WO2007111529A1

WO2007111529A1 - Aluminium-based alloy

Info

Publication number: WO2007111529A1
Application number: PCT/RU2007/000109
Authority: WO
Inventors: Valeriy Ivanovich Popov; Boris Vladimirovich Ovsyannikov; Viktor Mikhailovich Zamyatin
Original assignee: Otkrytoe Akcionernoe Obschestvo 'kamensk-Uralsky Metallurgichesky Zavod'
Priority date: 2006-03-27
Filing date: 2007-03-07
Publication date: 2007-10-04
Also published as: PT2006403E; EP2006403A4; ES2319718T1; DE07747842T1; EP2006403A1; DE602007004465D1; RU2310005C1; US20090068056A1; ATE455874T1; ES2319718T3; EP2006403B1

Abstract

The invention relates to aluminium-based alloy metallurgy, in particular to the alloy of an alluminium-copper-magnesium-lithium system for producing semi-finished products and articles therefrom which are used in the capacity of structural materials for aerospace engineering. The aim of said invention is to improve the plasticity and processabilty of the alloys of the alluminium-copper-magnesium-lithium system, increase the yield of a material suitable for producing semifinished materials and articles made therefrom, make it possible to produce thin sheets, thin-walled sections and stampings and simultaneously to reduce labour intensity and save strength and operation characteristics of structural materials used in aerospace engineering. Said technical result is attainable by that the alloy contains elements at the following component ratio : 1.6-1.9 mass % lithium, i.3-1.5 mass % copper, 0.7-1.1 mass % magnesium, 0.04-0.2 mass % zirconium, 0.02-0.2 mass % beryllium,0.01-0.1 titanium, 0.01-o.15 mass % nickel, 0.01-0.2 manganese, up to 0.001 mass % gallium, 0.01-0.3 mass % zinc, up to 0.0005 mass % sodium, 0.005-0.02 mass % calcium and at least one element selected from a group containing of 0.005-0.01 mass % vanadium and 0.005-0.01 mass % scandium, the rest being aluminium.

Description

Aluminum Alloy

Technical field

The invention 'relates to the field of metallurgy of aluminum-based alloys, in particular to an alloy of the aluminum-copper-magnesium-lithium system used for the manufacture of semi-finished products and articles thereof used as structural materials for aerospace engineering.

It is known that aluminum - lithium alloys have a unique combination of mechanical properties, namely low density, high modulus of elasticity and sufficiently high strength characteristics. The presence of these properties makes it possible to use the alloys of this system as a structural material for aerospace engineering, which makes it possible to improve a number of flight technical characteristics of aircraft, in particular, reducing the mass of vehicles, saving fuel, increasing load capacity.

However, aluminum - lithium alloys have one drawback - low ductility in states close to maximum strength (H. I. Fridlyander., K.V. Chuistov, A. L. Berezina, N. I. Kolobnev, Aluminum-lithium alloys. Structure and properties., Kiev: Science. Dumka, 1992, p. 177). State of the art

Known aluminum-based alloy containing May. %:

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

Titanium 0.01 - 0.07

Nickel 0.02 - 0.15

Manganese 0.01 - 0.4

Aluminum Else (USSR Author's Certificate N '1767916, MKI S 22

C 21/16, publication date 1997.08.20).

The disadvantages of this alloy are its low manufacturability, the high complexity of manufacturing and low yield in the manufacture of semi-finished products and products from it, the inability to obtain from it thin sheets, thin-walled profiles and stampings.

The reasons for the occurrence of the above disadvantages when using the known alloy include the fact that in the known alloy, a relatively high copper content negatively affects the heat resistance and ductility during pressure treatment, which leads to an increased crack formation, increased rejection by clamps and non-flatness during finishing operations, namely when laying and dressing semi-finished products.

Known aluminum-based alloy - 8093, (the designation of the alloy is in accordance with the alloy numbers and complies with the definitions registered by the Aluminum Association, Washington,

USA) containing May. %:

Lithium 1.9 - 2.6

Copper 1.0 - 1.6

Magnesium 0.9 - 1.6

Zirconium 0.04 - 0.14

Titanium up to 0.1 Manganese up to 0.1

Zinc up to 0.25

Aluminum Else

(International designation of alloys and chemical composition limits of wrought aluminum and aluminum alloys, Aluminum Association: 2004, p.12, 13)

The disadvantages of this alloy are the increased cost of the alloy, its low manufacturability, high labor input and low yield in the manufacture of semi-finished products and products from it, the impossibility of obtaining thin sheets, thin-walled profiles and stampings from it.

The reasons for the occurrence of the above disadvantages when using known alloy, it refers to the fact that in the known alloy an increased lithium content having a high cost, in addition, an increased lithium content leads to the formation of hardening phases somewhat increasing the strength characteristics of the alloy, but significantly reducing its ductility during casting and pressure treatment, which leads to to increased crack formation, increased rejection by clamps and non-flatness during finishing operations, namely when laying and dressing semi-finished products.

The closest alloy in chemical composition and purpose to the claimed aluminum-based alloy is an alloy containing, wt.%:

Lithium 1.7 - 2.0

Copper 1.6 - 2.0

Magnesium 0.7 - 1.1

Zirconium 0.04 - 0.2

Beryllium 0.02 - 0.2 Titanium 0.01 - 0.1

Nickel 0.01 - 0.15

Manganese 0.001 - 0.05

Gallium 0.001 - 0.05

Zinc 0.01 - 0.3 Sodium 0.0005 - 0.001

Aluminum Else

(RF patent W 2180928, IPC 7 C 22 C 21/00, C 22 C 21/16, publication date 2002.03.27 ;. The disadvantage of this alloy, taken as a prototype, is its relatively low manufacturability, high labor input and low yield in the manufacture of semi-finished products and products from it, the inability to obtain thin sheets, thin-walled profiles and stampings from it.

The reasons for the occurrence of the above disadvantages when using the known alloy adopted for the prototype include the fact that the known alloy is characterized by an increased copper content, which negatively affects the heat resistance and ductility during pressure treatment, which leads to increased crack formation, increased rejection by clamps and non-flatness during finishing operations, namely when ironing and dressing semi-finished products, moreover, the high content of sodium and gallium leads to a significant the magnitude of the heat capacity of the alloy, an even greater decrease in its plastic characteristics (A. V Kurdyumov, S.V. Inkin, V. S. Chulkov, G. G. Shadrin., Metallic impurities in aluminum alloys., M.:, Metallurgy. 1988, p. 90.99), which greatly complicates the task of producing suitable ingots and the subsequent preparation of semi-finished products by various types of pressure treatment, as well as high-quality cladding of rolled semi-finished products, due to the formation of significant sections of welded cladding on their surface. Disclosure of invention

The problem to which the invention is directed, is to develop an alloy based on aluminum, intended for the manufacture of semi-finished products and products for aerospace engineering from it, free from the disadvantages of the above and inherent in known technical solutions. The technical result achieved by the implementation of the invention is to obtain an alloy having increased ductility, which will increase its manufacturability, increase the yield in the manufacture of semi-finished products and products, provide the ability to produce thin sheets, thin-walled profiles and stampings while reducing the complexity of production, while maintaining the required strength and operational characteristics of the alloy, as well as semi-finished products and products from it, presented to structural materials la aerospace engineering.

The problem with the achievement of the aforementioned technical result in the implementation of the invention is solved by the fact that the known aluminum-based alloy containing lithium, copper, magnesium, zirconium, beryllium, titanium, nickel, manganese, gallium, zinc, sodium, additionally contains calcium and at least one element selected from the group consisting of vanadium and scandium, in the following ratio, May. %: 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

Titanium 0.01 - 0.1

Nickel 0.01 - 0.15

Manganese 0.01 - 0.2

Gallium up to 0.001 Zinc 0.01 - 0.3

Sodium up to 0.0005

Calcium 0.005 - 0.02 At least one element selected from the group consisting of: Vanadium 0.005 - 0.01

Scandium 0.005 - 0.01

Aluminum Else

The aluminum-based alloy used for the manufacture of semi-finished products and products differs from the prototype both quantitatively (low content of copper, gallium and sodium), and qualitatively

(additionally contains calcium, and at least one element selected from the group consisting of vanadium and scandium).

We found that an increased copper content 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 increased 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.

A decrease in the copper content in the alloy to the limits of 1.3 - 1.5 wt.% Allows it to be almost completely converted into a solid solution, which leads to a significant decrease in the volume fraction of coarse intermetallic compounds of copper-containing phases, which was established by electron microscopic examination of the alloy, and as a result increase the ductility of the alloy. A decrease in the copper content below 1.3 wt.% Will not affect the increase in the ductility characteristics of the alloy, but will significantly reduce its strength characteristics.

In addition, we found that gallium and sodium do not form phases with aluminum and accumulate at the grain boundary, which leads to brittle fracture along the grain boundary during crystallization of the alloy and its processing by pressure.

We found that when the gallium and sodium contents are below 0.001 and 0.0005 wt.%, Respectively, they almost completely dissolve 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 of the alloy, leading to the formation of a more round shape of precipitated intermetallic compounds and their coagulation, which leads to more favorable conditions of shear deformation, and as a result increase the technological plasticity of the alloy.

The introduction of one or more elements from the vanadium, scandium group in the indicated amounts promotes the formation of a homogeneous, fine-grained structure, which enhances the role of zirconium as a modifying additive, providing structural hardening of semi-finished products and alloy products, which allows to achieve the required level of strength properties of the alloy. Various semi-finished products can be made from the proposed aluminum-based alloy: sheets and plates, stampings, extruded products. Various products can be obtained from 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.

An example embodiment of the invention

In industrial conditions, a flat ingot with a cross section of 300x1100 mm was cast from each alloy, the chemical composition of which is shown in Table 1. and round ingots with diameters of 190 mm. and 350 mm.

Alloy W 1 corresponds to the alloy adopted as a prototype, alloys N ⁹ 2,3,4 correspond to the proposed. Melting of the charge, refining and casting of ingots was carried out at a temperature of 710 - 730 ⁰ C. Example 1

Subsequently, clad sheets were made from the flat ingots of each alloy. Sheets were made according to one technological scheme by hot rolling at a temperature of 430 ⁰ C to a thickness of 6.5 mm. rolled up and then after annealing at a temperature of 400 ⁰ C by cold rolling.

It should be noted that the sheet of alloy W 1 managed to be rolled only 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 two cliffs in a roll.

Sheets of alloys N ¹ - 2,3,4 were rolled without breaks to a thickness of 0.5 mm.

Further finishing operations, the laying and dressing of sheets by stretching from N '2,3,4 alloys in comparison with the W 1 alloy, despite their smaller thickness, were more successful and with less rejection at the final inspection for defects: clamps, flatness and cracks. Table 1

The yield for the production of sheets from alloys N '2,3,4 was 30% higher than from alloy E-1.

Subsequently, samples from sheets W 1,2,3,4 were tested under static tension with the determination of tensile strength (σ _c ), yield strength (σo, g) ι relative 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.

From table 2 it can be seen that the proposed alloy is superior to the known alloy (prototype) in terms of ductility while maintaining the required strength characteristics. Example 2

From round ingots with a diameter of 190 mm. profiles of each alloy were made (corners with a shelf thickness of up to 5 mm.).

Profiles from different alloys were made according to one technological scheme by pressing at a temperature of 400 ⁰ C, followed by quenching of the profiles in water, and aging at a temperature of 150 ⁰ C for 24 hours.

The yield for the production of profiles from W 2,3,4 alloys was 15% higher than from W 1 alloy.

Example 3

From round ingots with a diameter of 350 mm. of each alloy were stamped with a wall thickness of 40 mm. table 2

< _* >

Stampings from different alloys were made according to one technological scheme by means of blank stamping at a temperature of 410 ⁰ C, preliminary stamping at a temperature of 410 ⁰ C, and after etching by final stamping at a temperature of 400 ⁰ C, followed by quenching at a temperature of 500 ⁰ C for 2 hours and aging at a temperature of 150 ⁰ C for 24 hours.

Suitable for the production of stampings from alloy N ^! 2,3,4 was 10% higher than N alloy ^! one.

Thus, the proposed alloy ensures the achievement of the goal - improving the ductility of the alloy, and as a result, increasing its manufacturability, increasing the yield in the production of semi-finished products and products from it, making it possible to produce thin sheets, thin-walled profiles and stampings while reducing the complexity of production and maintaining the required strength and performance characteristics of the alloy, as well as semi-finished products and products from it, presented to structural materials for I aerospace engineering.

Claims

CLAIM

1. An aluminum-based alloy containing lithium, copper, magnesium, zirconium, beryllium, titanium, nickel, manganese, gallium, zinc, sodium, characterized in that it additionally contains calcium and at least one element selected from the group including vanadium and scandium, with the following ratio of components, May. %:

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

Titanium 0.01 - 0.1

Nickel 0.01 - 0.15

Manganese 0.01 - 0.2

Gallium up to 0.001 Zinc 0.01 - 0.3

Sodium up to 0.0005

Calcium 0.005 - 0.02

At least one element selected from the group consisting of: Vanadium 0.005 - 0.01

Scandium 0.005 - 0.01

Aluminum Else