished products and products, differs from the prototype in a lower content of lithium and beryllium, a higher content of copper, scandium and calcium.

It has been established that an increased content of copper and a reduced content of lithium in the indicated ratios leads to an optimal ratio of the main strengthening phases δ'(Al3Li) and T' ₁ (A12CuLi) and, as a consequence, to an increase in properties.

Reducing the beryllium content in the alloy to 0.01 wt.% and below can significantly reduce the release of its vapors and aerosols during melting in industrial premises, while the beryllium content is within the range that allows the use of this alloy for the manufacture of civilian products.

Increasing the calcium content to 0.15 wt.%, allows you to protect the melt from oxidation, which is one of the purposes of beryllium, the content of which is reduced, and also increases the ductility and weldability of the alloy, due to the formation of a dense protective oxide film, exceeding in its protective properties the film formed beryllium, as well as Al ₃ Ca phases, which contribute to additional grain slip during deformation.

We have found that the content of scandium within the specified limits leads to an increase in the strength properties of semi-finished products, due to an increase in the dislocation hardening of the alloy during deformation due to the anti-recrystallization properties of scandium.

Various semi-finished products can be made from the proposed aluminum-based alloy: sheets and plates, stampings, pressed products. From the semi-finished products of the proposed alloy, various products can be obtained, for example: panels for covering the fuselage structures of aircraft, elements of the power set, welded fuel tanks and other elements of aerospace technology.

In the proposed product, made of an alloy based on aluminum used for the manufacture of semi-finished products, the technical result is achieved by the fact that an alloy is used as the workpiece material in the following ratio, wt.%: lithium 1.4-1.6; copper 1.6-2.0: magnesium 0.7-1.1: manganese 0.01-0.2: zinc 0.01-0.3; zirconium 0.04-0.2; scandium 0.003-0.15; calcium 0.02-0.15; beryllium up to 0.01 and aluminum - the rest.

Implementation example:

Under industrial conditions, from each alloy, the chemical composition of which is given in Table 1, flat ingots with dimensions of 390 × 1360 mm and round ingots with diameters of 200 and 350 mm were cast.

Alloy No. 1 corresponds to the alloy adopted as a prototype, alloys No. 2, 3 correspond to the proposed.

The melting of the charge, refining and casting of ingots was carried out at a temperature of 710-730°C.

Example 1

Subsequently, sheets were made from flat ingots of each alloy. The sheets were produced according to one technological scheme: hot rolling at a temperature of 440-460°C to a thickness of 6.0 mm with rolling into rolls, preliminary annealing of the rolls for 60 minutes at T = 420-440°C, cold rolling to a thickness of 1.5 mm.

When rolling a sheet of alloy No. 1 during the last pass, the strip broke along a deep flaw. The roll is divided into 2 parts and rolled out to the final thickness.

Sheets from alloys No. 2, 3 were rolled without breaks to a thickness of 1.5 mm.

Further finishing operations - smoothing and straightening of sheets by tension from alloys No. 2, 3, in comparison with alloy No. 1, were more successful and with less rejection at the final acceptance due to defects.

The yield in the production of sheets from alloys No. 2, 3 was higher by 8% than from alloy No. 1.

Subsequently, samples from sheets No. 1, 2, 3 were tested under static tension with the determination of tensile strength (σ _in ), yield strength (σ _0.2 ), relative elongation (δ, %) on samples cut along and across relative to the rolling direction .

The results of mechanical tests are presented in table 2.

Table 2 shows that the proposed alloy is superior to the known alloy (prototype) in terms of plasticity characteristics while maintaining the required strength characteristics.

Example 2

Profiles were made from round ingots with a diameter of 190 mm of each alloy (corners with a thickness of shelves up to 4 mm.).

Profiles from different alloys were made according to the same technological scheme: pressing at a temperature of 410°C, hardening of profiles in water, aging at a temperature of 150°C.

The yield of products suitable for the production of profiles from alloys No. 2, 3 was higher by 6% than from alloy No. 1.

Example 3

Forgings with a wall thickness of 50 mm were made from round ingots with a diameter of 350 mm of each alloy.

Forgings from different alloys were made according to the same technological scheme: blank forging at a temperature of 410°C, preliminary forging at a temperature of 410°C, final forging at a temperature of 400°C, hardening at a temperature of 500°C, and aging at a temperature of 150°C.

The yield in the production of stampings from alloy No. 2, 3 was higher by 5% than from alloy No. 1.

Thus, the proposed alloy achieves the set goal - improving the plasticity characteristics of the alloy and, as a result, increasing its manufacturability, increasing the yield in the production of semi-finished products and products from it, reducing the labor intensity of production, as well as improving sanitary and hygienic working conditions.

Claims (3)

1. An aluminum-based alloy containing lithium, copper, magnesium, manganese, zinc, zirconium, scandium, calcium, beryllium in the following ratio, wt.%: Lithium 1.4-1.6 Copper 1.6-2.0 Magnesium 0.7-1.1 Manganese 0.01-0.2 Zinc 0.01-0.3 Zirconium 0.04-0.2 Scandium 0.003-0.15 Calcium 0.02-0.15 Beryllium up to 0.01 Aluminum rest 2. An aluminum-based alloy product, characterized in that it is made in the form of a blank for a structural material made of an aluminum-based alloy containing components in the following ratio, wt.%: lithium 1.4-1.6; copper 1.6-2.0; magnesium 0.7-1.1; manganese 0.01-0.2; zinc 0.01-0.3; zirconium 0.04-0.2; scandium 0.003-0.15; calcium 0.02-0.15; beryllium up to 0.01; aluminum - the rest.