High-strength aluminium alloy and method for its obtaining

FIELD: metallurgy.

SUBSTANCE: aluminium-based alloy contains the following, wt %: zinc - 6.35 - 8.0, magnesium - 0.5 - 2.5, copper - 0.8 -1.3, iron - 0.02 - 0.25, silicon - 0.01 - 0.20, zirconium - 0.07 - 0.20, manganese - 0.001 - 0.1, chrome - 0.001 - 0.05, titanium - 0.01 - 0.10, boron - 0.0002 -0.008, beryllium - 0.0001 - 0.05, at least one element from potassium, sodium, calcium group in quantity of 0.0001 - 0.01 each, aluminium is the rest; at total content of zinc, magnesium, copper within 8.5-11.0, and that of zirconium, manganese and chrome - within 0.1-0.35. Method involves loading and melting of charge components, flux treatment of molten metal, molten metal purification, further vacuum treatment of molten metal in mixer and casting of ingots; boron is added to molten metal in the form of Al-Ti-Be alloy which is distributed at least one hour before molten metal pouring to mixer along the whole surface area of mixer bottom; at that, mixer is pre-heated to temperature which is by 15-30°C more than molten metal temperature, and vacuum treatment of molten metal in mixer is performed at temperature of 695-720°C, during 45-90 minutes.

EFFECT: invention allows obtaining high-strength aluminium alloys with absence of primary intermetallic compounds, decreased content in them of non-metallic inclusions and dissolved gases, with stable properties and optimum size of grain on basis of standard furnace and process equipment.

2 cl, 3 tbl

 

The invention relates to the field of metallurgy, in particular to the high-strength alloys of the system Al-Zn-Mg-Cu, designed for the production of extruded, forged and rolled semi-finished products, especially with the massive cross sections used for loaded power parts of aircraft and missiles, cars and trucks, marine and river vessels, agricultural machinery.

The development over the last 25-30 years of aviation, missile, space, and other fields of technology demanded a new, more durable materials, giving the ability to create light and durable designs. One of the main structural materials remained aluminum alloys, but their quality has improved greatly. Their practical application has shown that it is possible to significantly improve the mechanical properties of aluminium alloys, their viscosity, plasticity, resistance to alternating loads, if possible, to reduce the content of impurities, non-metallic inclusions and dissolved gases (hydrogen), to reduce the grain size and to optimize the ratio of the alloying elements in the alloy.

The low density of aluminum alloys promotes the formation of gas pockets and porosity, as the gases can easily penetrate into the metal environment and saturate it. Aluminum is easily oxidized. To clean the melt from the slag and oxides hard is. Slag and oxides remain in the melt in melkorazdroblennym form in suspension, which greatly affects the quality of the alloy. The process of enrichment of the melt of oxide inclusions and hydrogen saturation sharply intensified, if the surface of the tin bath during the melting process is a violation of the integrity of the oxide film. Rational selection of equipment and technological processes, in particular vacuum, consistently guarantee a significant reduction in aluminum alloys impurities, non-metallic inclusions and hydrogen, as well as reducing the size of grain. Known reflective electric furnace (the furnace resistance), which are currently mainly used as mixers. These furnaces to minimize destruction of the oxide film located on the surface of the melt, as well as the lack of turbulent flow on the surface of the tin bath during the melting process, which, in turn, prevents the absorption of hydrogen by the melt and prevents the ingress of separate parts of the oxide film in the melt. Despite their low efficiency furnace resistance, under certain conditions, for example, at the high requirements to the quality of the metal, it is advisable to use as melting units.

The reduction of grain size in aluminum alloys increases the t as technology of the manufacture of aluminum products, and their operational properties. In recent years, an increasingly common practice is the optimal selection of ligatures (modifiers) and technologies for their introduction into the melt to obtain a metal structure with fine equiaxial grains.

Control of the ratio of the alloying elements in the melt allows you to limit the formation of harmful intermetallic compounds in the melt.

The closest analogue, taken as a prototype, is a high-strength alloy based on aluminum (Patent RF №2165995, IPC C22C 21/10, publ. 27.04.2001), of the following composition (wt.%):

Zinc6,35-8,0
Magnesium0,5-2,5
Copperof 0.8-1.3
Iron0,06-0,25
Silicon0,01-0,20
Zirconia0,07-0,20
Manganese0,001-0,1
Chrome0,001-0,05
Titanium0,03-0,10
Berylliumof 0.0001 to 0.05

at least one element from the group of alkaline earth metals:

Potassiumof 0.0001 to 0.01
Sodiumof 0.0001 to 0.01
Calciumof 0.0001 to 0.01
Aluminumrest

This chemical composition of the alloy does not guarantee ingots with optimal grain size and does not take into account the risk of harmful intermetallic compounds at the critical proportions of the alloying elements, limiting technological and mechanical properties of the alloy.

Known methods of smelting, refining, degassing and modification of aluminum alloys (Foundry of non-ferrous and rare metals, Kurdyumov A.V. and others, M.: metallurgy, 1982, s.219-238) prototype.

In these ways are not taken into account the potential for production of high-strength aluminum alloys that allow rational selection of technological processes and standard oven equipment to qualitatively improve consumer properties of the alloys at an acceptable economic cost.

The task to be solved by the invention is the creation of the Plava with improved technological and operational characteristics, and technology, assuring obtaining highly competitive base alloys of the system Al-Zn-Mg-Cu on the type of metallurgical equipment.

The technical result achieved in the implementation of the invention is to develop an alloy with stable properties and optimum grain size, are available for industrial production without excessively complicated equipment or technology, on the basis of a standard furnace and technological equipment, the method guarantees high strength aluminum alloys with lack of primary intermetallics, low content of non-metallic inclusions and dissolved gases (hydrogen).

This technical result is achieved by the fact that high strength-based alloy contains aluminum components in the following ratio, wt.%:

Zinc6,35-8,0
Magnesium0,5-2,5
Copperof 0.8-1.3
Iron0,02-0,25
Silicon0,01-0,20
Zirconia0,07-0,20
Manganese0,001-0,1
Chrome0,001-0,05
Titanium0,01-0,10
Boris 0.0002-0,008

at least one element from the group of alkaline earth metals:

Potassiumof 0.0001 to 0.01
Sodiumof 0.0001 to 0.01
Calciumof 0.0001 to 0.01
Aluminumrest

the alloy further comprises of 0.0001-0.05% beryllium, the amount of main alloying elements (zinc, magnesium, copper) is in the range of 8.5-11.0 per cent, the amount of zirconium, manganese, chromium is in the range of 0.1 to 0.35, and the titanium and boron to form in the alloy fine crystals of titanium diboride.

The technical result is ensured by the method of obtaining high strength aluminum alloy, including loading and melting of the components of the charge in a reverberatory furnace, the refining of the melt flux, subsequent vacuum treatment of the melt in the mixer and casting ingots, melting component of the mixture is carried out in a reflective electric melting pécs is x resistance vacuum treatment of the melt in the mixer is carried out at a temperature 695-720°C for 45-90 minutes, with no less than an hour to the flow of metal in a vacuum mixer over the entire area of the bottom of the mixer is distributed in the ligature of the Al-Ti-B, the mixer is pre-heated at 15-30°C above the temperature of the casting.

The addition of boron, which is introduced into the alloy in the composition of the alloys of the aluminum-titanium-boron (AlTiB), ensures efficient grinding grain aluminum alloys by introducing into the melt of fine crystals of titanium diboride, serve as centers of crystallization. Enter this ligatures leads to the improvement of the mechanical properties and reduce gas porosity.

Alloying elements Zn, Mg, Cu have the greatest influence on the properties of the alloy, and their rational selection largely determines its strength and technological properties. Their total content is less than 8.5% does not guarantee obtaining alloy with stable properties, the total content of alloying elements over 11.5% creates preconditions for the formation of intermetallic compounds such as Al2CuMg (phase S)that adversely affects ductility, crack resistance and fatigue strength.

The presence of zirconium and chromium with simultaneous limitation of manganese (total claimed range 0,1-0,35%) provides the most favorable conditions for the formation and stabilization of the emission of the alloy. Limitation of manganese due to the fact that manganese has a low rate of diffusion in aluminum, which leads to the formation of anomalously supersaturated solid solutions and strong notidentical segregation. Manganese due to the low rate of diffusion leads to the production of large recrystallized grains, the size of which can be reduced by additional doping, in particular the introduction of zirconium and chromium that provide the formation and stabilization of homogeneous structure.

In order to reduce oxidation at elevated temperatures and to improve the fluidity of aluminum alloy additionally legarrette beryllium in amounts of 0.0001 to 0.05%.

The degassing of the melt in the mixer is carried out in the temperature interval from 695°C to 720°C to achieve the greatest effect degassing. This is because the aluminium alloys of the hydrogen bound in the hydrides of the alloying elements with the greatest stability at temperatures 650-690°C. In the temperature range from 695°C to 720°C with intense decomposition of hydrides with hydrogen evolution. The vacuum at temperatures below the lower limit does not provide the desired result. Exceeding the upper limit of the temperature interval above 720°C is not rational because the overheating of the melt lead to growth of grains in the ingot as a result, d is aktivacii modifying particles, that increases the propensity for hot cracking during casting and affects the manufacturability of ingots during the processing pressure.

Before the pumping process in the melt is injected ligatures Al-Ti-B, which is not less than an hour to the flow of metal in a vacuum mixer is placed over the entire area of the bottom of the mixer (the mixer is pre-heated at 15-30°C above the temperature of the casting), which allows the heated ligature will effectively dissolve in the melt.

Introduction ligatures Al-Ti-B at the stage of the technological operation of the vacuum alloy ensures uniform dissolution ligatures while maintaining the effect of grinding grain produced alloy. The effect of grinding grain stored up to 6 hours after entering the ligatures, on the one hand, significantly less time casting ingots, and on the other hand, this time span allows distributed equally alloys in the bulk of the melt.

Industrial applicability of the claimed invention the following examples of specific performance.

For experiments were cast on 3 ingot (prototype and the proposed alloy), table 1 in paragraph 1 given an average chemical composition of the alloy of the prototype, in section 2, we offer alloy.

Table 1
№ p/pChemical composition, wt.%
ZnMgCuFeSiZrMnCrTiBeBKNaCaAl
16,72,021,20,180,080,150,050,030,060,0003-0,0010,0010,003Base
26,32,21,050,120,040,100,040,020,04 is 0.0002is 0.00020,0020,0010,001

The alloys were produced by next technology

1. The calculation of the charge was carried out in accordance with the present invention.

2. Weigh the mixture and submitting it to the oven.

3. Batch charging, melting, alloy preparation, sampling for rapid analysis.

Alloy preparation was carried out:

the prototype in the gas reverberatory furnace;

- the claimed alloy reflective electric melting furnaces of the resistance of the SAN 10.

4. Drain and melt refining.

The refining of the melt processed cryolithogenesis flux was carried out in the foundry ladle.

5. The degassing of the melt.

The degassing of the melt is carried out in a vacuum mixer to reduce the hydrogen content. The degassing of the melt, on average, lasted for 60 minutes at a temperature of 700-720°C. Additionally, in the manufacture of the proposed alloy, an hour before the overflow of the metal in a vacuum mixer over the entire area of the bottom of the mixer, preheated to 15-30°C above the temperature of the casting alloy was uniformly placed ligature Al-Ti-B.

6. The preparation of the molding and casting of ingots.

Casting ingots produced at facilities semi-continuous casting, consisting of a mixer and lita the th machine, in the crystallizers slip.

7. Sampling for chemical analysis.

8. Branding ingots.

9. Weighing cast ingots, slag.

10. The homogenization of the ingot.

The homogenization of the ingot of the alloy is held in the shaft of the electric resistance furnace with forced air circulation.

11. Machining bars.

12. Macro, sampling for determination of hydrogen content and the attenuation of the ultrasonic signal.

13. Then from ingots were produced profiles with thickness of 80 mm

14. The profiles were subjected to a heat treatment according to the following mode: hardening - heating temperature of 470°C, the holding time is 70 minutes, cooling in water; aging two-stage regime 110-120°C, 12 h + 160-170°C for 6 hours.

The mechanical properties and fracture toughness of the alloys was determined on standard samples in the longitudinal (L or PD) and altitude (or VD) directions relative to the fibre direction. Average properties are presented in table 2 (#1 - prototype No. 2 - proposed alloy).

Table 2
№ p/pσin, MPaσin, MPaδ, % Kic, MPa√m
DInDInDInDPLW
152248346842513,64,513870
253150447645215,97,815283

Quality metal ingot and profile is also confirmed by the research results presented in table 3 (No. 1 - prototype No. 2 - proposed alloy).

Table 3
№ p/pHydrogen, cm3/100 gPollution, mm2/cm2From the cylinder. attenuation, dB/cmThe grain size of the ingot, mcm The number of defects DCU profiles PCs/pogon
10,160,0211,856016
20,120,0181,52402

The method is recommended for the production of ingots wrought alloy designations, in particular used in aerospace technology.

1. High-strength aluminum alloy containing zinc, magnesium, copper, iron, silicon, zirconium, manganese, chromium, titanium, boron and at least one element from the group of alkaline earth metals - potassium, sodium, calcium, characterized in that it further contains beryllium in the following ratio, wt.%:

Zinc6,35-8,0
Magnesium0,5-2,5
Copperof 0.8-1.3
Iron0,02-0,25
Silicon0,01-0,20
Zirconia0,07-0,20
Manganese0,001-0,1
Chrome0,001-0,05
Titanium0,01-0,10
Boris 0.0002-0,008
Berylliumof 0.0001 to 0.05

at least one element from the group of alkaline earth metals:
Potassiumof 0.0001 to 0.01
Sodiumof 0.0001 to 0.01
Calciumof 0.0001 to 0.01
AluminumThe rest,

when the total content of major alloying elements zinc, magnesium, copper, 8.5-of 11.0 wt.% and the total content of zirconium, manganese, chromium in the range of 0.1 to 0.35 wt.%, and the titanium and boron are contained in the alloy in the form of fine crystals of titanium diboride.

2. The way to obtain high-strength aluminum alloy, including loading and melting component of the mixture in a reflective electric melting furnaces of the resistance, the introduction of boron in the melt in the form ligatures Al-Ti-B, the melt processing flew the MD, the refining of the melt, the subsequent vacuum treatment of the melt in the mixer and casting ingots, characterized in that the ligature Al-Ti-B injected into the melt before vacuum treatment of the melt in the mixer, and the ligature is not less than an hour before the overflow of the melt in the mixer is placed over the entire area of the bottom of the mixer, which is pre-heated to a temperature of 15-30°C above the melt temperature, and vacuum processing of the melt in the mixer is carried out at a temperature 695-720°C for 45-90 minutes



 

Same patents:

FIELD: metallurgy.

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EFFECT: reduced metal consumption, higher reliability in operation.

2 tbl

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FIELD: metallurgy of metallic materials.

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12 cl, 5 dwg, 7 tbl, 1 ex

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1 tbl

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2 cl, 3 ex

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EFFECT: improved and valuable properties of material.

4 cl, 2 dwg, 2 tbl, 3 ex

FIELD: metallurgy.

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3 tbl, 1 ex

FIELD: metallurgy.

SUBSTANCE: aluminium-based cast alloy has the following chemical composition, in wt %: Cu 3.5-6.0, Mg 0.2-0.9, Ti 0.1-0.4, Zr 0.1-0.5, Mn 0.2-1.2, Zn 0.5-2.5, Sc 0.15-0.5, Al making the rest.

EFFECT: reduced metal consumption, higher reliability in operation.

2 tbl

FIELD: metallurgy.

SUBSTANCE: invention relates to alloy of AA7000 series and to the manufacturing method of products from this aluminium alloy, and namely to aluminium deformed products of relatively large thickness, namely of 30 to 300 mm. Method involves casting of workpiece - ingot of aluminium alloy of AA7000 series, which contains >0.12 to 0.35% Si, pre-heating and/or homogenisation of workpiece, hot deformation treatment of workpiece using one or more methods chosen from the group, which involves rolling, extrusion and forging, optionally cold deformation treatment, solution treatment, workpiece solution treatment cooling, optional tension or compression or other cold deformation treatment for release of stresses, which is performed by straightening or drawing or by cold rolling, ageing of workpiece in order to achieve the required state. At least one heat treatment is performed at temperature in the range of more than 500°C, but lower than solidus temperature of the considered aluminium alloy. The above heat treatment is performed either: (i) after heat treatment by homogenisation prior to hot deformation treatment, or (ii) after solution treatment, or (iii) both after heat treatment by homogenisation prior to hot deformation treatment, and after solution treatment.

EFFECT: obtaining the product from deformed aluminium alloy, which has improved balance of properties, and namely destruction viscosity, tensile yield point, tensile ultimate strength and relative elongation.

30 cl, 8 tbl, 3 ex

FIELD: metallurgy.

SUBSTANCE: group of inventions can be used at manufacture of semi-finished products in the form of forgings, formings, pressed rods and channels, rolled plates and sheets from high-strength alloys of Al-Zn-Mg-Cu system, which are intended to be used in power structures of aerospace equipment and transport means, on which stringent strength, crack resistance, fatigue life, corrosion resistance requirements are imposed. In order to solve the set task, high-strength alloy on the basis of aluminium, which contains the following, wt %, is proposed: Zn 6.2-8.0, Mg 1.5-2.5, Cu 0.8-1.2, Zr 0.05-0.15, Fe 0.03-0.15, Ti 0.01-0.06, at least one element of the group of metals: Ag 0.01-0.5, Sc 0.01-0.35, Ca 0.0001-0.01, Al and inevitable impurities are the rest. In particular version of alloy the inevitable impurities include not more than 0.05 of Si, Mn, Cr, Ni and not more than 0.01 of Na, H2, O2, B, P. Method for obtaining an item from this alloy involves ingot casting, its homogenisation, hot deformation and strengthening heat treatment of the item, which includes hardening and staged ageing; at that, during the ingot casting there performed is melt purification by blowing with argon or mixture of argon with chlorine and out-of-furnace purification using rotor and/or filtering devices, and homogenisation is performed as per one-stage mode at temperature which is by 55-130°C lower than unbalanced solidus (tu.s.) temperature of this alloy with exposure during 8-36 h or as per two-stage mode at temperature at the first stage at the temperature which is by 175-280°C lower than tu.s. temperature, and at the second stage at the temperature which is by 75-125°C lower than tu.s., with exposure at each stage to 24-36 h; hot deformation is performed at temperature of 300-420°C, hardening is performed at temperature which is by 50-120°C lower than tu.s. during the time determined with the item thickness, with further cooling to temperature of not more than 80°C.

EFFECT: improving the set of mechanical and corrosive characteristics, and characteristics of crack resistance, life time and manufacturability.

10 cl, 1 tbl

FIELD: metallurgy.

SUBSTANCE: invention refers to alloys on base of aluminium, particularly to Al-Zn-Cu-Mg alloys on base of aluminium, and also to procedure of fabrication of rolled or forged deformed product of it and to rolled or forged deformed product proper. The procedure consists in following stages: a) casting an ingot, containing wt % Zn 6.6-7.0, Mg 1.68-1.8, Cu 1.7-2.0, Fe 0-0.13, Si 0-0.10, Ti 0-0.06, Zr 0.06-0.13, Cr 0-0.04, Mn 0-0.04, additives and other side elements ≤0.05 each, b) homogenising of the said ingot at 860-930°F or, preferably, at 875-905°F, c) hot deformation treatment of the said ingot with temperature at input 640-825°F, but preferably - 650-805°F by rolling or forging to a plate with finish thickness from 2 to 10 inches, d) thermal treatment for solid solution and quenching the said plate, e) drawing the said plate with residual deformation from 1 to 4 %, f) ageing the said plate by heating at 230-250°F during from 5 to 12 hours and 300-360°F during from 5 to 30 hours during equivalent time t(eq) between 31 and 56 hours. Equivalent time t(eq) is determined from formula:

where T corresponds to instant temperature in K during annealing, while Tcontr corresponds to control temperature equal to 302°F (423K), and t(eq) is expressed in hours.

EFFECT: production of deformed product possessing improved combination of mechanical strength for corresponding level of crack resistance and resistance to corrosion cracking under load.

8 cl, 2 dwg, 10 tbl, 4 ex

FIELD: metallurgy.

SUBSTANCE: alloy on base of aluminium contains following components wt %: zinc 5-8, magnesium 2-3.1, nickel 1-4.2, iron 0.02-1, zirconium 0.02-0.25 %, copper 0.05-0.3 %. Also, temperature of equilibrium solidus of material is as high as 550°C and hardness is as high as 180 HV. Alloy has a structure corresponding to matrix formed with solid solution of aluminium with uniformly distributed disperse particles of secondary discharges in it and particles of aluminides containing nickel and iron of eutectic origin uniformly distributed in matrix. Also, alloy contains matrix and aluminides at the following ratio, vol % aluminides containing nickel and iron 5.0-6.3, matrix - the rest.

EFFECT: production of new high-strength alloy thermally hardenable and designed both for fabrication of shaped casting and of deformed semi-products.

4 cl, 5 tbl, 4 ex

FIELD: metallurgy.

SUBSTANCE: product consists of following components, wt %: Zn 9.0-14.0, Mg 1.0-5.0, Cu 0.03-0.25, Fe <0.30, Si <0.25, Zr from 0.04 to less, than 0.3 and one or more elements chosen from group consisting of: Ti <0.30, Hf <0.30, Mn <0.80, Cr <0.40, V <0.40 and Sc <0.70, random elements and impurities, each <0.05, totally <0.15, and aluminium - the rest. The procedure for fabrication of product out of aluminium alloy consists in casting an ingot, in homogenisation and/or in preliminary heating the ingot upon casting, in hot treatment of the ingot into preliminary finished product with one or more methods, chosen from the group including rolling, extrusion and forging. Not necessarily, the preliminary treated product can be heated or hot treated and/or cold treated to a required shape of a blank; further formed blank is subjected to heat treatment to solid solution, to hardening blank heat treated to solid solution; not necessarily, hardened blank can be stretched or compressed, or cold treated by other way to stress relief, for example, by levelling sheet products or artificial ageing, till obtaining a required condition.

EFFECT: product with reduced tendency to forming hot cracks and with improved characteristics of strength, fracture toughness and hardness over 180 HB at artificially aged state.

32 cl, 6 tbl, 6 ex

FIELD: metallurgy.

SUBSTANCE: invention refers to deformed alloys of aluminium-zinc-magnesium-scandium system and to procedure for their production. Aluminium alloy contains from 0.5 to 10 wt % Zn, from 0.1 to 10 wt % Mg, from 0.01 to 2 wt % Sc, at least 0.01 wt % at least one alloying additive chosen from Ag at amount of up to 1 wt % and Sn at amount of up to 0.5 wt %, aluminium and unavoidable additives - the rest. The procedure consists in production of the said aluminium alloy, in homogenisation, in extrusion, in treatment for solid solution, in quenching, in straightening with drawing and in ageing.

EFFECT: alloys possess good qualities such as relatively high strength and excellent corrosion resistance.

33 cl, 3 dwg, 4 tbl

FIELD: metallurgy.

SUBSTANCE: method involves ingot casting with the following composition, wt %: Zn 6.0 - 11.0, Cu 1.4 - 2.2, Mg 1.4 - 2.4, Zr 0.05 - 0.15, Ti <0.05, Hf and/or V <0.25, optionally Sc and/or Ce 0.05 - 0.25%, optionally Mn 0.05 0.12%, and inevitable impurities and aluminium is the rest, homogenisation and/or pre-heating of ingot after casting, hot deformation processing of ingot so that pre-processed product is obtained, heating of pre-processed product and either hot rolling of heated product to final thickness, or hot rolling and cold rolling of heated product to final thickness, heat treatment for solid solution and hardening of heat-treated product for solid solution, optional tension or compression of hardened product and optional ageing of hardened and optionally tensed or compressed product to the desired state; at that, rolled product at its final state has in fact fully non-recrystallised microstructure at least in position T/10.

EFFECT: product has increased yield point at compression and high specific energy of crack propagation, and improved viscosity and corrosion resistance properties.

21 cl, 6 tbl, 3 ex

FIELD: metallurgy.

SUBSTANCE: aluminium-based alloy contains the following, wt %: zinc 0.5-0.7; titanium 0.1-0.13; silver 1.1-1.3; nickel 0.25-0.5; copper 0.15-0.25; cobalt 0.7-0.9; aluminium - the rest.

EFFECT: alloy is characterised with increased strength.

1 tbl, 3 ex

FIELD: metallurgy.

SUBSTANCE: Invention relates to metallurgy and may be sued in producing strained semi-finished products from thermally non-hardenable welded aluminium-based alloys used as structural and semiconductor material, primarily, in aerospace and nuclear engineering. Aluminium-base alloy comprises the following components in wt %: magnesium - 1.8-2.4, scandium - 0.2-0.4, zirconium - 0,1-0.2, cerium - 0.0001-0.005, iron - 0.01-0.15, silicon - 0.01-0.1, aluminium making the rest. Note here that iron-to-silicon content ratio may not be less than unity.

EFFECT: higher strength and conductivity, hence, reduced weight.

2 tbl, 1 ex

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