RU2327758C2 - Aluminium base alloy and products made out of it - Google Patents

Abstract

FIELD: metallurgy; high resistant aluminium alloys.

SUBSTANCE: alloy and a product out of this alloy contain the following elements, mas.%: copper 2.1-2.4; lithium 1.5-2.0; magnesium 0.6-1.0; zinc 0.1-1.0; zinc 0.1-1.0; scandium 0.15-0.2; zirconium 0.05-0.2; iron 0.02-0.15; manganese 0.01- 0.2; beryllium 0.005-0.2; calcium 0.001-0.05; at least one element out of the group titanium 0.01-0.1; nickel 0.001- 0.01; vanadium 0.005-0.01; at limiting silicon content up to 0.1; chromium to 0.05; sodium to 0.001; gallium to 0.001; aluminium - the rest.

EFFECT: there obtained an alloy and a product made out of it which possess high strength and plasticity.

2 cl, 2 tbl, 3 ex

Description

The invention relates to the field of metallurgy, in particular to high-strength aluminum alloys of the aluminum-copper-magnesium-lithium system used for the manufacture of products used in critical aerospace structures.

It is known that aluminum-lithium alloys have a unique combination of mechanical properties, namely low density, high modulus of elasticity and a sufficiently high level of strength. The presence of these properties allows to reduce the weight of riveted and welded structures of aircraft, which makes it possible to save fuel, increase load capacity and improve other flight performance.

However, these alloys have low ductility in states close to maximum strength (Aluminum-lithium alloys. Structure and properties / Fridlyander I.N. et al .; Res. Ed. Koval Yu.N. Academy of Sciences of Ukraine. Institute of Metal Physics. - Kiev: Science.Dumka, 1992, 177 p.). Various measures were proposed to increase ductility, such as alloying with copper and magnesium, modification with zirconium and scandium, and varying various technological regimes (ibid.).

Known alloy based on aluminum of the following composition, wt.%:

Copper - 3.0-3.5

Lithium - 1.5-1.8

Zirconium - 0.05-0.12

Scandium - 0.06-0.12

Silicon - 0.02-0.15

Iron - 0.02-0.2

Beryllium - 0.0001-0.02

At least one member from the group:

Magnesium - 0.1-0.6

Zinc - 0.02-0.1

Manganese - 0.05-0.5

Germanium - 0.02-0.2

Cerium - 0.05-0.2

Yttrium - 0.005-0.02

Titanium - 0.005-0.05

Aluminum - the rest (patent No. 2180930, C22C 21/12, C22C 21/16, 2002).

The disadvantages of this alloy are the high complexity of manufacturing due to its low manufacturability; reduced yield in the manufacture of semi-finished products and products due to increased cracking; the impossibility of obtaining products from it with a minimum thickness. These disadvantages are caused by the high content of copper and silicon; the scandium content within the stated limits does not allow to fully obtain the hardening effect due to the allocation of AlSc dispersoids.

The closest chemical composition and purpose of the claimed alloy based on aluminum is an alloy composition, wt.%:

Copper - 2.5-3.5

Lithium - 1.5-1.95

Zirconium - 0.05-0.15

Scandium - 0.01-0.15

Calcium - 0.001-0.05

Chrome - 0.01-0.3

Hydrogen - 1.5 · 10 ^-5 -5.0 · 10 ^-5

At least one element from the group consisting of:

Magnesium - 0.01-0.6

Titanium - 0.005-0.009

Boron - 0.0002-0.007

Manganese - 0.005-0.6

Vanadium - 0.01-0.15

Cerium - 0.005-0.2

Iron - 0.01-0.5

And at least one element from the group containing:

Zinc - 0.01-0.8

Tin - 0.005-0.1

Nickel - 0.005-0.15

Beryllium - 0.0001-0.2

Sodium - 0.0003-0.001

Aluminum - the rest (patent No. 2163940, C22C 21/12, 2001).

The disadvantages of this alloy, taken as a prototype, are its relatively low adaptability, the result of which is the high complexity of manufacturing and low yield.

The reasons for the occurrence of these disadvantages include an increased copper content, which leads to the formation of coarse irregular intermetallic compounds inside grains and at their boundaries, which are copper-containing phases formed during crystallization of the alloy in areas with a high copper content. These phases are not individual particles, but vast accumulations that impede shear deformations during pressure treatment, which leads to a significant decrease in the ductility of the alloy. In addition, the presence of simultaneously zirconium, scandium and chromium in the alloy leads to the formation of coarse intermetallic phases, which reduce the level of mechanical properties of the alloy, which negatively affects its manufacturability.

The technical problem to which the invention is directed is to obtain an aluminum-based alloy having high tensile strengths and ductility.

The technical result that can be obtained by carrying out the invention:

- improving the manufacturability of the alloy by increasing the mechanical characteristics;

- reduction of rejects on cracks, and therefore, increase in yield;

- the manufacture of semi-finished products with a minimum thickness.

All of the above will allow the use of the proposed alloy for the manufacture of semi-finished products and products from them used in the construction of aircraft, while maintaining the required plastic and operational characteristics for structural materials for aerospace engineering.

The specified technical result is achieved by the fact that the proposed aluminum alloy containing copper, lithium, magnesium, zinc, scandium, zirconium, iron, manganese, beryllium, calcium, characterized in that it additionally contains silicon, with a limited content of chromium, sodium and gallium, and at least one element from the group comprising titanium, nickel, vanadium in the following ratio of components, wt.%:

copper 2.1-2.4 lithium 1.5-2.0 magnesium 0.6-1.0 zinc 0.1-1.0 scandium 0.15-0.2 zirconium 0.05-0.2 iron 0.02-0.15 manganese 0.01-0.2 beryllium 0.005-0.2 calcium 0.001-0.05

at least one element from the group

titanium 0.01-0.1 nickel 0.001-0.01 vanadium 0.005-0.01

while restricting content

silicon up to 0.1 chromium up to 0.05 sodium up to 0.001 Gaul up to 0.001 aluminum rest.

The aluminum-based alloy used for the manufacture of semi-finished products and products differs from the well-known alloy adopted for the prototype with a lower content of copper, calcium and chromium and a higher content of magnesium, zinc, and scandium.

A decrease in the copper content in the alloy to the range of 2.1-2.4 wt.% With an increase in the magnesium content to 1.0 wt.% And the corresponding combination of the contents of other elements allows copper to be almost completely converted into solid solution and contributes to the appearance of an additional hardening phase in the structure S ₁ (Al ₂ CuMg). This leads to a significant decrease in the volume fraction of intermetallic compounds of copper-containing phases (which was established by electron microscopic examination of the alloy) and, as a result, an increase in the ductility of the alloy and its strength. A decrease in the amount of copper in the alloy of less than 2.1 wt.% Does not affect the increase in its ductility characteristics, but significantly reduces the strength characteristics.

The increase in the content of scandium to 0.15-0.20 wt.%, With a zirconium content in the range of 0.05-0.20 wt.%, As well as the introduction of one or more elements from the group of titanium, nickel and vanadium in the indicated amounts promotes the formation of homogeneous fine-grained structure, provides structural hardening of semi-finished products and products from the proposed alloy, which allows to achieve the required level of strength properties of the alloy.

It was additionally established that sodium does not form phases with aluminum, which can lead to brittle fracture along grain boundaries in the processes of alloy recrystallization and pressure treatment. It was also found that when the sodium content is below 0.001 wt.%, It almost completely dissolves in the solid solution, which leads to an increase in the ductility of the alloy.

Calcium in an amount of 0.005-0.02 wt.% Is an additive that binds excess sodium and other impurity elements, leading to the formation of a more round shape of the released intermetallic compounds and their coagulation, which leads to more favorable conditions of shear deformation and, as a result, an increase in technological plasticity alloy.

Iron in the range of 0.02-0.15 wt.% Increases strength and improves creep characteristics. At the same time, the introduction of a high titanium content to 0.01-0.1 wt.% Helps to reduce the tendency of the alloy to crack formation and, in addition, due to the grinding of grain and the alignment of the properties of the alloy throughout the volume of the ingot, it leads to an additional increase in strength and ductility.

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

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 the alloy is used as the workpiece material in the following ratio of components, wt.%: Copper, 2.1-2.4; lithium 1.5-2.0; magnesium 0.6-1.0; zinc 0.1-1.0; scandium 0.15-0.2; zirconium 0.05-0.2; iron 0.02-0.15; manganese 0.01-0.2; beryllium 0.005-0.2; calcium 0.001-0.05; at least one element from the group titanium 0.01-0.1; nickel 0.001-0.01; vanadium 0.005-0.01; while limiting the silicon content to 0.1; chromium up to 0.05; sodium to 0.001; gallium up to 0.001; aluminum is the rest.

Implementation examples.

Example 1

In industrial conditions, from each alloy, the chemical composition of which is shown in Table 1, flat ingots with a cross section of 300 × 1100 mm were made by melting the mixture, refining the alloy and casting at a temperature of 710-730 ° C into a flat crystallizer (chemical composition No. 1 corresponds to the alloy, adopted as a prototype, the compositions No. 2, 3 and 4 correspond to the proposed alloy). Subsequently, clad sheets were made from the ingots of each alloy by hot rolling at a temperature of 430 ° C to a thickness of 6.5 mm with convolution into coils, annealing at a temperature of 400 ° C and cold rolling.

The alloy sheet No. 1 was only able to be rolled to a thickness of 0.9 mm and further rolling was stopped due to the presence of flaws on the side edges of the sheet with a depth of more than 30 mm and the presence of breaks in the roll.

Sheets of alloys Nos. 2, 3 and 4 were rolled without breaks to a thickness of 0.5 mm.

Further finishing operations - laying and straightening sheets by stretching - from alloys No. 2, 3 and 4 in comparison with alloy No. 1, despite their smaller thickness, were more successful and with less rejection at the final acceptance for defects (clamps, flatness and cracks) )

The yield for the production of sheets from alloys No. 2, 3 and 4 was 30% higher than that of alloy No. 1.

Subsequently, samples from sheets Nos. 1, 2, 3, and 4 were tested under static tension with the determination of tensile strength (σ _in ), yield strength (σ _0.2 ), elongation (δ,%). Samples were cut along, across and at an angle of 45 ° relative to the rolling direction.

The results of the mechanical tests are presented in table 2. The table shows that the proposed alloy is superior to the known, adopted as a prototype, in terms of strength and ductility.

Example 2

In industrial conditions, from each alloy, the chemical composition of which is given in Table 1, round ingots with diameters of 190 mm were made by melting the mixture, refining the alloy and casting into a mold at a temperature of 710-730 ° C (chemical composition No. 1 corresponds to the alloy accepted as prototype, compositions No. 2, 3 and 4 correspond to the proposed alloy). Profiles (corners with shelf thicknesses up to 5 mm) were made from ingots of each alloy by pressing at a temperature of 400 ° C, quenching in water and aging at a temperature of 150 ° C for 24 hours.

The yield for the production of profiles from alloys No. 2, 3 and 4 was 15% higher than from alloy No. 1.

Example 3

In industrial conditions, each ingot, the chemical composition of which is given in Table 1, made round ingots with diameters of 350 mm by melting the mixture, refining the alloy and casting it in a mold at a temperature of 710-730 ° C (chemical composition No. 1 corresponds to the alloy accepted as prototype, compositions No. 2, 3 and 4 correspond to the proposed alloy). Forgings with a wall thickness of 40 mm were made from ingots of each alloy by blanking at 410 ° С, preliminary stamping at 410 ° С, etching, final stamping at 400 ° С, quenching at 500 ° С for 2 hours and aging at a temperature of 150 ° C for 24 hours.

The yield in the production of stampings from alloys No. 2, 3 and 4 was 10% higher than from alloy No. 1.

Thus, the proposed alloy ensures the achievement of the technical task of increasing the strength characteristics while increasing the ductility of the alloy and, as a consequence, increasing its manufacturability. This leads to an increase in the yield suitable for the production of semi-finished products and products from it, providing the possibility of producing thin sheets, thin-walled profiles and stampings while reducing labor intensity and maintaining the required strength and operational characteristics for structural materials for aerospace engineering.

Table 1
The chemical composition of the alloys Alloy Alloy composition no. The content of components, wt.% Cu Li Mg Zn Sc Zr Fe Mn Be Sa Ti Ni V Si Cr Na Ga Al Prototype one 3.0 1.7 0.5 0.01 0.08 0.09 0.04 0.3 0.002 0.002 0,03 0.005 0.01 0.02 0.01 0,0008 - Rest Proposed 2 2,4 1,6 0.75 0.4 0.17 0.10 0.04 0.21 0.01 0.002 0,03 0.006 0.008 0.008 0.001 0,0006 0.0001 3 2,3 1.7 0.7 0.45 0.14 0.08 0.10 0.18 0,03 0.004 0,03 0.007 0.05 0,03 0.001 0,0008 0,0002 four 2.1 1,5 0.6 0.2 0.19 0,07 0.04 0.05 0.001 0.01 0.01 0.001 0.01 0.01 0.001 0,0005 0.0001

table 2
Mechanical properties of alloys Alloy Alloy Composition Number Sample cutting direction Mechanical properties σ _in , MPa σ _0.2 , MPa δ,% Prototype one Share 520 500 8.9 Transverse 510 498 8.5 At an angle of 45 ° 498 460 9.7 Proposed 2 Share 550 519 12.6 Transverse 538 512 11.8 At an angle of 45 ° 524 508 12.5 3 Share 551 521 12.8 Transverse 538 505 11.9 At an angle of 45 ° 525 509 12.9 four Share 532 515 11.9 Transverse 539 309 12.1 At an angle of 45 ° 523 508 13.1

Claims (2)

1. An aluminum-based alloy containing copper, lithium, magnesium, zinc, scandium, zirconium, iron, manganese, beryllium, calcium, chromium, sodium and at least one element from the group comprising titanium, nickel, vanadium, characterized in that it additionally contains silicon and gallium in the following ratio of components, wt.%: copper 2.1-2.4 lithium 1.5-2.0 magnesium 0.6-1.0 zinc 0.1-1.0 scandium 0.15-0.2 zirconium 0.05-0.2 iron 0.02-0.15 manganese 0.01-0.2 beryllium 0.005-0.2 calcium 0.001-0.05 at least one element from the group titanium 0.01-0.1 nickel 0.001-0.01 vanadium 0.005-0.01 while restricting content silicon up to 0.1 chromium up to 0.05 sodium up to 0.001 Gaul up to 0.001 aluminum rest 2. The product is made of an alloy based on aluminum, characterized in that it is made of an alloy of the following composition, wt.%: copper 2.1-2.4 lithium 1.5-2.0 magnesium 0.6-1.0 zinc 0.1-1.0 scandium 0.15-0.2 zirconium 0.05-0.2 iron 0.02-0.15 manganese 0.01-0.2 beryllium 0.005-0.2 calcium 0.001-0.05 at least one element from the group titanium 0.01-0.1 nickel 0.001-0.01 vanadium 0.005-0.01 while restricting content silicon up to 0.1 chromium up to 0.05 sodium up to 0.001 Gaul up to 0.001 aluminum rest