Patent Description:
The proposed alloy is primarily intended for use in vehicles such as hulls of boats and other ships, hull parts, plating and other loaded members of aircraft, truck and railway tanks, in particular, for transportation of chemically active substances, as well as for use in the food industry, etc..

Due to their high corrosion resistance, weldability, high elongation values and their ability to operate at cryogenic temperatures, wrought alloys of the Al-Mg system (series 5xxx) have been widely used for products operating in corrosive environments, in particular, they are intended for use in river and seawater (water transport, pipelines, etc.), tanks for transportation of liquefied gas and chemically active liquids.

The main disadvantage of alloys of series 5xxx is the low level of strength properties of as-annealed wrought semi-finished products; for example, the yield strength of alloys of type <NUM> after annealing does not usually exceed <NUM> MPa (see Industrial aluminium alloys: Reference book.

One of the ways to improve the strength properties of as-annealed alloys 5xxx is additional alloying with transition metals, among which Zr and, to a lesser extent, Hf, V, Er and some other elements have gained the widest use. The principal distinctive feature of such alloys, in this instance, from other known alloys of the Al-Mg system (of type <NUM>) is the content of elements forming dispersoids, in particular, with the lattice of type L1<NUM>. In this instance, the combined effect of increasing the strength properties is achieved by solid-solution hardening of the aluminium solid solution, mainly, with magnesium, and the presence in the structure of various secondary phases of precipitations formed during homogenization (heterogenization) annealing.

So, an alloy claimed by Alcoa is known (<CIT>). The material contains (% wt): magnesium <NUM>-<NUM>, manganese <NUM>-<NUM>, zinc <NUM>-<NUM>, zirconium up to <NUM>, chromium up to <NUM>, titanium up to <NUM>, iron up to <NUM>, silicon up to <NUM>, copper <NUM>-<NUM>, calcium up to <NUM>, beryllium up to <NUM>, at least one element from the group: boron, carbon, each up to <NUM>, at least one element from the group: bismuth, lead, tin, each up to <NUM>, scandium, silver, lithium, each up to <NUM>, vanadium, cerium, yttrium each up to <NUM>, at least one element from the group: nickel and cobalt, each up to <NUM>, the balance is aluminium and unavoidable impurities, with the total magnesium and zinc content of <NUM>-<NUM>% wt and the total iron, cobalt and/or nickel content of no more than <NUM>% wt, the balance is aluminium and unavoidable impurities. Among the disadvantages of this alloy, the relatively low overall level of strength properties, which sometimes limits the use, should be noted. The presence of many small additives reduces the production rate, which affects adversely the performance of foundry facilities, and the high content of magnesium leads to a decrease in processability and corrosion resistance.

A much greater effect of increasing the strength properties than that in alloys of type <NUM> is reached with the combined content of scandium and zirconium additives. In this instance, the effect is achieved by the formation of a much larger amount of precipitations (with the typical size of <NUM>-<NUM>), resistant to high-temperature heating during deformation processing and subsequent annealing of wrought semi-finished products, which provides a higher level of strength properties.

For example, a material based on the Al-Mg system, alloyed jointly with zirconium and scandium additives, is known; in particular, CRISM "Prometey" claimed the material, disclosed in <CIT>, which is known as alloy <NUM>-<NUM>. The alloy is characterized by a higher level of strength properties than alloys of types <NUM> and <NUM>. The claimed material contains (% wt) magnesium <NUM>-<NUM>%, scandium <NUM>-<NUM>%, manganese <NUM>-<NUM>%, chromium <NUM>-<NUM>%, zirconium <NUM>-<NUM>, titanium <NUM>-<NUM>%, zinc <NUM>-<NUM>%, boron <NUM>-<NUM>%, beryllium <NUM>-<NUM>%, and the balance is aluminium. Among the disadvantages of the material, the content of a large amount of magnesium should be noted, which sometimes affects adversely the processability during deformation processing, and the presence of the β-Al<NUM>Mg<NUM>phase in the final structure leading, in some instances, to a decrease in corrosion resistance.

A material claimed in <CIT> of Kaiser Aluminium is also known. An alloy based on the Al-Mg-Sc system, which additionally contains elements selected from the group including Hf, Mn, Zr, Cu and Zn, in particular (% wt) <NUM>-<NUM>% Mg, <NUM>-<NUM>% Sc as well as <NUM>-<NUM>% Hf and/or <NUM>-<NUM>% Zr, <NUM>-<NUM>% Cu and/or <NUM>-<NUM>% Zn, is claimed. In a particular version, the material may contain additionally <NUM>-<NUM>% wt Mn. Among the disadvantages of the claimed material, the relatively low values of strength properties should be noted with the magnesium content at the lower limit as well as the low corrosion resistance and the low processability during deformation processing with the magnesium content at the upper limit. At the same time, to ensure a high level of properties, it is necessary to regulate the ratio of the size of particles formed by such elements as Sc, Hf, Mn and Zr.

A material, claimed by Aluminium Company of America and described in <CIT>, is known. The aluminium-based alloy contains (% wt) magnesium <NUM>-<NUM>%, zirconium <NUM>-<NUM>%, manganese <NUM>-<NUM>%, silicon up to <NUM>% and about <NUM>-<NUM>% of elements, forming precipitations, which are selected from the group: Sc, Er, Y, Cd, Ho, Hf; the balance is aluminium and foreign elements and impurities. Among the disadvantages, the relatively low values of strength properties should be noted when using alloying elements within the lower range.

A material of RUSAL, described in patent <CIT>, is known. The aluminium-based alloy contains (% wt) zirconium <NUM>-<NUM>%, iron <NUM>-<NUM>%, manganese <NUM>-<NUM>%, chromium <NUM> - <NUM>%, scandium <NUM>-<NUM>%, titanium <NUM>-<NUM>%, at least one element selected from the group: silicon <NUM>-<NUM>%, cerium <NUM>-<NUM>%, calcium <NUM>-<NUM>% and optionally magnesium <NUM> to <NUM>%.

A material, claimed by NanoAl and described in application <CIT>, is known. The alloy contains aluminium, magnesium, manganese, silicon, zirconium and nanoparticles of Al<NUM>Zr L12 with the average size of about <NUM>, in the amount of <NUM><NUM> <NUM>/m<NUM> and more; besides, the particles contain one or more elements from the group of tin, strontium and zinc; the aluminium alloy in the work-hardened condition has the yield strength of at least about <NUM> MPa, the ultimate tensile strength of at least about <NUM> MPa and the elongation of at least about <NUM>% at room temperature; and that in the annealed condition has the yield strength of at least about <NUM> MPa, the ultimate tensile strength of at least about <NUM> MPa and the elongation of at least about <NUM>%. Among the disadvantages of the condition alloy, the low level of strength in the annealed condition should be noted.

<CIT> discloses high strength weldable Al-Mg alloy, having high strength, excellent corrosion resistance and weldability. Said aluminium alloy product is composed of (in wt. %): Mg <NUM> to <NUM>, Mn <NUM> to <NUM>, Fe < <NUM>, Si < <NUM>, Cu < <NUM>, Zr < <NUM>, Cr < <NUM>, Ti <NUM> to <NUM>, Sc < <NUM>, Zn < <NUM>, Li < <NUM>, Ag < <NUM>, optionally one or more of the following dispersoid forming elements selected from the group consisting of erbium, yttrium, hafnium, vanadium, each < <NUM> wt%, and impurities or incidental elements each < <NUM>, total < <NUM> and the balance being aluminium.

The prototype is the technical solution known from the invention under <CIT> of Eads Deutschland Gmbh. In particular, the weldable, corrosion-resistant material with the triple-phase Al, Zr, Sc, containing, mainly, (% wt) magnesium <NUM>-<NUM>%, zirconium <NUM>-<NUM>%, manganese <NUM>-<NUM>%, titanium <NUM>-<NUM>%, totally <NUM>-<NUM>% of scandium and terbium and optionally at least one additional element selected from the group consisting of several lanthanides, in which scandium and terbium are present as mandatory elements, and at least one element selected from the group that includes copper <NUM>-<NUM>% and zinc <NUM>-<NUM>%; the balance is aluminium and unavoidable impurities of no more than <NUM>% silicon. Among the disadvantages of this material, the presence of rare and expensive elements should be noted. Moreover, this material can be not resistant enough to high-temperature heating during process heating.

The objective of the invention is the creation of a new high-strength aluminium alloy, characterized by a low cost and a set of high-level physical and mechanical properties, processability and corrosion resistance, in particular, having a high level of mechanical properties after annealing (temporary resistance minimum <NUM> MPa, yield strength minimum <NUM> MPa and elongation minimum <NUM>%) and a high processability during hot and cold deformation.

The technical result is the solution of the objective and ensuring a high processability during deformation processing while increasing the mechanical properties of the alloy due to precipitations of the Zr-containing phase with the crystal lattice of type L1<NUM>.

The solution of this objective and the achievement of the specified technical result is ensured by the fact that an alloy is claimed with the structure consisting of an aluminium solution, precipitations and a eutectic liquid phase formed by such elements as magnesium, manganese, iron, chromium, zirconium, titanium and vanadium. Said alloy contains additionally silicon and scandium; and at least <NUM>% of the share of each element from the group of zirconium and scandium form precipitations with the lattice of type L1<NUM> in the amount of at least <NUM>% vol, with the following redistribution of alloying elements (% wt):.

Aluminium and unavoidable impurities balance,
wherein the aluminum alloy structure comprises a minimally alloyed aluminium solution and precipitation particles, in particular phases Al<NUM>Mn with a size of up to <NUM>, Al<NUM>Cr with a size of up to <NUM> and particles of type Al<NUM>Zr and/or Al<NUM>(Zr,Sc) and/or Al<NUM>(Zr,V) with the lattice of type L1<NUM> with a size of up to <NUM>.

Unexpectedly, it has been found that the effect of the increased level of strength properties is achieved from the combined positive effect of solid-solution hardening of the aluminium solution due to magnesium and secondary phases containing manganese, chromium, zirconium, scandium and vanadium, which are resistant to high-temperature heating. At the same time, due to additional alloying of the alloy with silicon and vanadium, the solubility of zirconium and scandium in the aluminium solution decreases, increasing the volume fraction of the number of precipitation particles with the size of up to <NUM> and improving the efficiency of hardening.

In this instance, the aluminium alloy structure must contain the minimally alloyed aluminium solution and precipitation particles, in particular, phases Al<NUM>Mn with the size of up to <NUM>, Al<NUM>Cr with the size of up to <NUM> and particles of type Al<NUM>Zr and/or Al<NUM>(Zr,Sc) and/or Al<NUM>(Zr,V) with the lattice of type L1<NUM> with the size of up to <NUM>.

The justification of the claimed amounts of alloying components that ensure the achievement of the given structure in this alloy is given below.

Magnesium in the amount of <NUM>-<NUM>% wt is required to increase the overall level of mechanical properties due to solid-solution hardening. If the content of magnesium is higher than the stated content, the effect of this element will lead to a reduction in processability during the metalworking process, for example, when rolling ingots, having a significant negative impact on the yield ratio in deformation. The content below <NUM>% wt will not provide the minimum required level of strength properties.

Zirconium in the amount of <NUM>-<NUM>% wt is necessary to ensure dispersion hardening with the formation of precipitations of phases of type Al<NUM>Zr L1<NUM> or Al<NUM>(Zr,Sc) and/or Al<NUM>(Zr,V) in the presence of relevant elements.

Scandium and vanadium in the amount of <NUM>-<NUM>% wt and <NUM>-<NUM>% wt respectively are necessary to ensure the required level of strength properties due to dispersion hardening with the formation of precipitations of metastable phases additionally containing zirconium with the L1<NUM>-type crystal lattice.

In general, zirconium, scandium, and vanadium are redistributed between the aluminium matrix and precipitations of the metastable Al<NUM>Zr phase with the lattice of type L1<NUM>, and the number of particles is determined by solubility of such elements at the decomposition temperature.

If the concentration of zirconium in the alloy is higher than <NUM>% wt, the use of elevated melting temperatures is required, which, in some instances, is not technically feasible under the conditions of semi-continuous casting of ingots.

When using standard casting conditions with the zirconium content of above <NUM>% wt, it is possible to form the phase with the lattice of type D0<NUM> in the structure of primary crystals, which is unacceptable.

The zirconium, scandium and vanadium content below the stated level will not provide the minimum required level of strength properties due to the insufficient amount of precipitations of secondary phases with the lattice of type L1<NUM>.

Chromium in the amount of <NUM>-<NUM>% wt is necessary to increase the overall level of mechanical properties due to dispersion hardening with the formation of the secondary phase of Al<NUM>Cr. If the content of chromium is higher than the stated content, the effect of this element will lead to a reduction in processability during the metalworking process, for example, when rolling ingots, which will have a significant negative impact on the yield ratio in deformation. The content below <NUM>% wt will not provide the minimum required level of strength properties.

Manganese in the amount of <NUM>-<NUM>% wt is necessary to increase the overall level of mechanical properties due to dispersion hardening with the formation of the secondary phase of Al<NUM>Mn. If the content of manganese is higher than the stated content, the effect of this element will lead to a reduction in processability during the metalworking process, for example, when rolling ingots, due to the possible formation of primary crystals, having a significant negative impact on the yield ratio in deformation. The content below <NUM>% wt will not provide the minimum required level of strength properties. When the content is higher than <NUM>% wt, primary crystals of the Al<NUM>Mn phase, which reduce processability during deformation processing, will be formed.

Silicon is required to reduce the solubility of zirconium, scandium and vanadium in the aluminium solution; as a result, the main effect of these elements will be associated with the increase in supersaturation of zirconium, scandium and vanadium in the aluminium solution during casting of billets, which will ensure the release of more secondary phase dispersoids with the L1<NUM> lattice during subsequent homogenization annealing and improve the effect of dispersion hardening. Moreover, it has been experimentally established that, in the presence of silicon, less than <NUM>% of the share of zirconium and scandium of the alloy, in the range of the claimed concentrations of alloying elements, form precipitations with the lattice of type L1<NUM> in the amount of at least <NUM>% vol. With the silicon content of less than <NUM>% wt. , there has not been any effect as to a reduction in solubility of zirconium and scandium in the aluminium solution. With the content of above <NUM>% wt, the crystallization phase of Mg2Si, which reduces processability during hot rolling, is formed and has a negative impact. The presence of the Mg2Si phase is highly undesirable as it does not dissolve during homogenization annealing.

<NUM> alloys were produced under laboratory conditions, the chemical composition of which is shown in Table <NUM>. Alloys <NUM> and <NUM> are according to the invention.

The alloys were prepared in a laboratory induction kiln, with the mass of each cast of at least <NUM>. The following materials were used as charge materials (% wt): aluminium A99 (<NUM>% Al), magnesium Mg90 (<NUM>% Mg), alloying compositions Al-<NUM>%Mn, Al-<NUM>%Fe, Al-<NUM>%Cr, Al-<NUM>%Zr, Al-<NUM>%Ti, Al-<NUM>%V, Al-<NUM>%Sc, Al-<NUM>%Si. The cross section of cast ingots was 200x50 mm, and the length was about <NUM>. The estimated alloys cooling rate in the solidification range did not exceed <NUM>/s.

Cast ingots were homogenized under the conditions when the maximum temperature of heating and holding did not exceed <NUM>. Then hot and cold rolling of ingots into sheets was carried out according to the following scheme: hot rolling temperature <NUM> and total deformation degree <NUM>% down to <NUM>, intermediate annealing of the hot-rolled billet at the temperature of <NUM>, cold rolling with the total degree of deformation of <NUM>% down to the thickness of <NUM>. The mechanical properties of the sheets were determined after annealing at the temperature of <NUM> for <NUM> hours, the results of which are shown in Table <NUM>. The mechanical properties were evaluated based on the results of the determination of the ultimate tensile strength (UTS), yield strength (YS) and elongation (El). The gauge length of flat specimens was <NUM>, and the test speed was <NUM>/min.

The amount of precipitations was determined using computational and experimental methods, in particular, using the Thermocalc software package and analysis of the structure of homogenized ingots and annealed sheets of experimental compositions. The results are given in Table <NUM>.

The results show that only compositions <NUM>-<NUM> meet the requirements for the level of strength properties. Composition <NUM> ruptured during hot deformation processing due to the presence of primary crystals of the AL6(Fe,Mn) phase.

Claim 1:
Aluminium alloy with the structure, consisting of an aluminium solution, precipitations and a eutectic phase, formed by such elements as magnesium, manganese, iron, chromium, zirconium, titanium, vanadium, characterized in that the alloy additionally contains silicon and scandium and at least <NUM>% share of each element from the group of zirconium and scandium form precipitations with the lattice of type L1<NUM> in the amount of at least <NUM>% vol, with the following redistribution of alloying elements (% wt):

<TAB>

Aluminium and unavoidable impurities balance,
wherein the aluminum alloy structure comprises a minimally alloyed aluminium solution and precipitation particles, in particular phases Al<NUM>Mn with a size of up to <NUM>, Al<NUM>Cr with a size of up to <NUM> and particles of type Al<NUM>Zr and/or Al<NUM>(Zr,Sc) and/or Al<NUM>(Zr,V) with the lattice of type L1<NUM> with a size of up to <NUM>.