WO2017078558A1

WO2017078558A1 - Superplastic aluminium alloy (variants), use thereof and product made therefrom

Info

Publication number: WO2017078558A1
Application number: PCT/RU2015/000731
Authority: WO
Inventors: Anastasia Vladimirovna MIKHAYLOVSKAYA; Anton Dmitrievich KOTOV; Vladimir Kimovich PORTNOY; Anna Alekseevna KISHCHIK; Mikhail Sergeevich KISHCHIK
Original assignee: Autonomous Non-Profit Organization For Higher Education "Skolkovo Institute Of Science And Technology"
Priority date: 2015-11-02
Filing date: 2015-11-02
Publication date: 2017-05-11
Also published as: EA033989B9; EA033989B1; EA201891097A1

Abstract

The present disclosure relates to a superplastic aluminium alloy useful in manufacturing semi-products and articles of manufacture by superplastic forming. The superplastic aluminium alloy disclosed comprises 3.3 to 5.9 wt% magnesium, 0.6 to 1.2 wt% nickel, 0.4 to 1.2 wt% iron, 0.12 to 0.35 wt% zirconium, 0.03 to 0.4 wt% chromium, 0.03 to 0.9 wt% manganese, the balance being aluminium and unavoidable impurities. In one embodiment, the alloy further comprises up to 0.5 wt% scandium. Sheets made of the alloy according to the present disclosure exhibit high-speed superplasticity at the temperatures of 490-540 °C, i.e. elongation to fracture of at least 400% at the strain rate of 10^-2 s^-1 while maintaining strength properties at least comparable, or even superior to those of conventional superplastic Al-Mg alloys. The present disclosure further relates to a use of the superplastic alloy for making products by superplastic forming and to a product made from such alloy.

Description

SUPERPLASTIC ALUMINIUM ALLOY (VARIANTS), USE THEREOF AND PRODUCT MADE

THEREFROM

Technical field

The present disclosure relates to the field of physical metallurgy and material processing technologies. More particularly, the disclosure relates to superplastic aluminium-based alloys with magnesium (Mg) as the next major constituent, which alloys have micrograin structure and are useful in manufacturing high-performance materials, semi-products and articles of manufacture by superplastic forming, for applications in various industries, including automotive, aerospace industry, shipbuilding and others.

Background art

Superplastic alloys are crystalline metals which are capable of being stretched to several times their original size without failure during tensile deformation at elevated temperatures. Superplastic alloys elongate and become thinner in a uniform manner when drawn under tension rather than forming a "neck" (i.e. a local narrowing) which leads to fracture. Such metals usually have a fine grain crystalline structure, typically with the average particle size of less than 10 μιη or even less, allowing the grain boundary sliding effect and thereby, the superplastic deformation. Such alloys are used in the industry already for several decades, especially in automobile, aircraft, aerospace and shipbuilding industries.

Superplastic aluminium alloys generally contain significant amounts of alloying elements with the most common ones being magnesium, zinc, copper and lithium. Typical examples of commercial alloys include AA2004 (Supral 100), high-strength aluminium alloy 7475 and Al-Mg alloys of the AA5000 series. Among the latter, one of the most popular commercial alloys is AA5083 (AI-4.7Mg-0.86Mn-0.04Cu-0.09Si-0.21 Fe-0.05Zn) which exhibits 300-350% elongation at 520-540°C and a strain rate of 10^"3 s^"1 which is considered to be optimal strain rate for this alloy. Such a strain rate, however, is not high enough to allow high-speed superplastic forming which would be desirable in industry. Thus, at strain rates of 10^"4-10^"3 s^"1 optimal for the majority of conventional Al-Mg alloys, shaping a small part of an average complexity takes from 20 to 60 min and more.

Therefore, numerous attempts have been made to create a superplastic Al-Mg alloy, which would be capable of high-speed superplastic forming without sacrificing elongation and strength properties. One of the alloys developed, Alnovi-1 (AI-4.5Mg-0.7Mn-0.12Cr-<0.1 Fe- <0.1 Si), produced by the Furukawa-Sky Aluminum Corp. (JP) is formable at 10 * s^"1 while having elongation of 250% at this strain rate. A modification of this alloy, Alnovi-U (AI-4.75Mg-1.42Mn- 0.05Fe-0.03Si) by the Furukawa-Sky Aluminum Corp., shows elongation of 300% at 10^"2 s^"1 strain rate at 470°C. Further research in the art has been focused on modifying Al-Mg-Mn alloy matrix with various alloying elements such as zinc, copper, iron, chromium, titanium or zirconium, preferably with cheaper ones. In particular, EP 0297035 discloses a superplastic aluminum alloy comprising 4.54 wt% Mg, 1 .2 wt% Fe, 0.24 wt% Mn, 0.15 wt% Zr, 0.10 wt% Si and 0.03 wt% Ti. When tested at 0.5x 10^"3 s^"1 strain rate at 490 °C, the alloy exhibited the elongation of 550-585%, however elongation at higher strain rates was not evaluated.

The Japanese patent application No. 63G 107815 filed by Kobe Steel LTD describes a superplastic aluminium alloy comprising 2-5 wt% Mg, 0.5-3.0 wt% Fe and one or more elements selected from 0.05-1 .5 wt% Mn, 0.05-0.5 wt% Cr, 0.05-0.5 wt% Zr, 0.05-0.5 wt% Va and <0.15% Ti. The alloy exhibits the elongation of 500-650% when tested at 0.5x 10^"3 s^"1 strain rate at 500 °C; elongation at higher strain rates was not evaluated.

Another approach was used in US 5,405,462 disclosing thermally treated powder compositions containing aluminium as a base element and a variety of alloying elements, including, in different combinations, Fe, Ni, Mn, Cr, Zr, Zn, Ti, Si, V, misch metals and others. The tested alloys showed immensely good high-speed superplastic properties (e.g. the elongation of 360-1060% at the strain rate of 10° s^"1 at 550 °C). However, the process of preparing the alloy is so complex, costly and time-consuming, that it can be hardly ever adapted to an industrial scale production.

Therefore, there still remains a need in a superplastic aluminium alloy, which would be capable of high-speed superplastic deformation while maintaining good elongation and strength properties. This and other needs are addressed in the present disclosure as described in more details below.

Summary of the invention

The present disclosure provides a superplastic aluminium alloy capable of good superplastic elongation at a strain rate up to 10^"' s^'1 while exhibiting strength properties at least comparable, or even superior to those of conventional superplastic Al-Mg alloys.

In one aspect, the present disclosure relates to a superplastic aluminium alloy comprising magnesium, nickel, iron, zirconium, chromium and manganese in the following amounts, wt %:

Magnesium 3.3 to 5.9

Nickel 0.6 to 1 .2

Iron 0.4 to 1 .2

Zirconium 0.12 to 0.35

Chromium 0.03 to 0.4

Manganese 0.03 to 0.9

aluminium and unavoidable impurities the balance. As was unexpectedly found by the present inventors, such a composition of the alloy results in superior high-speed superplastic deformation (SPD) properties. Without wishing to be bound by any specific theory, the inventors of the present invention suppose that the superior properties are achieved at least partly due to the formation of a specific micro/nano-grain alloy structure, where micro-particles and nano-particles are dispersed in aluminium matrix. This specific structure of the inventive alloy is characterized by the presence of both coarse near globular particles of AI₉FeNi having average particle size of about 1 to 2 μηη and volume percentage of about 4 to 8 vol%, and finely dispersed AI₆( n,Cr) and AI₃Zr particles having average particle size of less than about 100 nm and volume percentage of about 0.3 to 6 vol%. The coarse particles of the AlgFeNi phase provide particle stimulated nucleation during recrystallisation. Thereby, due to increased dislocations concentration being created during deformation on local spots near coarse particles, the particles promote nucleation of new grains thereby providing the formation of a more finely dispersed grain structure. The dispersed particles effectively stabilize recrystallized grain at high temperatures. Besides, in particular embodiments, at the zirconium content of about 0.12-0.35 wt%, AI₃Zr particles suppress static recrystallization thereby providing finer grains during SPD.

It shall be appreciated that in the present disclosure, the term "alloy" will be used interchangeable with the term "alloy material", and accordingly, the term "superplastic alloy" will be used interchangeable with the term "superplastic alloy material".

In particular embodiments of the invention, the disclosed alloy materials exhibit at least one of the following characteristics, as measured at the room temperature: yield strength from about 160 to about 250 MPa, tensile strength from about οτ 300 to 360 MPa, and at the strain rate of 10^"2 s^"1 and the temperature of 490-540 °C, the alloy exhibits elongation of at least 430%.

In some embodiments, the alloys according to the invention further comprise one or more additional components selected from transition metals, which are also called D-block elements, wherein the total amount of the additional component(s) is up to 0.4 wt%. The D- Block elements have their d-orbital filled with the electronic shell "n-1 " and are found in groups 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , and 12 of the periodic table.

According to some preferable embodiments of the invention, the transition metal or the d block element is scandium, and the alloy has at least one of the following characteristics, as measured at the room temperature: yield strength of about 255 MPa, tensile strength of about 370 MPa, and at the strain rate of 10^"2 s^"1 and the temperature of 480-500°C, the alloy exhibits elongation of 520%.

In a further aspect, the present disclosure relates to a high-performance alloy material made of the claimed superplastic aluminium alloy.

In a particular embodiment, the alloy material can be produced in the form of a sheet product. In a further embodiment, the thickness of the sheet product is from about 0.01 to about 20 mm. in some embodiments, the alloy material can be also shaped at the final processing step to produce alloy plate, wire, bars, or products of any other shape with specific mechanical properties.

According to still another aspect, the present disclosure relates to the use of the inventive superplastic alloy material for producing various products by superplastic forming.

Brief description of the drawings

Fig. 1 represents a scanning electron microscopy (SEM) image showing the structure of an illustrative alloy according to the invention: Alloy No.1 (AI-4.5Mg-1.0Ni-1.0Fe-0.25Zr-0.05Mn- 0.05Cr), grain size = 5.5±0.3 μηι.

Fig. 2 represents a SEM image showing the structure of another illustrative alloy according to the invention: Alloy No.2 (AI-4.8Mg-0.9Ni-0.9Fe-0.3Zr-0.05Mn-0.05Cr), grain size = 5.0±0.2 μιτι.

Fig. 3 represents a SEM image showing the structure of a yet another illustrative alloy according to the invention: Alloy No.3 (AI-5.3Mg-1 .0Ni-0.6Fe-0.15Zr-0.6Mn-0.15Cr), grain size = 4.8±0.2 Mm.

Fig. 4 represents a photograph of the two sheets made of the aluminium Alloy No.1 according to the present invention after performing the formability test (cone-cup testing method).

Fig. 5A represents a graph showing gas pressure as function of time in the cone-cup test.

Fig. 5B is a photograph of the cone formed in the cone-cup test, where it is shown how the cone height and the thickness of the cone were measured.

Detailed description of the invention

The present disclosure provides a superplastic aluminium alloy having excellent superplastic properties at strain rates up to 10^"1 s^"1 while exhibiting strength properties at least comparable, or even superior to those of conventional superplastic Al-Mg alloys.

In one aspect, the present disclosure relates to a superplastic aluminium alloy comprising magnesium, nickel, iron, zirconium, chromium and manganese in the following amounts, wt%:

magnesium 3.3 to 5.9

nickel 0.6 to 1.2

iron 0.4 to 1.2

zirconium 0.12 to 0.35

chromium 0.03 to 0.4

manganese 0.03 to 0.9 aluminium and unavoidable impurities the balance.

In a particular embodiment, the unavoidable impurities are selected from the group consisting of silicon, titanium, zinc and copper, and their respective amounts, wt%, are as follows:

silicon below 0.16

titanium below 0.1

zinc below 0.1

copper below 0.1 .

In a preferred embodiment, the total amount of unavoidable impurities is not more than 0.3 wt%.

The alloy material exhibits at least one of the following properties, as measured at the room temperature: yield strength from about 190 to about 230 MPa, tensile strength from about OT 320 to 330 MPa. At the strain rate of 10^"2 s^'1 and the temperature of 490-540 °C, the alloy material exhibits elongation of at least 400%.

In some embodiments, the proposed superplastic aluminium alloy comprises magnesium, nickel, iron, zirconium, chromium and manganese in the following amounts, wt %:

magnesium 3.9 to 5.3

nickel 0.6 to 1.0

iron 0.6 to 1.0

zirconium 0.1 to 0.3

chromium 0.05 to 0.28

manganese 0.05 to 0.75

aluminium and unavoidable impurities the balance.

In a more specific embodiment, the amounts of the alloy components are as follows, wt%:

magnesium 4.8

nickel 1.0

iron 0.9

zirconium 0.25

chromium 0.05

manganese 0.05

aluminium and unavoidable impurities the balance. In some embodiments, the alloy further comprises one or more additional components selected from transition metals or d-block elements, wherein the total amount of the additional component(s) is up to 0.4 wt%.

According to one of the preferable embodiments of the invention, the transition metal or the d-block element is scandium, and the alloy has at least one of the following characteristics, as measured at the room temperature:

yield strength of about 255 MPa, and

tensile strength of about 370 MPa.

At the strain rate of 10^"2 s^"1 and the temperature of 480-500 °C, the alloy exhibits elongation of about 520%. Remarkably, these properties remain substantially the same after performing the general corrosion test in accordance with ASTM G1 10-92 standard.

The structure of the alloy according to the invention is composed of micro- and nano- particles dispersed in aluminium matrix.

In particular, in one embodiment, the alloy is characterized by the presence of near spherical AI₉FeNi particles having average particle size from about 1 to about 2 μηι, the volume fraction thereof being from about 2 to about 10 vol%, preferably from about 4 to about 8 vol%; and finely dispersed AI₆(Mn,Cr) and AI₃Zr particles having average particle size of below about 100 nm, the volume fraction thereof being from about 0.1 to about 8 vol.%, preferably from about 0.3 to about 6 vol%.

In a further aspect, the present disclosure relates to a product made of the claimed superplastic aluminium alloy material. In a particular embodiment, the product is in the form of a sheet material. In a further embodiment, the thickness of the sheet material is from about 0.01 mm to about 20 mm. In a still further embodiment, the thickness of the sheet material is from about 0.1 mm to about 10 mm. In one of the preferable embodiments, the thickness of the sheet material is from about 1 mm to about 2 mm.

According to another aspect, the present disclosure relates to a use of the claimed superplastic alloy material for producing a product by superplastic forming.

In one embodiment, the product is a vehicle component. In a particular embodiment, the vehicle component is an interior or exterior body panel. In one embodiment, the vehicle is a motor vehicle. In another embodiment, the vehicle is an aircraft. In a further embodiment, the vehicle is a spacecraft.

In still another embodiment, the product is a household appliances component. In another embodiment, the product is a construction element. In a particular embodiment, the construction element has a honeycomb structure. In a still further embodiment, the product is a tool. In another embodiment, the product is a box. The invention is further illustrated by the following non-limiting examples.

Experimental examples

A product made of the alloys according to the present invention was prepared in the form of sheets having thickness of 1 -2 mm, according to the following procedure:

1. Ingots were prepared in a water-cooled copper mold, wherein the cooling rate was set to about 15 K/s;

2. Homogenization annealing was carried out at the temperature of not more than 550 ^<€;

3. Hot rolling was performed, wherein the sheets were deformed by 50 to 70%;

4. Cold rolling was carried out to obtain 1 mm to 2 mm thickness sheets (50 to 80% deformation).

An average size of recrystallized grains upon heating of the cold-rolled sheets to superplastic deformation temperature of 550 °C was 5.0±0.3 μηη.

Table 1 below illustrates the composition of four illustrative alloys according to the present invention (Alloys 1 to 4). The structures of the Alloys 1 to 3 are shown in Figs. 1 to 3, respectively.

Table 1 - Chemical composition of the Alloys 1 to 4 (EDS analysis).

Alloy No.1

The chemical composition of the Alloy No. 1 is as shown in Table 1 . Sheets made of the alloy were prepared according to the procedure as described above. The final sheet thickness was 1 .2 mm.

An average size of recrystallized grains upon heating of the cold-rolled sheets to superplastic deformation temperature of 490 °C was 5.5±0.3 μηη.

Superplastic properties of the Alloy No.1 :

• At the strain rate of 5x10^"3 s^'1 and the temperature of 490 °C, the elongation was 540 % and the flow stress value was 11 MPa; • At the strain rate of 1 x10^~2 s^"1 and the temperature of 490 °C, the elongation was 440 % and the flow stress value was 15 MPa;

• At the strain rate of 1 x10^"1 s^"1 and the temperature of 490 °C, the elongation was 300 % and the flow stress value was 35 MPa.

Mechanical properties of the Alloy No.1 measured at the room temperature were as follows:

• The yield strength being 220 MPa;

• The tensile strength being 330 MPa; and

• The elongation being 15 %.

Alloy No.2

The chemical composition of the Alloy No. 2 is as shown in Table 1. Sheets made of the alloy were prepared according to the procedure as described above. The final sheet thickness was 1.2 mm.

An average size of recrystallized grains upon heating of the cold-rolled sheets to superplastic deformation temperature of 490 °C was 5.0±0.2 μνη.

Superplastic properties of the Alloy No.2:

• At the strain rate of 5x10^~3 s^"1 and the temperature of 490 °C, the elongation was 380 % and the flow stress value was 15 MPa;

• At the strain rate of 1 x10^~2 s^"1 and the temperature of 490 °C, the elongation was 330 % and the flow stress value was 19 MPa.

Mechanical properties of the Alloy No.2 measured at the room temperature were as follows:

• The yield strength being 190 MPa;

• The tensile strength being 300 MPa; and

• The elongation being 18 %.

Alloy No.3

The chemical composition of the Alloy No. 3 is as shown in Table 1 . Sheets made of the alloy were prepared according to the procedure as described above. The final sheet thickness was 1 .2 mm.

An average size of recrystallized grains upon heating of the cold-rolled sheets to superplastic deformation temperature of 550 °C was 4.810.2 μηη.

Superplastic properties of the Alloy No.3: • At the strain rate of 5x 1 0^"3 s^~1 and the temperature of 540 °C, the elongation was 520 % and the flow stress value was 9.7 MPa;

• At the strain rate of 1 x1 0^"2 s^"1 and the temperature of 540 °C, the elongation was 400 % and the flow stress value was 12 MPa.

Mechanical properties of the Alloy No.3 measured at the room temperature were as follows:

• The yield strength being 200 MPa;

• The tensile strength being 330 MPa; and

• The elongation being 1 6 %.

Alloy No.4

The chemical composition of the Alloy No. 4 is as shown in Table 1. Sheets made of the alloy were prepared according to the procedure as described above. The final sheet thickness was 2 mm.

The grain structure remains non-recrystallized upon heating of the cold-rolled sheets to superplastic deformation temperature of 500 °C.

Superplastic properties of the Alloy No.4:

• At the strain rate of 5x 1 0^"3 s^"1 and the temperature of 500 °C, the elongation was 600 % and the flow stress value was 9.0 MPa;

• At the strain rate of 1 x 1 0^"2 s^~1 and the temperature of 480 °C, the elongation was 520 % and the flow stress value was 14.0 MPa.

Mechanical properties of the Alloy No.4 measured at the room temperature were as follows:

• The yield strength being 255 MPa;

• The tensile strength being 370 MPa; and

• The elongation being 1 6 %.

Alloy No.5

The chemical composition of the Alloy No. 5 is as shown in Table 1. Sheets made of the alloy were prepared according to the procedure as described above. The final sheet thickness was 1 .2 mm.

An average size of recrystallized grains upon heating of the cold-rolled sheets to superplastic deformation temperature of 540 °C was 5.5±0.2 μητι. Superplastic properties of the Alloy No.5:

• At the strain rate of 5x 10^"3 s^~1 and the temperature of 540 °C, the elongation was 520 % and the flow stress value was 8.0 MPa;

• At the strain rate of 1 x 10^"2 s^"1 and the temperature of 540 °C, the elongation was 450 % and the flow stress value was 1 1 .0 MPa.

Mechanical properties of the Alloy No.5 measured at the room temperature were as follows:

• The yield strength being 220 MPa;

• The tensile strength being 340 MPa; and

• The elongation being 15 %.

As can be seen from the above experimental data, the alloys according to the present invention exhibit excellent elongation and strength properties at the strain rate of 10^"2 s^"1. Moreover, even at the strain rate of 10^"1 s^"1, the Alloy No.1 exhibited 300% elongation, which is comparable to the elongation of conventional alloys at 1 0^~3 s^" , i.e. at the strain rate 100 times lower.

Formability testing

Formability of the alloy according to the invention was measured using the cone-cup testing method.

Two samples (Sample No.1 and Sample No.2 in Table 2) made of the Alloy No. 1 were prepared in the form of two individual sheets, each having the size of 150x 150x 1 .2mm. Three samples made of AA5083 were used as reference samples.

The testing results are shown in Table 2 below.

Table 2. Formability testing results

As can be seen from the testing results in Table 2, the alloy according to the present invention exhibits superior formability properties as compared to the conventional alloy AA5083.

Table 3 below provides further comparison between the disclosed alloy and the conventional alloy AA5083.

Table 3. Characteristics of the alloy according to the invention vs AA5083 alloy

^* - Optimal strain rate

As follows from the comparative data in Table 3, the properties of the presently disclosed alloy at 10^'1 s^" are comparable to those of the conventional alloy at 1 10³ s^' Thus, the claimed alloy can undergo superplastic forming at the strain rate 100 times higher as compared to the conventional alloy while maintaining good superplastic and mechanical properties, thereby allowing to reduce significantly the duration of a superplastic forming process and as a result, reduce the costs of the alloy production.

Having thus described the invention in rather full detail, it will be understood that these details need not be strictly adhered to but that various changes and modifications may suggest themselves to one skilled in the art, all falling within the scope of the invention as defined by the appended claims.

Claims

WE CLAIM:

1. A superplastic aluminium alloy comprising magnesium, nickel, iron, zirconium, chromium and manganese in the following amounts, wt %:

Magnesium 3.3 to 5.9

Nickel 0.6 to 1.2

Iron 0.4 to 1.2

zirconium 0.12 to 0.35

chromium 0.03 to 0.4

manganese 0.03 to 0.9

aluminium and unavoidable impurities the balance.

2. The proposed superplastic aluminium alloy of claim 1 , comprising magnesium, nickel, iron, zirconium, chromium and manganese in the following amounts, wt %:

magnesium 3.9 to 5.3

nickel 0.6 to 1.0

iron 0.6 to 1.0

zirconium 0.1 to 0.3

chromium 0.05 to 0.28

manganese 0.05 to 0.75

aluminium and unavoidable impurities the balance.

3. The superplastic aluminium alloy of claim 1 or 2, wherein the unavoidable impurities are selected from the group consisting of silicon, titanium, zinc and copper, and their respective amounts, wt%, are as follows:

silicon below 0.16

titanium below 0.1

zinc below 0.1

copper below 0.1.

4. The superplastic aluminium alloy of claims 1-3, wherein the total amount of unavoidable impurities is not more than 0.36 wt%, preferably, not more than 0.3 wt%.

5. The superplastic aluminium alloy according to any one of claims 1 to 4, wherein the average grain size of the alloy as measured after recrystallization annealing, is not more than 5.5 μηι.

6. The superplastic aluminium alloy according to claim 5, wherein the recrystallization annealing is carried out at the temperature from 400 °C to 600 °C, preferably, from 490 °C to 540 °C, more preferably, at about 500 °C for about 15 minutes.

7. The superplastic aluminium alloy according to any one of claims 1 to 6, wherein the structure of the alloy is characterized by the presence of near spherical AlgFeNi particles having average particle size from about 1 to about 2 μιτι.

8. The superplastic aluminium alloy according to claim 7, wherein the volume fraction of the AlgFeNi particles is from about 4 to about 8 vol%.

9. The superplastic aluminium alloy according to claim 7, wherein the structure of the alloy is further characterized by the presence of finely dispersed AI₆(Mn,Cr) and AI₃Zr particles having average particle size of below about 100 nm.

10. The superplastic aluminium alloy according to claim 8, wherein the volume fraction of the finely dispersed AI₆(Mn,Cr) and AI₃Zr particles is from about 0.3 to about 6 vol%.

1 1. The superplastic aluminium alloy according to any one of claims 1 -10, wherein the alloy has at least one of the following characteristics measured at the room temperature:

yield strength from about 160 to about 250 MPa, and

tensile strength from about οτ 300 to 360 MPa.

12. The superplastic aluminium alloy according to claim 1 1 , wherein the alloy exhibits elongation of more than 430% at the strain rate of 0.001 -0.01 s^"1 and the temperature of 490- 540 °C.

13. The superplastic aluminium alloy according to any one of claims 1 -12, wherein the amounts of the alloy components are as follows, wt%:

magnesium 4.8

nickel 1 .0

iron 0.9

zirconium 0.25

chromium 0.05

manganese 0.05

aluminium and unavoidable impurities the balance.

14. A superplastic aluminium alloy comprising magnesium, nickel, iron, zirconium, chromium, manganese and scandium in the following amounts, wt%:

magnesium 3.3 to 5.9

nickel 0.6 to 1.2

iron 0.4 to 1.2

zirconium 0.12 to 0.35

chromium 0.03 to 0.4

manganese 0.03 to 0.9

scandium 0.05 to 0.50

aluminium and unavoidable impurities the balance.

15. The proposed superplastic aluminium alloy of claim 14, comprising magnesium, nickel, iron, zirconium, chromium, manganese and scandium in the following amounts, wt %:

magnesium 3.9 to 5.3

nickel 0.6 to 1.0

iron 0.6 to 1.0

zirconium 0.1 to 0.3

chromium 0.05 to 0.28

Manganese 0.05 to 0.75

scandium 0.1 to 0.3

aluminium and unavoidable impurities the balance.

16. The superplastic aluminium alloy of claim 14 or claim 15, wherein the amounts of the alloy components are as follows, wt%:

magnesium about 4.8

nickel about 0.9

iron about 0.7

zirconium about 0.2

chromium about 0.05

manganese about 0.05

scandium about 0.2

aluminium and unavoidable impurities the balance.

17. The superplastic aluminium alloy according to any one of claims 14 to 16, wherein the alloy has at least one of the following characteristics, as measured at the room temperature: yield strength of about 230-280 MPa, and

tensile strength of about 350-390 MPa.

18. The superplastic aluminium alloy according to any one of claims 14 to 17, wherein at the strain rate of 0.005-0.01 s^"1 and the temperature of 480-500 °C, the alloy exhibits elongation of more than 540%.

19. A product made of the superplastic aluminium alloy according to any one of claims 1 -

18.

20. The product of claim 19, wherein the product is in the form of a sheet material.

21 . The product of claim 20, wherein the thickness of the sheet material is from about 0.1 to about 10 mm.

22. The product of claim 21 , wherein the thickness of the sheet is from about 1 to about

2 mm.

23. A use of the superplastic aluminium alloy according to any one of claims 1 -18 for producing a product by superplastic forming.