Corrosion-resistant alloy based on aluminum, a method of producing semi-finished products and product thereof

 

(57) Abstract:

Corrosion-resistant alloy based on aluminum contains, wt%: Mg of 2.0 to 5.8; Li 1.3 to 2.3; C 0.01 to 0.3; Mn 0,03 - 0,5, Be of 0.0001 to 0.3; at least one metal selected from the group comprising Zr and Sc 0,02 - 0,25 at least one metal selected from the group comprising CA and VA of 0.002 - 0.1; aluminum - rest, the optimal content of zirconium is equal to the ratio, wt. % Zr = 0,08 + 0,07 (2,3 - wt.% Li) to 0.3 (wt.% Sc). A method of producing semi-finished products includes the preparation of the specified alloy, the casting of ingots, homogenization at 400 - 500°C, hot deformation, intermediate annealing at 250 - 450°C, the final deformation, heat treatment in solid solution at 350 - 480°C, quenching at a rate of 0.5 - 3 V_Creteand aging at 100 - 200°C for 0.5 to 36 hours Technical object of the invention is improving the processability during cold deformation and increase corrosion resistance while maintaining a high level of mechanical properties. Stamping after full heat treatment has the following properties at equity and elevation directions, respectively:_B= 440 MPa and 395 MPa;_{of 0.2}= 325 MPa and 300 MPa; = 17% and 10%; = 21% and 15%. The critical voltage at constant load in a corrosive environment in high-rise apavlov, in particular, corrosion-resistant alloy based on aluminum, the method of obtaining the deformed semi-finished products and the product thereof, for use in the aerospace, shipbuilding and automotive industries, where the importance is the weight of the product.

The development of new materials of low density, high strength with high resource characteristics, if possible, making them a wide range of semi-finished products with the use of traditional and progressive technological processes of manufacturing of semi-finished products and products from them is a very important task.

From this point of view, of particular interest are aluminum alloys with lithium and, in particular, the alloys on the basis of the system Al-Li-Mg, which are not only some of the lightest alloys based on aluminum with high rigidity, but also possess a combination of unique properties. First of all it's a good corrosion resistance, ability to be welded all kinds of welding strength of welded joints after welding, equal to 0.7-0.8 from the base material, the ability quenched in air.

Known alloys of this system have drawbacks that prevent acutest for forgings of alloy 1420 is 255 MPa in the longitudinal direction and 235 MPa in a high-rise direction [2]. A method of obtaining, in particular, extruded semi-finished products of alloy 1420 with enhanced mechanical properties. For this primary extrusion ingot is required when the temperature has reached 270-290^oC and subsequent pressing of the intermediate billet at a temperature of 340-350^oC with the stabilization of the speed of expiration [3]. However, pressing large-semis at low temperatures is difficult.

The closest to the proposed alloy is known based alloy of aluminum containing in wt.%:

magnesium - 4,0 - 6,0

lithium - 1,3 - 2,2

copper - 0,005-0,2

beryllium is 0.0001 to 0.3

at least one metal selected from the group comprising zirconium - 0,04-0,12

and scandium - 0,03-0,25

at least one metal selected from the group comprising calcium and barium - 0,002-0,05

aluminum - rest

In the alloy, the presence of impurities, not more than in wt.%:

iron - 0,3

silicon - 0,2

sodium - 0,003 [4]

Alloy can be obtained in various semi-finished products: extruded, rolled and forged. The disadvantage of this alloy is lowered corrosion resistance under constant load in a high-rise direction. In addition, the alloy has to obtain semi-finished products is a well-known method, described in a patent [5]. The method includes the preparation of the alloy, receiving the workpiece, including cast homogenized, deformation at 250-420^oC with the degree of 15-60%, intermediate annealing at 250 - 450^oC, the final deformation degree from 15-60% at 270 - 480^oC, heat treatment for solid solution hardening at a rate of 0.5-3 V_Crete, and aging.

However, the semi-finished products obtained from an alloy 1420 by a known method, have a low resistance to stress corrosion cracking under stress, especially in high-rise direction. Thus, the critical voltage for a constant load in a corrosive environment forgings of alloy 1420 in high-rise direction is not more than 10 kgf/mm².

Products known alloy 1420 produce welded hermetic compartments of the airframe, including fuel tanks [6]. In comparison with the conventional design of watertight compartments, collected from semi-finished products of alloy type D16 (2024) on the mechanical riveting with the use of sealants, welded construction using alloy 1420 has lowered the weight to 24%. It is also known the use of alloy type 1420 as the material for the wheels of the vehicle [7] . However, due to low corru products from well-known alloy exhibit a tendency to embrittlement, significantly reduced elongation and corrosion resistance.

An object of the invention is the development of the base alloy system Al-Mg-Li, method of producing semi-finished products and products with the aim of improving the processability during cold deformation and increase the corrosion resistance while maintaining a high level of mechanical properties.

To achieve this goal based alloy of aluminum containing magnesium, lithium, copper, beryllium, at least one metal selected from the group comprising zirconium and scandium and at least one metal selected from the group comprising calcium and barium, further comprises manganese in the following ratio, wt.%:

magnesium - 2,0-5,8

lithium - 1,3 - 2,3

copper - 0,01 - 0,3

manganese - 0,03 - 0,5

beryllium is 0.0001 to 0.3

at least one metal selected from the group comprising zirconium and scandium - 0,02 - 0,25

at least one metal selected from the group comprising calcium, barium - 0,002-0,1

aluminum - rest

the optimal content of zirconium is equal to the ratio: wt. % Zr = 0,08 + 0,07(2,3 - wt.% Li) to 0.3(wt. % Sc).

The alloy may further contain not more, in wt.%:

Additional introduction of manganese in the presence of zirconium, scandium contributes to the strength due to more uniform distribution of secondary redundant soluble phases in the cross section of the grain, resulting in improved corrosion resistance under stress and plasticity, decrease susceptibility to delayed fracture in high-rise direction. In addition, manganese helps to neutralize the harmful effects of iron, tying it in invoiceline impact is not evident, and when the content is above 0.5% are allocated primary particles insoluble excess phases Al₆Mn, resulting in reduced ductility and processability. The lithium content is selected in the range 1.3 to 2.3% to ensure good weldability, workability and the desired level of mechanical and corrosion properties. At lower lithium less than 1.3% of the reduced modulus of elasticity, yield strength, increases the weight, the alloy loses its ability to thermally prosnetsja. When the content of more than 2.3% deteriorates workability, weldability of the alloy.

Copper in an amount of 0.01 to 0.3% strengthens solid solution of aluminum and entering the eutectic compounds formed by calcium, barium: ( + Al₄Ca(Ba, SR), strengthens the grain boundaries. However, with the introduction of more than 0.3% deteriorates the weldability, increases the critical cooling rate and as a consequence decreases the strength of welded joints. When the content is less than 0.01% of the positive influence of copper is not manifest.

Zirconium and scandium as modifying additives, along with improved weldability provide improved as corrosion and strength properties of the alloy. Optimal zirconium content depends on the content of the lithium iise 0.25% of the allocated primary particles insoluble excess phases Al₃(ScZr), Al₃Zr and Al₃Sc, resulting in reduced ductility.

Calcium and / or barium in these quantities neutralize the harmful effect of sodium, iron and have a modifying effect of crystallization on the grain structure, resulting in improved weldability and increase the yield strength without reducing ductility. When the reduction of calcium, barium below the stated limit of the positive effect not observed. With increasing calcium and barium higher than 0.1% are formed in a significant amount of insoluble particles of excess phases, reducing ductility, especially in high-rise direction. The introduction of beryllium up to 0.3% is sufficient to protect the alloy from oxidation in the process of melting, casting, welding, and when the process heating under deformation and heat treatment. Limiting the content of beryllium in the alloy, it is advisable from the point of view of occupational health.

These calcium, barium, beryllium, and manganese, and copper allow you to use cheaper technology alloy and apply secondary charge involving waste wider range of alloys, including waste of alloys of the system Al-Li-Bars, having a grain size of 300 μm.

This technical result is also achieved by the fact that in the proposed method of producing semi-finished products made of corrosion-resistant alloy based on aluminum, comprising preparing the alloy, the casting of ingots, homogenization, hot deformation, intermediate annealing at 250-450^oC, the final deformation, heat treatment for solid solution hardening at a rate of 0.5-3 V_Creteand aging, prepare a corrosion-resistant alloy based on aluminum, of the following composition in wt.%: magnesium 2,0-5,8; Li 1.3 to 2.3; copper 0.01 to 0.3; manganese 0,03-0,5; beryllium of 0.0001 to 0.3; at least one metal selected from the group comprising zirconium and scandium 0,02-0,25; at least one metal selected from the group comprising calcium and barium of 0.002-0.1; aluminum and impurities - the rest, the optimal content of zirconium is equal to the ratio: [wt.% Zr = 0,08 + 0,07 (2,3 - wt.% Li) to 0.3 (wt. % Sc)], and homogenization is carried out at 400 to 500^oC, heat treatment in solid solution at 350 - 480^oC and aging at 100-200^oC for 0.5 to 36 hours

On mechanical and corrosion properties affects the grain size of the ingot. It is found that with decreasing grain size of the ingot grows mehanicheskii. To ensure the best combination of mechanical and corrosion properties for semi-thickness 15 mm and more preferably using an ingot having a grain size of 60-300 μm, and for semi-finished products thickness less than 15 mm using an ingot having a grain size of 40-200 μm.

In the proposed method, the homogenization of the ingot is carried out at a temperature of 400 to 500^oC, in which eliminates the porosity in the cross section dendritic cell magnesium and lithium and decomposition of the supersaturated solid solution of aluminum with the release of dispersoids of aluminides of zirconium, scandium, manganese. In the case of obtaining forged semi-finished hot deformation is carried out at a temperature 250-470^oC, in at least one stage at a single degree of deformation is not more than 30%, while the total degree of deformation is not more than 70%. Upon receipt of extruded semi-finished hot deformation is carried out at a temperature of 320-420^oC with the degree of deformation of not more than 80%. Hot deformation of rolled semi-finished products is carried out at a temperature of 250-420^oC with a single degree of deformation of not more than 30%, while the total degree of deformation is not more than 95%. To obtain a complex and delicate semi-deformation combination of the measures of the original piece and the geometrical dimensions of prefabricated concrete. The final deformation is carried out in hot or cold.

Between quenching and aging Pets conducting edits with degree no more than 10%.

Mode is selected aging provides the optimum combination of mechanical and corrosion properties.

Of the proposed alloy can be made of various semi-finished products: stamping, forgings, extruded profiles and strip, hot rolled plates, sheets and cold rolled sheets. Products offered alloy manufactured according to the proposed method, can be obtained in various products, for example the blade of the helicopter, the tank, the piping, the wheels of the vehicle, etc. In the proposed product, made of corrosion-resistant alloy based on aluminum, the technical result is achieved by the fact that as the workpiece material used is an alloy based on aluminum, the alloy of the following composition in wt.%: magnesium 2,0 - 5,8; Li 1.3 to 2.3; copper 0.01 to 0.3; manganese 0,03 - 0,5; beryllium of 0.0001 to 0.3; at least one metal selected from the group comprising zirconium and scandium 0,02 - 0,25; at least one metal selected from the group comprising calcium and barium of 0.002-0.1; aluminum - rest, the optimal content Zirconia semi-finished products.

Examples illustrating the proposed invention, is shown below.

In table. 1 shows the chemical composition of the tested compositions are proposed and known alloys.

In the preparation of compositions aluminum, lithium, magnesium, calcium, barium, copper was introduced in pure form, and zirconium, scandium, manganese, and beryllium in the form ligatures.

Example 1

Alloy No. 1 obtained stamping with a wall thickness of 60 mm from the round ingot with a diameter of 450 mm on the following technology: homogenization of the ingot according to the mode - 400^oC, 12 h; deformation (forging) at 250^oC with a total degree of 50% (with a single degree of deformation 15-20%); annealing at 450^oC, 4 h; deformation (forging) at 320^oC with a total degree of 60% (with a single degree of formation 20-25%); annealing at 420^oC, 1 h; deformation (forging) at 320^oC with a total degree of 30%; annealing at 450^oC, 4 h; the final deformation (final pressing) at 400^oC with a total degree of 60%; the heat treatment of the solid solution at 450^oC, quenching with a cooling rate of 1^oC/s, which was 1.5 V_Cretethe aging of the alloy was carried out according to mode 140^oC, 12 h

Example 2

From alloys NN 2, 3 and 4 trains receiving estwenno at 500^oC, 8 h; 450^oC, 12 h and 460^oC, 10 am, the temperature of the pressing 390^oC. the Heat treatment of the solid solution was carried out at 450^oC, followed by quenching with a cooling rate of 1.2^oC/s, which was 1.5 V_Crete; the aging of the alloy was carried out according to mode 130^oC, 16 o'clock

Example 3

From alloys NN 2, 3 and 4 of the compositions of the obtained molded strip cross-section 15 x 60 mm from the pre-olgamorantearevalo at 450^oC, 12 h ingot with a diameter of 70 mm, the temperature of the pressing 390^oC. After annealing at 420^oC, 2 h molded strip laminated with 370^oC to a thickness of 6 mm, this was followed by annealing at 400^oC, 2 h and cold rolling to a thickness of 2.5 mm Heat treatment on the solid solution was carried out at 450^oC, followed by quenching with a cooling rate of 1.2^oC/s on the air under the fan that was 1.5 V_Crete; the aging of the alloy was carried out according to mode 170^oC, 16 o'clock

In table. 2 shows the results of the mechanical and corrosion properties proposed in comparison with the known alloy. The processability of the alloy during cold deformation was estimated by narrowing.

As can be seen from the data table. 2, the proposed alloy is superior invesnicesc properties.

Thus, the alloys of the system Al-Li-Mg low magnesium content by optimizing the content of Zr and Sc with regard to the content of lithium, and the introduction of additional manganese, as well as more accurate way to obtain it is possible to obtain semi-finished products having an improved combination of corrosion resistance, processability with good weldability and low sensitivity to the hub voltage. When the specified content of iron, silicon, zinc, titanium, sodium and copper it is possible to use cheaper technology alloy and apply secondary charge involving waste wider range of alloys, including waste of alloys of the system Al-Li-Cu, Al-Mg-Li-Zn.

The obtained results give reason to recommend the semis of the proposed alloy for products in riveted and welded structures. Application of the proposed alloy will improve the reliability and the life of critical parts and to save weight.

Literature

1. Industrial deformable, sintered and cast aluminum alloys, p/R. F. I. Kvasov and I. N. Fridlender. - M.: metallurgy, S. 217.

2. Technical conditions TL1-92-111-91 "Stamping of aluminum alloy brand 1="ptx2">

5. RF patent N 2048592, MKI C 22 F 1/04, 1994

6. I. N. Fridlyander, A. G. Bratukhin, V. G. Davydov, "Soviet Aluminium-Lithium Alloys of Aerospace Application, Aluminium-Lithium", Papes presentid at the Sixth Int. Al-Li Conf., 1991, G.-Pk(FRG), p.35-42.

7. RF patent N 2051048, MCI 60 In 3/04, 1992

1. Corrosion-resistant alloy based on aluminum containing magnesium, lithium, copper, beryllium, at least one metal selected from the group comprising zirconium, scandium, and at least one metal selected from the group comprising calcium and barium, characterized in that it further contains manganese in the following ratio, wt.%:

Magnesium - 2,0 - 5,8

Lithium - 1,3 - 2,3

Copper - 0,01 - 0,3

Manganese - 0,03 - 0,5

Beryllium is 0.0001 to 0.3

At least one metal selected from the group comprising zirconium and scandium - 0,02 - 0,25

At least one metal selected from the group comprising calcium and barium - 0,002 - 0,1

Aluminum - Rest

the optimal content of zirconium is equal to the ratio: wt.% Zr = 0,08 + 0,07 x (2,3 - wt.% Li) 0,3 x (wt.% Sc).

2. A method of manufacturing semi-finished products made of corrosion-resistant alloy based on aluminum, comprising preparing the alloy, the casting of ingots, homogenization, hot deformation, intermediate annealing at 250 - crit and aging, characterized in that conduct the preparation of the alloy based on aluminum, of the following composition, wt.%: magnesium 2,0 - 5,8; Li 1.3 to 2.3, copper 0.01 to 0.3; manganese 0,03 - 0,5; beryllium of 0.0001 to 0.3; at least one metal selected from the group comprising zirconium and scandium, 0,02 - 0,25; at least one metal selected from the group including calcium and barium, of 0.002 - 0.1; aluminum - rest, the optimal content of zirconium is equal to the ratio: wt.% Zr = 0,08 + 0,07 x (2,3 - wt. % Li) 0,3 x (wt.% Sc), and homogenization is carried out at 400 - 500^oC, heat treatment in solid solution at 350 - 480^oC and aging at 100 - 200^oC for 0.5 to 36 hours

3. The method according to p. 2, characterized in that the semi-thickness of 15 mm and more preferably using an ingot having a grain size of 60 to 300 μm, and for semi-finished products thickness less than 15 mm using an ingot having a grain size of 40 to 200 microns.

4. The method according to p. 2 or 3, characterized in that the hot deformation of forged semi-finished products is carried out at a temperature of 250 - 470^oC, in at least one stage at a single degree of deformation is not more than 30%, while the total degree of deformation is not more than 70%.

5. The method according to p. 2 or 3, characterized in that the hot is it 80%.

6. The method according to p. 2 or 3, characterized in that the hot deformation of rolled semi-finished products is carried out at a temperature of 250 to 420^oC at a single degree of deformation is not more than 30%, while the total degree of deformation is not more than 95%.

7. The method according to any of paragraphs.2 to 6, characterized in that the hot deformation and intermediate annealing carried out repeatedly.

8. The method according to any of paragraphs.2 to 7, characterized in that the final deformation is carried out in hot or cold.

9. The product of corrosion-resistant alloy based on aluminum, characterized in that as the workpiece material used is an alloy of the following composition, wt.%: magnesium 2,0 - 5,8; Li 1.3 to 2.3; copper 0.01 to 0.3; manganese 0,03 - 0,5; beryllium of 0.0001 to 0.3, at least one metal selected from the group comprising zirconium and scandium, 0,02 - 0,25, at least one metal selected from the group including calcium and barium, of 0.002 - 0.1; aluminum - rest, the optimal content of zirconium is equal to the ratio: wt.% Zr = 0,08 + 0,07 x (2,3 - wt.% Li) 0,3 x (wt.% Sc).

10. The product under item 9, characterized in that it is made of hot - or cold-deformed semi-finished products.