RU2623932C1 - Deformable thermally refractory aluminium-based alloy - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: deformable thermally refractory aluminium-based alloy contains, wt %: magnesium 5.3-6.3; manganese 0.3-0.6; zirconium 0.08-0.15; beryllium 0.0001-0.005; scandium 0.09-0.14; titanium 0.01-0.03; gadolinium 0.06-0.10; iron 0.06-0.22; aluminium and unavoidable impurities - the rest, including silicon of not more than 0.12, zinc not more than 0.1 and copper not more than 0.1, with a total content of not more than 0.22, the ratio of gadolinium content to scandium content is of 0.5 to 0.9, and the ratio of iron content to silicon content is equal to or greater than one.

EFFECT: increasing the strength and plasticity of the material.

1 ex, 2 tbl

Description

The present invention relates to the field of metallurgy, in particular to wrought alloys based on aluminum, intended for use in the form of deformed semi-finished products, mainly in the form of sheets, as a structural material in aerospace engineering, shipbuilding, transport engineering and other industries.

Known deformable thermally unstrengthened alloy based on aluminum grade AMg61, used in the form of deformed semi-finished products as a structural material, containing, by weight. %:

Magnesium 5.5-6.5 Manganese 0.8-1.1 Zirconium 0.02-0.1 Beryllium 0.0001-0.005 Copper, no more 0.05 Zinc, no more 0.2 Iron, no more 0.2 Silicon, no more 0.2 Aluminum Rest

(see. Aluminum alloys. Industrial deformable sintered and cast aluminum alloys. Reference guide. M.: Metallurgy. 1972. P. 44-45).

However, the existing alloy has low strength properties.

Known deformable thermally non-hardening alloy based on aluminum, used in the form of deformed semi-finished products as a structural material (see patent RU 2081934, IPC С22С 21/06 - prototype), the following chemical composition, wt. %:

Magnesium 5.3-6.3 Manganese 0.2-0.7 Zirconium 0.02-0.15 Beryllium 0.0001-0.005 Scandium 0.17-0.35 At least one metal out group containing titanium and chrome 0.01-0.25 Aluminum Rest

The disadvantage of the prototype alloy is the insufficiently high strength and low ductility of the sheets made from it, which complicates the structure made of sheet materials and reduces its reliability. Another disadvantage of the prototype alloy is its rather high content of expensive scandium, which makes the alloy more expensive.

A deformable thermally non-hardenable aluminum-based alloy is proposed, containing magnesium, manganese, zirconium, beryllium, scandium and titanium, which additionally contains gadolinium, iron and inevitable impurities, the main of which are silicon, zinc and copper, in the following ratio of components, wt. %:

Magnesium 5.3-6.3 Manganese 0.3-0.6 Zirconium 0.08-0.15 Beryllium 0.0001-0.005 Scandium 0.09-0.14 Titanium 0.01-0.03 Gadolinium 0.06-0.10 Iron 0.06-0.22

Aluminum and inevitable impurities, including silicon in an amount of not more than 0.12 wt. %, zinc in an amount of not more than 0.1 wt. % and copper in an amount of not more than 0.1 wt. %, with a total content of impurities of silicon, zinc and copper not more than 0.22 wt. % - the rest. Moreover, the ratio of the content of gadolinium to the content of scandium should be from 0.5 to 0.9, and the ratio of the iron content to the silicon content should be equal to or greater than unity.

The proposed alloy differs from the known one in that it additionally contains gadolinium, iron and inevitable impurities, the main of which are silicon, zinc and copper, in the following ratio of components, wt. %:

Magnesium 5.3-6.3 Manganese 0.3-0.6 Zirconium 0.08-0.15 Beryllium 0.0001-0.005 Scandium 0.09-0.14 Titanium 0.01-0.03 Gadolinium 0.06-0.10 Iron 0.06-0.22

Aluminum and inevitable impurities, including silicon in an amount of not more than 0.12 wt. %, zinc in an amount of not more than 0.1 wt. % and copper in an amount of not more than 0.1 wt. %, with a total content of impurities of silicon, zinc and copper not more than 0.22 wt. % - the rest. Moreover, the ratio of the content of gadolinium to the content of scandium should be from 0.5 to 0.9, and the ratio of the iron content to the silicon content should be equal to or greater than unity.

The difference of the proposed alloy is also that the ratio between the iron content and the inevitable impurity of silicon in the alloy should be at least one. In addition, the proposed alloy has a lower scandium content.

The technical result is an increase in strength and ductility, which allows to reduce the weight of the structure and increase its reliability, as well as reducing the cost of the alloy, which will reduce the cost of structural elements made of the proposed alloy, and the structure as a whole.

With the proposed content and ratio of components during crystallization of the alloy ingot of the proposed composition, a supersaturated solid solution of the main alloying components (Mg, Mn, Zr, Sc, Gd) in aluminum is formed. During subsequent inevitable technological heating of the ingot, the supersaturated solid solution decomposes, and the decomposition products are dispersed nanosized particles of the Al ₃ phase (Sc, Zr, Gd), which have a strong strengthening effect both directly and due to the formation of unrecrystallized (polygonized) in the deformed semi-finished product structure. With the proposed ratio between the content of scandium and gadolinium, the most complete assimilation of these elements by the melt is ensured, which ensures maximum hardening during subsequent decomposition of the solid solution. The bulk of magnesium and manganese remains in the alloy matrix, providing solid solution hardening. Titanium is part of the hardening phase Al ₃ (Sc, Zr, Gd), dissolving in it and thereby increasing the strength of the alloy. With the proposed content of Sc, Zr and Gd in the alloy and the proposed ratio between the content of these elements, the Al ₃ phase (Sc, Zr, Gd) formed during the decomposition of the solid solution has high thermal stability, which allows to increase the temperature of technological heating and prevent possible softening of the material due to coagulation decay products. Particles of the Al ₃ phase (Sc, Zr, Gd) are highly resistant to cutting by their dislocations, which leads to additional hardening of the alloy due to an increase in the density of dislocations. The addition of iron to the alloy forms particles of the Al (Fe, Mn) phase of crystallization origin, which contribute to the hardening of the alloy. Beryllium microadditive protects melting from oxidation and burning of magnesium, which also contributes to hardening of the alloy. With the proposed content of Sc, Zr and Gd in the alloy and the proposed ratio between the content of these components, the probability of the formation of coarse primary Al ₃ intermetallic compounds (Sc, Zr, Gd) is reduced, which increases the ductility of the alloy. The increase in ductility of the alloy is also promoted by the limitation of the content of inevitable impurities of silicon, zinc and copper. The proposed ratio between the iron and silicon content improves the casting properties of the alloy. Reducing the content of expensive scandium in the proposed alloy and its partial replacement with zirconium and gadolinium, the cost of which is an order of magnitude lower than the cost of scandium, reduces the cost of the proposed alloy and deformed semi-finished products made from it.

Example

Received the proposed alloy from a mixture consisting of aluminum A7, Mg Mg90 and double ligatures aluminum-manganese, aluminum-zirconium, aluminum-beryllium, aluminum-scandium, aluminum-titanium, aluminum-gadolinium and aluminum-iron. The alloy was prepared in an electric crucible furnace and flat ingots 16 × 160 × 200 mm in size were cast. The chemical composition of the alloy is shown in table 1.

The ingots were homogenized, then machined to a thickness of 14 mm, then heated to 400 ° C and hot rolled to a thickness of 6 mm, then at 100 ° C to a thickness of 2.8 mm. The resulting sheets with a thickness of 2.8 mm were annealed at 320 ° C for 1 h. The annealed sheets were tested at room temperature with the ultimate strength σ _B and elongation δ determined on standard flat samples with a working part width of 10 mm (GOST 11701-84), carved in a shared direction. Also, tests were made in the same way of sheets of prototype alloy containing, by weight. %: magnesium 5.8, manganese 0.41, zirconium 0.13, beryllium 0.001, scandium 0.19, titanium 0.04, aluminum - the rest. The test results of the sheets are shown in table 2.

Thus, the proposed alloy has about 5% higher tensile strength and about 1.3 times higher relative elongation, which will allow about 5% to reduce the weight of the structure and, accordingly, increase the characteristics of the weight recoil, and also will increase the reliability of structures made from a thin sheet, for example, fuel tanks, which is extremely important for space technology. In addition, due to the fact that the proposed alloy contains about 47% less expensive scandium, its cost can be reduced accordingly.

Claims (4)

Wrought thermally non-hardening aluminum-based alloy containing magnesium, manganese, zirconium, beryllium, scandium, titanium, aluminum and inevitable impurities, characterized in that it additionally contains gadolinium and iron in the following ratio, wt.%: magnesium 5.3-6.3 manganese 0.3-0.6 zirconium 0.08-0.15 beryllium 0.0001-0.005 scandium 0.09-0.14 titanium 0.01-0.03 gadolinium 0.06-0.10 iron 0.06-0.22 aluminum and inevitable impurities, including silicon not more than 0.12, zinc not more than 0.1, copper not more than 0.1, with their total content not more than 0.22 - the rest,  wherein the ratio of gadolinium content to scandium content is from 0.5 to 0.9, and the ratio of iron content to silicon content is equal to or greater than unity.