Aluminum-based alloy

Abstract

The invention relates to the field of metallurgy, in particular to a non-heat-treatable wrought aluminum alloy based on an aluminum-magnesium-scandium system, which can be used as a material for structural elements (including welded structures). The aluminum-based alloy incapable of heat treatment deformation comprises the following components in percentage by weight: 3.0 to 5.2 percent of magnesium, 0.15 to 1.0 percent of manganese, 0.01 to 0.045 percent of scandium, 0.03 to 0.14 percent of zirconium, 0.025 to 0.18 percent of silicon, 0.01 to 0.05 percent of titanium, optionally added yttrium, at least one element (with the content of 0.01 to 0.55) selected from a group comprising copper and zinc, at least one element (with the content of 0.01 to 0.05) selected from a group comprising boron and carbon, and the balance of aluminum and inevitable impurities. The alloy has the characteristics of high strength, corrosion resistance, high elongation in an annealing state, excellent processability and the like.

Description

Technical Field

[0001] The present invention relates to non-ferrous metal metallurgy, in particular to a non-heat-treatable workable aluminum alloy based on the aluminum-magnesium-scandium system, which is used as a structural member material including welded structures and can be manufactured by forming operations. Prior Art

[0002] A currently widely used non-heat-treatable workable aluminum alloy based on the aluminum-magnesium-scandium system is the AMg5 grade alloy (according to GOST 4784-2019 standard), and its chemical composition is as follows by %wt:

[0003]

[0004] This alloy is widely used in many industries such as shipbuilding, aerospace engineering, construction, and transportation machinery manufacturing. This alloy is weldable using all welding processes and has high corrosion resistance. Its main drawback is the unsatisfactory strength properties.

[0005] A non-heat-treatable deformable alloy for cold-forming profiled products (such as containers, tanks, cans, etc., including welded structures) is known (WO 2018 / 187406A1, C22C3 / 00, B32B15 / 01, publication date October 11, 2018). This alloy is suitable for products that can be anodized, such as parts of household appliances, building components, and vehicle body parts.

[0006] The chemical composition of this alloy is as follows by %wt:

[0007]

[0008]

[0009] The drawback of this alloy is the insufficient strength due to the lack of elements that are easily soluble in aluminum (which can ensure solid solution strengthening) and the small number of transition metal additives (which can achieve strengthening by forming dispersed phases).

[0010] An Al-Mg-based aluminum alloy is known (patent number RU 2726520, C22C21 / 06, published on July 14, 2020). This alloy is designed for the production of rolled semi-finished products in the aerospace field, including sheets, sheets, stamped parts, and extruded profiles.

[0011] The chemical composition of this alloy is as follows by %wt:

[0012]

[0013] At least two elements selected from the following group:

[0014]

[0015] The main disadvantage of this alloy is the poor formability caused by the doping of a high content of strengthening elements (especially magnesium), and the additional addition of rare earth elements and scandium will exacerbate the cold deformation effect. In addition, the scandium content within the selected range results in poor economy in the application of this alloy due to the high cost of scandium. This alloy also contains beryllium elements that are harmful to health.

[0016] There is known an aluminum-magnesium alloy with a microcrystalline structure, which can be used to produce semi-finished products and parts for various industries by superplastic forming methods (Patent RU 2772479C1, C22C21 / 06, published on May 20, 2022).

[0017] The chemical composition of this alloy is as follows by wt%:

[0018]

[0019] The disadvantage of this alloy is that due to the presence of a large number of elements that can achieve strengthening by forming dispersed phases but will reduce plasticity, its elongation is insufficient.

[0020] There is known a weldable corrosion-resistant aluminum-magnesium alloy with a high magnesium content, which mainly contains an aluminum-scandium-zirconium ternary phase (Patent No. RU 2226565, C22C21 / 06, published on August 21, 1998). This alloy is designed to manufacture parts by welding and is applied to air transportation tools, mainly for the manufacture of aircraft components.

[0021] The chemical composition of this alloy is as follows by wt%:

[0022]

[0023] Containing certain elements from the following groups:

[0024] Scandium, terbium, cerium and other lanthanide elements 0.05 - 0.5

[0025] Among them, at least containing:

[0026] Scandium 0.1 - 0.2

[0027] Copper and / or zinc 0.1 - 0.4

[0028] Inevitable silicon impurities up to 0.1%.

[0029] The main disadvantage of this alloy is that the strengthening elements (especially magnesium) have a negative impact on cold stamping forming. The content of scandium and other lanthanide elements within the selected range results in a low cost - efficiency for the application of this alloy due to their high cost and the limited availability of lanthanide elements for mass production of semi - finished products made from this alloy.

[0030] There is known an aluminum - based alloy that can be used for manufacturing products that work in a corrosive environment and withstand high loads (including high and low temperatures) (patent number RU 2735846, C22C21 / 08, published on November 9, 2020). The alloy structure contains an aluminum solid solution and second - phase precipitates.

[0031] The chemical composition of this alloy is as follows in % wt:

[0032]

[0033] The disadvantage of this alloy is its insufficient formability, which is due to the presence of zirconium and scandium second - phase precipitates with an L12 lattice having a volume fraction exceeding 0.18%. Chromium is also contained in this alloy, which may form coarse intermetallic compounds and have a negative impact on the formability during the cold stamping process.

[0034] The closest analogue to the provided alloy is the non - heat - treatable 5182 - grade aluminum alloy (EN 573 - 3 standard), whose composition is as follows in % wt:

[0035]

[0036]

[0037] This alloy is applied in multiple industrial fields, including the production of sheets for automotive panels using cold stamping and stretching processes. This alloy has high workability and can produce parts with the required geometric shapes through forming processes. However, this alloy has low strength properties in the annealed state and cannot ensure sufficient weight efficiency for the manufactured products. Summary of the Invention

[0038] The present invention aims to develop a non - heat - treatable deformed aluminum - based alloy for manufacturing parts and structures (including welded structures) that can be processed through forming processes.

[0039] The achieved technical effect is to solve the above - mentioned technical problems and improve the strength while maintaining workability, corrosion resistance, and elongation.

[0040] This technical effect is achieved by the following non - heat - treatable wrought aluminum - based alloy: The alloy contains magnesium, manganese, scandium, zirconium, silicon, titanium, optionally yttrium (i.e., alternative alloy compositions with or without yttrium can be selected), and in addition, it contains at least one element selected from the group consisting of copper and zinc, and at least one element selected from the group consisting of boron and carbon. The content of each component is as follows in %wt:

[0041]

[0042]

[0043] According to another aspect, the present invention also relates to a product made of the above - mentioned aluminum alloy.

[0044] The description of "in total or individually" means the total content of the two elements or the content of only one (single) element, and in both cases, the numerical range is the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Shows the Erichsen test results, presented in the form of extrusion indentation before failure. DETAILED DESCRIPTION OF THE INVENTION

[0046] In the experimental tests of various alloy components, the following information about the alloy components was unexpectedly discovered:

[0047] The addition amount of magnesium should be 3.0%wt to 5.2%wt to ensure the required strength properties. Further increasing the magnesium content may have a negative impact on the plasticity of the material, complicate the production process of the rolled semi - finished product, and reduce its corrosion resistance. A lower magnesium content cannot guarantee the required strength properties of the alloy.

[0048] Adding 0.15%wt to 1.0%wt of manganese further increases the material strength by forming dispersed phases, and also improves the formability of the material. This effect is related to the fact that manganese can ensure the precipitation of iron - containing phases in a finer and more compact form.

[0049] The combined addition of 0.01%wt to 0.045%wt of scandium and 0.03%wt to 0.14%wt of zirconium ensures higher strength properties by forming nano - scale dispersed phases during the process heating in the semi - finished product production process. In addition, these elements have a modifying effect on both the casting and deformation structures of the material. The smaller recrystallized grain size promotes deformation through grain - boundary sliding, thus having a positive impact on the formability of the material.

[0050] Adding silicon in an amount exceeding 0.025% wt increases the alloy strength due to solid solution strengthening, thereby allowing for a reduction in the amount of expensive scandium required to achieve the desired strength. However, a silicon content exceeding 0.18% wt results in the formation of the Mg2Si crystallization phase, which reduces the workability during the hot rolling process and has a negative impact. Since the Mg2Si phase does not dissolve during the homogenization annealing process, its presence is highly undesirable.

[0051] Adding 0.01% wt to 0.05% wt of titanium ensures a fine-grained structure after deformation by forming compounds with aluminum as the crystallization nuclei during the casting process.

[0052] Adding 0.005% wt to 0.02% wt of yttrium further increases the strength and improves the corrosion resistance and formability by changing the particle shape of the iron-containing phase to a more favorable shape.

[0053] Selecting elements from the group including copper and zinc for doping, with a total or individual content of 0.01% wt to 0.55% wt, ensures further solid solution strengthening of the material. In addition, the natural aging process of the material further enhances the strengthening effect through precipitates. In alloys with a high magnesium content, the Al8Mg5β phase precipitates abundantly at the grain boundaries, making these alloys more prone to intergranular corrosion. Zinc precipitates serve as the starting point for the deposition of Al8Mg5. This promotes the deposition of the Al8Mg5 phase at the grain boundaries and within the grains, thereby reducing the tendency of intergranular corrosion. Since copper can form S'-Al2CuMg particles, which precipitate at the grain boundaries and lead to a reduction in corrosion resistance, its content in the alloy should be limited to within 0.55% wt.

[0054] To change the ingot structure and provide a uniformly sized and controlled grain after deformation of the semi-finished products made from this alloy, at least one element selected from the group of boron and carbon is added in an amount of 0.0001% to 0.005% wt. The added elements form compounds with each other and with aluminum, serving as the crystallization nuclei during the casting process to ensure a fine-grained structure in the ingot.

[0055] Providing a Si ≤ Zr + 2Sc ratio can exclude the precipitation of ternary phases with silicon and scandium and / or zirconium, the formation of which may lead to a reduction in the dispersion strengthening effect.

[0056] The provided alloy does not add chromium additionally to avoid the formation of coarse intermetallic compounds, which would reduce the stamping performance.

[0057] To reduce the adverse effects on the health of operators during the alloy production process, unlike alloys for similar applications, this alloy does not add beryllium.

[0058] Examples of Invention Embodiments

[0059] Example 1

[0060] The ingot with dimensions of 120×400×1200 mm is cast by the semi - continuous casting method. The chemical composition of the ingot is shown in Table 1.

[0061] After cutting off the head and tail parts, the ingot is subjected to a three - stage homogenization treatment. The first stage is to hold at 310 - 320 °C for 2 hours. The second stage is to hold at 380 - 390 °C for 4 hours. The third stage is to hold at 420 - 440 °C for 4 hours. After homogenization treatment, a rolling blank of 100×340×320 mm is cut. The flat blank is hot - rolled to a thickness of 6 mm at a temperature of 400 - 440 °C. Subsequently, an intermediate annealing at 290 - 330 °C is carried out, and then cold - rolled to a thickness of 1.0 mm. The rolled sheet is finally annealed at 280 - 320 °C.

[0062] Specimens are cut from the sheet for testing the tensile mechanical properties at room temperature, corrosion resistance and formability by the Erichsen extrusion method.

[0063] The tensile test is carried out on flat specimens according to the GOST 1497 - 84 standard. The technological test of the Erichsen sheet extrusion method is implemented according to the GOST 10510 - 80 standard. The intergranular corrosion test is carried out on 10×20 mm specimens using Solution No. 1 for 24 hours according to the GOST 9.021 - 74 standard.

[0064] The relevant mechanical properties, technological properties and corrosion test results are shown in detail in Table 2.

[0065] Table 1

[0066]

[0067] A - prototype

[0068] Table 2

[0069]

[0070] As shown in the comparison of the mechanical properties of the sheet in Table 2, the alloy of the present invention has higher strength properties compared with the prototype alloy while maintaining the elongation, formability and corrosion resistance. The most significant advantage of this alloy is its higher strength, which enables the products made from it to reduce the wall thickness, thereby improving the weight efficiency of the structures made from it. The maintained elongation and the results of the Erichsen extrusion test ensure the high processability of the material during the forming process. Figure 1 An example of the extrusion indentation of the developed alloy composition before failure is shown.

[0071] Example 2

[0072] Under industrial conditions, a billet with a diameter of 178 mm is cast by semi - continuous casting method. Its composition is shown in Table 3, and the following raw materials are used: at least A85 - grade aluminum ingots, zinc ingots, Mg - 90 - grade magnesium ingots, Cu80F master alloy, Kr - 90 - grade crystalline silicon, Al - 5Ti - 1B modification bars, and binary master alloys (Al - Zr10%, Al - Y2%, Al - Sc2%).

[0073] The billet is subjected to two - stage homogenization treatment. In the first stage, it is held at 350 °C for 4 hours. In the second stage, it is held at 450 °C for 6 hours. Profile No. 1 with a wall thickness of 6 mm is extruded from the billet. Before extrusion, the billet is heated to 440 - 460 °C. The extrusion speed of all alloy components including the prototype alloy is 0.3 mm / s. The surface quality and geometric dimensions of all extruded profiles meet the required parameters, indicating that the alloy has quite good processing performance.

[0074] Specimens are cut from the profiles for tensile mechanical property tests at room temperature.

[0075] The tensile test is carried out according to the GOST 1497 - 84 standard on flat specimens of the profiles in the hot - extruded state.

[0076] The results of the mechanical property tests are shown in Table 4.

[0077] Table 3

[0078]

[0079] A - prototype

[0080] Table 4

[0081]

[0082] As shown in Table 4, the comparison of the mechanical properties of the profiles indicates that the alloy of the present invention has higher strength properties compared to the prototype alloy while maintaining the elongation and extrusion processing performance. The most significant advantage of this alloy lies in its higher strength, which enables the products made from it to reduce the wall thickness, thereby improving the weight efficiency of the structures made from it.

[0083] Example 3

[0084] An ingot with dimensions of 120×400×1200 mm is cast by semi - continuous casting method. Its chemical composition is shown in Table 5. The first and second alloy compositions that meet the Si≤Zr + 2Sc ratio, and the third and fourth alloy compositions that do not meet this ratio are selected for research.

[0085] After removing the head and tail parts, the ingot is subjected to a three-stage homogenization treatment. In the first stage, it is held at 370 - 380 °C for 3 hours. In the second stage, it is held at 450 - 460 °C for 6 hours. After homogenization treatment, a rolled blank of 100×340×320 mm is cut. The flat blank is hot-rolled to a thickness of 6 mm at a temperature of 440 - 460 °C. Subsequently, it is subjected to an intermediate annealing at 290 - 330 °C and then cold-rolled to a thickness of 1.0 mm. The rolled sheet is finally annealed at 280 - 320 °C.

[0086] Specimens are cut from the sheet for testing the tensile mechanical properties at room temperature, the corrosion resistance, and the formability by the Erichsen extrusion method.

[0087] The tensile test is carried out on flat specimens in accordance with the GOST 1497 - 84 standard. The technological test of the Erichsen sheet extrusion method is implemented in accordance with the GOST 10510 - 80 standard. The intergranular corrosion test is carried out in accordance with the GOST 9.021 - 74 standard on 10×20 mm specimens using solution No. 1 for 24 hours.

[0088] The relevant mechanical properties, technological properties, and corrosion test results are shown in Table 6 in detail.

[0089] Table 5

[0090]

[0091] A - prototype

[0092] Table 6

[0093]

[0094] As shown in Table 5, the comparison of the mechanical properties of the profiles shows that failure to comply with the ratio of Si≤Zr + 2Sc will lead to deterioration of the plastic properties, which are characterized by a decrease in the elongation rate and a decrease in the indentation depth in the Erichsen test.

[0095] Now, a legal protection scope is applied for the non - heat - treatable wrought aluminum - based alloy, which contains elements such as magnesium, manganese, scandium, zirconium, silicon, titanium, etc. In addition, the alloy further contains at least one element selected from the group including copper and zinc, and at least one element selected from the group including boron and carbon, and the weight percentages of each component are as follows:

[0096]

[0097] It is recommended that the alloy also contains 0.005 - 0.02% by weight of yttrium, and the contents of scandium, zirconium, and silicon satisfy the ratio relationship of Si≤Zr + 2Sc to avoid the precipitation of ternary phases containing silicon, scandium, and / or zirconium. Under this condition, the silicon content is controlled within the range where no Mg2Si crystal phase is formed, and the alloy does not contain chromium and beryllium.

[0098] The alloy can be used to produce rolled semi-finished products by single-stage, two-stage or three-stage annealing processes, with at least one annealing stage being carried out at a temperature above the solution line to ensure the best effect of strengthening elements in the material. Under this process, the material has excellent properties in the recrystallized state: the tensile strength is not less than 300 MPa, the yield strength is not less than 160 MPa, and the elongation is not less than 20%.

[0099] The alloy is also suitable for the production of extruded semi-finished products and can ensure that the material has the following high performance: the tensile strength is not less than 320 MPa, the yield strength is not less than 190 MPa, and the elongation is not less than 15.5%.

[0100] The alloy can also be used for cold deformation processing of sheet semi-finished products. In this state, the material still maintains excellent properties: the tensile strength is not less than 300 MPa, the yield strength is not less than 160 MPa, and the elongation is not less than 20%.

Claims

1. A non-heat-treatable wrought aluminum-based alloy comprising magnesium, manganese, scandium, zirconium, silicon, titanium, and additionally comprising at least one element selected from the group consisting of copper and zinc, and at least one element selected from the group consisting of boron and carbon, with the proportions of the respective components being as follows in %wt:

2. The alloy according to claim 1, characterized in that It also contains 0.005 - 0.02%wt of yttrium.

3. The alloy according to claim 1, wherein the contents of scandium, zirconium, and silicon satisfy the proportional relationship of Si ≤ Zr + 2Sc to avoid the formation of ternary phase precipitates containing silicon, scandium, and / or zirconium.

4. The alloy according to claim 1, wherein the silicon content is controlled within a range where no Mg2Si crystal phase is formed, and the alloy does not contain chromium and beryllium.

5. The alloy according to any one of claims 1 - 4, which can produce a rolled semi-finished product by a single-stage, two-stage, or three-stage annealing process, wherein at least one annealing stage is carried out at a temperature above the solution line to ensure the best effect of the strengthening elements in the material; under this process, the material has the following excellent properties in the recrystallized state: the tensile strength is not less than 300 MPa, the yield strength is not less than 160 MPa, and the elongation is not less than 20%.

6. The alloy according to any one of claims 1 - 4, which is suitable for the production of extruded semi-finished products and can ensure that the material has the following high performance: the tensile strength is not less than 320 MPa, the yield strength is not less than 190 MPa, and the elongation is not less than 15.5%.

7. A product made from the aluminum alloy sheet semi-finished product according to any one of claims 1 - 5 by a cold deformation method; in this state, the material still maintains the following excellent properties: the tensile strength is not less than 300 MPa, the yield strength is not less than 160 MPa, and the elongation is not less than 20%.

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