A high-strength and high-corrosion-resistant Al-Mg aluminum alloy and its preparation method

Abstract

A high-strength and high-corrosion-resistant Al-Mg series aluminum alloy and a preparation method thereof belong to the field of non-ferrous metal technology. The alloy composition includes: Mg 2.8%~6%, Mn 0.1%~1.4%, Cr 0.01%~0.24%, Mo 0.01%~0.24%, Fe 0%~0.5%, and the rest is Al, and is prepared by processes such as smelting, homogenization heat treatment, rolling and annealing. The introduction of Mo and Cr reduces the precipitation driving force of Mg, inhibits the formation of β phase at the grain boundary, reduces grain boundary corrosion, and improves the density of the oxide film, thereby enhancing corrosion resistance; Mn, Cr, and Mo jointly promote the dispersion distribution of the second phase, achieve tissue refinement, and improve comprehensive mechanical properties. The present invention achieves a good balance between strength and corrosion resistance through composition optimization and process control, meeting the application requirements of high-performance aluminum alloys in fields such as aerospace, automobiles, and marine engineering.

Description

Technical Field

[0001] The present invention belongs to the technical field of nonferrous metals, and in particular relates to a high-strength and high-corrosion-resistant Al-Mg series aluminum alloy and a preparation method thereof. Background Art

[0002] Aluminum is a widely present element in nature, with an average content of 8.7% in the Earth's crust, second only to oxygen and silicon. It possesses many excellent properties, such as low density, high plasticity, good thermal conductivity, and strong corrosion resistance. It can also be combined with other metals and non-metallic elements to form various aluminum alloys, leading to its growing industrial application. Furthermore, aluminum is recyclable. By adding other metals or non-metallic elements to pure aluminum, various aluminum alloys suitable for machining or casting can be prepared. The many inherent advantages of aluminum and its alloys have led to their increasing importance and widespread application in industry.

[0003] Al-Mg alloys are medium-strength aluminum alloys widely used in structural materials. They possess many excellent properties, such as strength, fatigue resistance, corrosion resistance, and weldability, and are therefore widely used in areas such as hull structures and superstructures of large ships. Currently, Al-Mg alloys are widely used in ships and industrial structures, but their strength and corrosion resistance remain insufficient in marine environments. The present invention effectively enhances the corrosion resistance and mechanical properties of Al-Mg alloys by adding Cr and Mo elements.

[0004] The addition of chromium (Cr) plays multiple crucial roles in Al-Mg alloys. First, it significantly enhances the alloy's corrosion resistance, demonstrating exceptional corrosion resistance in marine and industrial environments. Second, Cr has a low solubility in aluminum alloys. While a small amount dissolves in the aluminum matrix, acting as a solid solution strengthener, the majority exists as second-phase particles such as Al6Mn and Al7Cr. These second-phase particles hinder dislocation motion, thereby raising the alloy's recrystallization temperature and inhibiting the recrystallization process, thereby enhancing the alloy's strength and toughness. Furthermore, the addition of Cr helps inhibit intergranular corrosion, particularly in Al-Mg alloys with high magnesium content, where Cr forms stable compounds with magnesium, preventing its excessive precipitation. Overall, Cr not only improves the overall mechanical properties of Al-Mg alloys but also enhances their corrosion and wear resistance, making them suitable for demanding industrial and marine applications. However, when the Cr content is too high, it may form coarse intermetallic compounds with other alloying elements or impurities, resulting in a decrease in the alloy's formability. Therefore, controlling the chromium content is crucial for optimizing the properties of aluminum alloys.

[0005] Furthermore, the addition of molybdenum (Mo) significantly enhances the overall performance of aluminum alloys. First, Mo significantly improves the alloy's corrosion resistance, particularly in harsh environments such as prolonged high temperature, high humidity, and salt spray. Its addition enhances the alloy's oxidation and corrosion resistance. Second, Mo refines the grain structure by forming fine second-phase particles, thereby increasing the alloy's strength and hardness. Furthermore, Mo addition improves the alloy's heat resistance, enhancing its stability in high-temperature environments. Studies have shown that the combined addition of trace amounts of Mo and Mn significantly improves the heat resistance of Al alloys. In tensile tests, the combined addition of Mn and Mo significantly enhances the alloy's mechanical properties. In particular, under T6 peak aging conditions, the alloy containing Mn and Mo exhibits higher ultimate tensile strength (UTS) and 16% higher ductility, demonstrating superior mechanical properties compared to the alloy without Mo and Mn additions. Furthermore, Mo effectively inhibits the excessive precipitation of elements such as magnesium and silicon, reducing intergranular corrosion and thus improving the alloy's mechanical properties. In general, the Mo element plays an important role in improving the corrosion resistance, heat resistance and mechanical properties of Al-Mg alloys, making them more suitable for applications in high temperature and corrosive environments. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the present invention provides a high-strength and high-corrosion-resistant Al-Mg aluminum alloy and a preparation method thereof. By adding appropriate amounts of Mo and Cr elements, the obtained alloy maintains high strength while improving corrosion resistance.

[0007] A high-strength and high-corrosion-resistant Al-Mg aluminum alloy, the chemical composition of which, in percentage by mass, comprises: Mg 2.80% to 6.00%, Mn 0.10% to 1.40%, Cr 0.01% to 0.24%, Mo 0.01% to 0.24%, Fe 0.00% to 0.50%, with the remainder being Al, and the alloy must also satisfy the following conditions: 0.65≤Mn+Mo+Fe+Cr≤1.75, and Mn / Cr>3;

[0008] The mass fraction of impurities in the high-strength and high-corrosion-resistant Al-Mg aluminum alloy is ≤0.30%, and the mass fraction of a single element in the impurities is ≤0.05%.

[0009] The high-strength and high-corrosion-resistant Al-Mg aluminum alloy has a yield strength of 370 MPa to 400 MPa, a tensile strength of 230 MPa to 268 MPa, an elongation of 14% to 18%, and a corrosion mass loss of 17 mg cm -2 ~37 mg cm -2 .

[0010] The method for preparing the above-mentioned high-strength and high-corrosion-resistant Al-Mg aluminum alloy specifically comprises the following steps:

[0011] (1) Preheat pure aluminum, pure magnesium, pure iron and aluminum-based master alloy for standby use;

[0012] (2) Under protective atmosphere conditions, the pure aluminum obtained in step (1) is added to a preheated smelting furnace and the temperature is raised again. After all the pure aluminum is melted, stirring and slag removal are carried out in a timely manner to obtain an aluminum melt;

[0013] (3) Under protective atmosphere conditions, preheated pure iron and aluminum-based master alloy are added to the aluminum melt and stirred until completely melted. Preheated pure magnesium is added to the resulting melt and stirred again. After the pure magnesium is melted, hexachloroethane is added for degassing, and the mixture is stirred and skimmed to obtain a melt;

[0014] (4) Under protective atmosphere conditions, the melt is heated again, the slag is removed again, and then cast into a water-cooled copper mold to obtain a cast billet;

[0015] (5) subjecting the as-cast billet to a two-stage homogenization heat treatment, followed by hot rolling and cold rolling in sequence to obtain a cold-deformed alloy;

[0016] (6) The cold-deformed alloy is subjected to stabilization annealing treatment to obtain a high-strength and high-corrosion-resistant Al-Mg aluminum alloy.

[0017] in:

[0018] In the step (1), the purity of pure aluminum, pure magnesium and pure iron is ≥99.98%, the aluminum-based master alloy is specifically Al-10Mn, Al-10Cr and Al-5Mo, and the preheating temperature is 150°C to 350°C.

[0019] In the step (2), the preheating temperature of the smelting furnace is 400°C to 450°C, the smelting temperature of pure aluminum is 760°C to 780°C, and the holding time is 30 min to 40 min.

[0020] In the step (3), the melting temperature of the pure iron and aluminum-based master alloy is 740° C. to 760° C., and the holding time is 10 min to 15 min.

[0021] In the step (3), pure magnesium is added to the melt by pressing it into a bell jar, and is kept for 2 min to 4 min after pressing. The melting temperature of pure magnesium is 680°C to 700°C, and the holding time is 10 min to 15 min.

[0022] In the step (3), the amount of hexachloroethane added is 13 g / m 3 ~22 g / m 3 , the degassing time is 3 min~10 min.

[0023] In steps (2) and (3), the stirring speed is 180 r / min to 250 r / min, and the stirring time is 3 min to 5 min.

[0024] In the steps (2) to (4), the protective atmosphere is argon.

[0025] In the step (4), the melt is heated to 710°C to 730°C, and then slag is removed again.

[0026] In the step (4), the water pressure of the cooling water during the casting process is controlled to be 0.08 MPa to 0.30 MPa, and the solidification rate of the molten liquid in the water-cooled copper mold is 180 mm / min to 420 mm / min.

[0027] In the step (5), the double-stage homogenization heat treatment is specifically as follows: the as-cast billet is kept at 290°C to 380°C for 7 h to 9 h, then the temperature is raised to 490°C to 560°C and kept at that temperature for 9 h to 11 h.

[0028] In step (5), the hot rolling and cold rolling processes are as follows: hot rolling the as-cast billet at a temperature of 420°C to 470°C with a reduction of 65% to 82%, performing an intermediate heat treatment at 300°C to 370°C after hot rolling, keeping the temperature for 15 min to 35 min, and then cold rolling at room temperature with a reduction of 45% to 60%;

[0029] The hot rolling deformation process is divided into 6 to 15 passes, with an initial reduction rate of 5% to 10%, a mid-term reduction rate of 15% to 32%, and a late reduction rate of 25% to 40%.

[0030] In the step (6), the stabilization annealing treatment is specifically as follows: the alloy after cold deformation is kept at a temperature of 90°C to 300°C for 1 h to 5 h, and the cooling method is air cooling.

[0031] In the step (6), the high-strength and high-corrosion-resistant Al-Mg aluminum alloy is specifically a plate with a thickness of 10 mm to 20 mm and a width of 75 mm to 85 mm.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. This invention, by adding Mo and Cr to the Al-Mg alloy, reduces the driving force for Mg precipitation and mitigates intergranular corrosion. It also promotes the segregation of Mg atoms within grains, inhibiting their diffusion toward grain boundaries and effectively reducing the formation of β-phase at grain boundaries. Furthermore, the addition of Mo and Cr increases the density of the oxide film on the aluminum alloy surface, further enhancing its intergranular corrosion resistance and mechanical properties, thus meeting the requirements for high-performance aluminum alloys.

[0034] 2. The present invention achieves a dispersed distribution of the second phase within the Al-Mg alloy by adding Mn, Cr, and Mo. This not only effectively refines the size of the second phase but also increases its quantity, significantly improving the alloy's strength.

[0035] 3. The present invention performs a two-stage homogenization heat treatment on the as-cast billet before rolling, which can effectively eliminate the internal stress in the as-cast billet, improve the grain structure of the aluminum alloy, and lay the foundation for the subsequent rolling and cooling process.

[0036] 4. The Al-Mg alloy prepared by the present invention has higher strength, hardness and corrosion resistance by regulating its composition, thereby expanding the application prospects of Al-Mg aluminum alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The metallographic structure of the high-strength and high-corrosion-resistant Al-Mg aluminum alloy prepared in Example 1 of the present invention;

[0038] Figure 2 SEM image of the high-strength and high-corrosion-resistant Al-Mg aluminum alloy prepared in Example 1 of the present invention;

[0039] Figure 3 Corrosion resistance test chart of the high-strength and high-corrosion-resistant Al-Mg aluminum alloy prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0040] Unless otherwise specified, the test methods described in the examples of the present invention are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0041] In the embodiment of the present invention, the slag removal is to use a graphite tool to remove the oxidized slag on the surface of the melt.

[0042] In the embodiment of the present invention, the inner wall of the crucible is coated with silicon nitride coating to prevent the alloy from adhering to the crucible.

[0043] In the embodiment of the present invention, the purity of the pure aluminum, pure magnesium and pure iron used is ≥99.98%.

[0044] In the embodiments of the present invention, by limiting the mass fractions of the alloy components to 0.65 ≤ Mn + Mo + Fe + Cr ≤ 1.75, and Mn / Cr > 3, the overall performance of the alloy is ensured while also improving the material's strength and structural stability. By limiting the iron content tolerance in the aluminum alloy to 0.50 wt.%, resistance to intergranular corrosion sensitivity in Al-Mg alloys is achieved.

[0045] Example 1

[0046] A method for preparing a high-strength and high-corrosion-resistant Al-Mg aluminum alloy comprises the following steps:

[0047] (1) Prepare pure aluminum, pure magnesium, pure iron and aluminum-based master alloys (Al-10Mn, Al-10Cr, Al-5Mo) as raw materials and preheat them at 250°C, where Mg accounts for 4.56% of the total mass of all raw materials, Mn accounts for 0.64% of the total mass of all raw materials, Cr accounts for 0.13% of the total mass of all raw materials, Mo accounts for 0.12% of the total mass of all raw materials, Fe accounts for 0.17% of the total mass of all raw materials, and the balance is Al.

[0048] (2) Under argon atmosphere, the pure aluminum obtained in step (1) was placed in a crucible and sent into a melting furnace preheated to 425°C. The temperature was raised to 770°C again and kept warm for 30 minutes. After all the pure aluminum was melted, stirring and slag removal were carried out in time. The stirring speed was 220 r / min and the stirring time was 3 minutes to obtain an aluminum melt.

[0049] (3) Under argon atmosphere, add preheated pure iron, Al-10Mn, Al-10Cr and Al-5Mo to the aluminum melt, keep it at 740℃ for 10 min, stir until it is completely melted, and the stirring speed is 220 r / min for 3 min. Then adjust the furnace temperature to 690℃, add preheated pure magnesium to the melt by bell jar pressing, keep it for 3 min, keep it at 10 min, stir it again, and the stirring speed is 220 r / min for 3 min. After the pure magnesium is melted, add 18 g / m 3 The mixture was degassed with hexachloroethane for 6 min, stirred and skimmed to obtain a melt.

[0050] (4) Under argon atmosphere, the melt was heated to 720 °C again, slag was removed again, and then cast into a water-cooled copper mold. During the casting process, the water pressure of the cooling water was controlled to be 0.20 MPa, and the solidification rate of the melt in the water-cooled copper mold was 300 mm / min to obtain a cast billet.

[0051] (5) The as-cast billet was subjected to a two-stage homogenization heat treatment with the following process parameters: the as-cast billet was kept at 340°C for 8 hours, then heated to 520°C and kept there for 10 hours. The purpose of the bipolar homogenization heat treatment is: in the first stage, the low-temperature treatment is to promote uniform element distribution, refine the secondary phase, and control the amount and morphology of the precipitated phase; in the second stage, the high-temperature treatment is to accelerate the dissolution of coarse precipitated phases (such as β-phase Al3Mg2) and reduce residual stress.

[0052] The heat-treated billet was hot rolled at 450°C in 10 passes, with an initial reduction of 8%, a mid-term reduction of 28%, and a final reduction of 37%, for a total reduction of 73%. After hot rolling, an intermediate heat treatment was performed at 340°C for 25 minutes, followed by cold rolling at room temperature with a reduction of 52%, yielding the cold-deformed alloy. This staged reduction control method improves grain refinement and optimizes the mechanical properties of the material.

[0053] (6) The cold-deformed alloy was kept at 200°C for 3 h for stabilization annealing treatment, and the cooling method was air cooling to obtain a high-strength and high-corrosion-resistant Al-Mg aluminum alloy. The stabilization annealing treatment completed by air cooling can improve the residual stress state of the material and enhance the corrosion resistance.

[0054] The obtained Al-Mg aluminum alloy is specifically a plate with a thickness of 15 mm and a width of 80 mm, wherein the mass fraction of impurities is ≤0.30%, and the mass fraction of a single element in the impurities is ≤0.05%.

[0055] The metallographic structure of the aluminum alloy obtained in Example 1 is as follows: Figure 1 As shown in the figure, the refined grain structure and uniformly distributed second phase particles are shown in the SEM image of the aluminum alloy. Figure 2 As shown in the figure, the specific distribution of each phase in the aluminum alloy is reflected. The aluminum alloy is kept at 125℃ for 168 hours for sensitization treatment and corrosion resistance test. The test diagram is shown in Figure 3 shown.

[0056] Example 2

[0057] A method for preparing a high-strength and high-corrosion-resistant Al-Mg aluminum alloy comprises the following steps:

[0058] (1) Prepare pure aluminum, pure magnesium, pure iron and aluminum-based master alloys (Al-10Mn, Al-10Cr, Al-5Mo) as raw materials and preheat them at 300°C, where Mg accounts for 2.80% of the total mass of all raw materials, Mn accounts for 0.55% of the total mass of all raw materials, Cr accounts for 0.11% of the total mass of all raw materials, Mo accounts for 0.24% of the total mass of all raw materials, Fe accounts for 0.20% of the total mass of all raw materials, and the balance is Al.

[0059] (2) Under argon atmosphere, the pure aluminum obtained in step (1) was placed in a crucible and sent into a melting furnace preheated to 420°C. The temperature was raised to 760°C again and kept warm for 35 minutes. After all the pure aluminum was melted, stirring and slagging were carried out in time. The stirring speed was 230 r / min and the stirring time was 4 minutes to obtain an aluminum melt.

[0060] (3) Under argon atmosphere, preheated pure iron, Al-10Mn, Al-10Cr and Al-5Mo were added to the aluminum melt, kept at 750℃ for 12 min, and stirred until completely melted. The stirring speed was 200 r / min and the stirring time was 3 min. Then the furnace temperature was adjusted to 680℃, and preheated pure magnesium was added to the melt by bell jar pressing. After pressing, it was kept for 4 min, kept warm for 12 min, and stirred again at a stirring speed of 220 r / min and the stirring time was 5 min. After the pure magnesium was melted, 20 g / m 3 The mixture was degassed with hexachloroethane for 8 min, stirred and skimmed to obtain a melt.

[0061] (4) Under argon atmosphere, the melt was heated to 730 °C again, the slag was removed again, and then cast into a water-cooled copper mold. During the casting process, the water pressure of the cooling water was controlled to be 0.10 MPa, and the solidification rate of the melt in the water-cooled copper mold was 200 mm / min to obtain a cast billet.

[0062] (5) The as-cast billet was subjected to a two-stage homogenization heat treatment, and the process parameters were as follows: the as-cast billet was kept at 330 °C for 7 h, then heated to 530 °C and kept at this temperature for 11 h.

[0063] The heat-treated billet was hot rolled at 460°C in 10 passes, with an initial reduction of 10%, a mid-term reduction of 32%, and a final reduction of 31%, for a total reduction of 73%. After hot rolling, the billet underwent an intermediate heat treatment at 330°C for 25 minutes, followed by cold rolling at room temperature with a reduction of 50%, yielding the cold-deformed alloy.

[0064] (6) The cold-deformed alloy was kept at 180°C for 2 h for stabilization annealing treatment, and the cooling method was air cooling to obtain a high-strength and high-corrosion-resistant Al-Mg aluminum alloy.

[0065] The obtained Al-Mg aluminum alloy is specifically a plate with a thickness of 17 mm and a width of 80 mm, wherein the mass fraction of impurities is ≤0.30%, and the mass fraction of a single element in the impurities is ≤0.05%.

[0066] Example 3

[0067] A method for preparing a high-strength and high-corrosion-resistant Al-Mg aluminum alloy comprises the following steps:

[0068] (1) Prepare pure aluminum, pure magnesium, pure iron and aluminum-based master alloys (Al-10Mn, Al-10Cr, Al-5Mo) as raw materials and preheat them at 280°C, where Mg accounts for 4.50% of the total mass of all raw materials, Mn accounts for 0.80% of the total mass of all raw materials, Cr accounts for 0.22% of the total mass of all raw materials, Mo accounts for 0.15% of the total mass of all raw materials, Fe accounts for 0.15% of the total mass of all raw materials, and the balance is Al.

[0069] (2) Under argon atmosphere, the pure aluminum obtained in step (1) was placed in a crucible and sent into a melting furnace preheated to 430°C. The temperature was raised to 780°C again and kept warm for 40 minutes. After all the pure aluminum was melted, stirring and slag removal were carried out in time. The stirring speed was 200 r / min and the stirring time was 5 minutes to obtain an aluminum melt.

[0070] (3) Under argon atmosphere, add preheated pure iron, Al-10Mn, Al-10Cr and Al-5Mo to the aluminum melt, keep it at 760℃ for 15 minutes, and stir until it is completely melted. The stirring speed is 250 r / min and the stirring time is 3 minutes. Then adjust the furnace temperature to 685℃, and add preheated pure magnesium to the melt by bell-shaped pressure injection. Keep it for 3 minutes after pressing, keep it at this temperature for 13 minutes, and stir it again. The stirring speed is 230 r / min and the stirring time is 4 minutes. After the pure magnesium is melted, add 15 g / m 3 The mixture was degassed with hexachloroethane for 10 min, stirred and skimmed to obtain a melt.

[0071] (4) Under argon atmosphere, the melt was heated to 710 °C again, slag was removed again, and then cast into a water-cooled copper mold. During the casting process, the pressure of the cooling water was controlled to be 0.30 MPa, and the solidification rate of the melt in the water-cooled copper mold was 400 mm / min to obtain a cast billet.

[0072] (5) The as-cast billet was subjected to a two-stage homogenization heat treatment, and the process parameters were as follows: the as-cast billet was kept at 300 °C for 9 h, then heated to 540 °C and kept at that temperature for 10 h.

[0073] The heat-treated billet was hot rolled at 440°C in 12 passes, with an initial reduction of 10%, a mid-term reduction of 30%, and a final reduction of 40%, for a total reduction of 80%. After hot rolling, the billet underwent an intermediate heat treatment at 350°C for 30 minutes, followed by cold rolling at room temperature with a reduction of 55%, yielding the cold-deformed alloy.

[0074] (6) The cold-deformed alloy was kept at 280°C for 4 h for stabilization annealing treatment, and the cooling method was air cooling to obtain a high-strength and high-corrosion-resistant Al-Mg aluminum alloy.

[0075] The obtained Al-Mg aluminum alloy is specifically a plate with a thickness of 10 mm and a width of 85 mm, wherein the mass fraction of impurities is ≤0.30%, and the mass fraction of a single element in the impurities is ≤0.05%.

[0076] Example 4

[0077] A method for preparing a high-strength and high-corrosion-resistant Al-Mg aluminum alloy comprises the following steps:

[0078] (1) Prepare pure aluminum, pure magnesium, pure iron and aluminum-based master alloys (Al-10Mn, Al-10Cr, Al-5Mo) as raw materials and preheat them at 350°C, where Mg accounts for 4.74% of the total mass of all raw materials, Mn accounts for 0.80% of the total mass of all raw materials, Cr accounts for 0.24% of the total mass of all raw materials, Mo accounts for 0.24% of the total mass of all raw materials, Fe accounts for 0.20% of the total mass of all raw materials, and the balance is Al.

[0079] (2) Under argon atmosphere, the pure aluminum obtained in step (1) was placed in a crucible and sent into a melting furnace preheated to 440°C. The temperature was raised to 770°C again and kept warm for 40 min. After all the pure aluminum was melted, stirring and slagging were carried out in time. The stirring speed was 250 r / min and the stirring time was 3 min to obtain an aluminum melt.

[0080] (3) Under argon atmosphere, add preheated pure iron, Al-10Mn, Al-10Cr and Al-5Mo to the aluminum melt, keep it at 750℃ for 10 min, stir until it is completely melted, and stir at a speed of 250 r / min for 4 min. Then adjust the furnace temperature to 700℃, add preheated pure magnesium to the melt by bell-shaped pressure, keep it for 3 min, keep it at this temperature for 15 min, stir again, stir at a speed of 250 r / min for 3 min, and add 13 g / m3 of pure magnesium after it is melted. 3 The mixture was degassed with hexachloroethane for 10 min, stirred and skimmed to obtain a melt.

[0081] (4) Under argon atmosphere, the melt was heated to 710 °C again, slag was removed again, and then cast into a water-cooled copper mold. During the casting process, the water pressure of the cooling water was controlled to be 0.25 MPa, and the solidification rate of the melt in the water-cooled copper mold was 410 mm / min to obtain a cast billet.

[0082] (5) The as-cast billet is subjected to a two-stage homogenization heat treatment, and the process parameters are as follows: the as-cast billet is kept at 380°C for 7 hours, then heated to 550°C and kept for 9 hours.

[0083] The heat-treated billet was hot rolled at 430°C in eight passes, with an initial reduction of 7%, a mid-term reduction of 29%, and a final reduction of 34%, for a total reduction of 70%. After hot rolling, an intermediate heat treatment was performed at 300°C for 35 minutes, followed by cold rolling at room temperature with a reduction of 45%, yielding the cold-deformed alloy.

[0084] (6) The cold-deformed alloy was kept at 255°C for 5 h for stabilization annealing treatment, and the cooling method was air cooling to obtain a high-strength and high-corrosion-resistant Al-Mg aluminum alloy.

[0085] The obtained Al-Mg aluminum alloy is specifically a plate with a thickness of 20 mm and a width of 75 mm, wherein the mass fraction of impurities is ≤0.30%, and the mass fraction of a single element in the impurities is ≤0.05%.

[0086] Example 5

[0087] A method for preparing a high-strength and high-corrosion-resistant Al-Mg aluminum alloy comprises the following steps:

[0088] (1) Prepare pure aluminum, pure magnesium, pure iron and aluminum-based master alloys (Al-10Mn, Al-10Cr, Al-5Mo) as raw materials and preheat them at 250°C, where Mg accounts for 2.80% of the total mass of all raw materials, Mn accounts for 0.10% of the total mass of all raw materials, Cr accounts for 0.01% of the total mass of all raw materials, Mo accounts for 0.24% of the total mass of all raw materials, Fe accounts for 0.50% of the total mass of all raw materials, and the balance is Al.

[0089] (2) Under argon atmosphere, the pure aluminum obtained in step (1) was placed in a crucible and sent into a melting furnace preheated to 440°C. The temperature was raised to 780°C again and kept warm for 35 minutes. After all the pure aluminum was melted, stirring and slagging were carried out in time. The stirring speed was 240 r / min and the stirring time was 3 minutes to obtain an aluminum melt.

[0090] (3) Under argon atmosphere, preheated pure iron, Al-10Mn, Al-10Cr and Al-5Mo were added to the aluminum melt, kept at 740℃ for 13 min, and stirred until completely melted. The stirring speed was 180 r / min and the stirring time was 3 min. Then the furnace temperature was adjusted to 680℃, and preheated pure magnesium was added to the melt by bell jar pressing. After pressing, it was kept for 2 min, kept warm for 10 min, and stirred again at a stirring speed of 180 r / min and the stirring time was 3 min. After the pure magnesium was melted, 13 g / m 3 The mixture was degassed with hexachloroethane for 3 min, stirred and skimmed to obtain a melt.

[0091] (4) Under argon atmosphere, the melt was heated to 710 °C again, slag was removed again, and then cast into a water-cooled copper mold. During the casting process, the water pressure of the cooling water was controlled to be 0.08 MPa, and the solidification rate of the melt in the water-cooled copper mold was 180 mm / min to obtain a cast billet.

[0092] (5) The as-cast billet is subjected to a two-stage homogenization heat treatment, and the process parameters are: the as-cast billet is kept at 290°C for 7 hours, then heated to 490°C and kept for 9 hours.

[0093] The heat-treated billet was hot rolled at 420°C in six passes with an initial reduction of 8%, a mid-term reduction of 30%, and a final reduction of 27%, for a total reduction of 65%. After hot rolling, an intermediate heat treatment was performed at 300°C for 15 minutes, followed by cold rolling at room temperature with a reduction of 45%, yielding the cold-deformed alloy.

[0094] (6) The cold-deformed alloy was kept at 90°C for 1 h for stabilization annealing treatment, and the cooling method was air cooling to obtain a high-strength and high-corrosion-resistant Al-Mg aluminum alloy.

[0095] The obtained Al-Mg aluminum alloy is specifically a plate with a thickness of 10 mm and a width of 75 mm, wherein the mass fraction of impurities is ≤0.30%, and the mass fraction of a single element in the impurities is ≤0.05%.

[0096] Example 6

[0097] A method for preparing a high-strength and high-corrosion-resistant Al-Mg aluminum alloy comprises the following steps:

[0098] (1) Prepare pure aluminum, pure magnesium, pure iron and aluminum-based master alloys (Al-10Mn, Al-10Cr, Al-5Mo) as raw materials and preheat them at 250°C, where Mg accounts for 6.00% of the total mass of all raw materials, Mn accounts for 1.40% of the total mass of all raw materials, Cr accounts for 0.14% of the total mass of all raw materials, Mo accounts for 0.01% of the total mass of all raw materials, Fe accounts for 0.20% of the total mass of all raw materials, and the balance is Al.

[0099] (2) Under argon atmosphere, the pure aluminum obtained in step (1) was placed in a crucible and sent into a melting furnace preheated to 450°C. The temperature was raised to 780°C again and kept warm for 40 minutes. After all the pure aluminum was melted, stirring and slagging were carried out in time. The stirring speed was 250 r / min and the stirring time was 5 minutes to obtain an aluminum melt.

[0100] (3) Under argon atmosphere, add preheated pure iron, Al-10Mn, Al-10Cr and Al-5Mo to the aluminum melt, keep it at 760℃ for 15 minutes, and stir until it is completely melted. The stirring speed is 250 r / min and the stirring time is 5 minutes. Then adjust the furnace temperature to 700℃, and add preheated pure magnesium to the melt by bell-shaped pressure injection. Keep it for 4 minutes after pressing, keep it at this temperature for 15 minutes, and stir it again. The stirring speed is 220 r / min and the stirring time is 5 minutes. After the pure magnesium is melted, add 22 g / m 3 The mixture was degassed with hexachloroethane for 10 min, stirred and skimmed to obtain a melt.

[0101] (4) Under argon atmosphere, the melt was heated to 730 °C again, slag was removed again, and then cast into a water-cooled copper mold. During the casting process, the water pressure of the cooling water was controlled to be 0.30 MPa, and the solidification rate of the melt in the water-cooled copper mold was 420 mm / min to obtain a cast billet.

[0102] (5) The as-cast billet was subjected to a two-stage homogenization heat treatment, and the process parameters were as follows: the as-cast billet was kept at 380°C for 9 h, then heated to 560°C and kept at this temperature for 11 h.

[0103] The heat-treated billet was hot rolled at 470°C in 15 passes, with an initial reduction of 10%, a mid-term reduction of 32%, and a final reduction of 40%, for a total reduction of 82%. After hot rolling, the billet underwent an intermediate heat treatment at 370°C for 35 minutes, followed by cold rolling at room temperature with a reduction of 60%, yielding the cold-deformed alloy.

[0104] (6) The cold-deformed alloy was kept at 300°C for 5 h for stabilization annealing treatment, and the cooling method was air cooling to obtain a high-strength and high-corrosion-resistant Al-Mg aluminum alloy.

[0105] The obtained Al-Mg aluminum alloy is specifically a plate with a thickness of 20 mm and a width of 85 mm, wherein the mass fraction of impurities is ≤0.30%, and the mass fraction of a single element in the impurities is ≤0.05%.

[0106] Example 7

[0107] A method for preparing a high-strength and high-corrosion-resistant Al-Mg aluminum alloy comprises the following steps:

[0108] (1) Prepare pure aluminum, pure magnesium, pure iron and aluminum-based master alloys (Al-10Mn, Al-10Cr, Al-5Mo) as raw materials and preheat them at 250°C, where Mg accounts for 2.80% of the total mass of all raw materials, Mn accounts for 0.63% of the total mass of all raw materials, Cr accounts for 0.01% of the total mass of all raw materials, Mo accounts for 0.01% of the total mass of all raw materials, and the balance is Al.

[0109] (2) Under argon atmosphere, the pure aluminum obtained in step (1) was placed in a crucible and sent into a melting furnace preheated to 400°C. The temperature was raised to 760°C again and kept warm for 30 minutes. After all the pure aluminum was melted, stirring and slag removal were carried out in time. The stirring speed was 220 r / min and the stirring time was 4 minutes to obtain an aluminum melt.

[0110] (3) Under argon atmosphere, add preheated pure iron, Al-10Mn, Al-10Cr and Al-5Mo to the aluminum melt, keep it at 740℃ for 12 minutes, and stir until it is completely melted. The stirring speed is 180 r / min and the stirring time is 3 minutes. Then adjust the furnace temperature to 680℃, and add preheated pure magnesium to the melt by bell-shaped pressure injection. Keep it for 3 minutes after pressing, keep it at this temperature for 10 minutes, and stir it again at a stirring speed of 220 r / min and the stirring time is 3 minutes. After the pure magnesium is melted, add 18 g / m 3 The mixture was degassed with hexachloroethane for 6 min, stirred and skimmed to obtain a melt.

[0111] (4) Under argon atmosphere, the melt was heated to 720 °C again, slag was removed again, and then cast into a water-cooled copper mold. During the casting process, the water pressure of the cooling water was controlled to be 0.20 MPa, and the solidification rate of the melt in the water-cooled copper mold was 300 mm / min to obtain a cast billet.

[0112] (5) The as-cast billet is subjected to a two-stage homogenization heat treatment, and the process parameters are as follows: the as-cast billet is kept at 340°C for 8 h, then heated to 520°C and kept at this temperature for 10 h.

[0113] The heat-treated billet was hot rolled at 440°C in 10 passes, with an initial reduction of 10%, a mid-term reduction of 25%, and a final reduction of 38%, for a total reduction of 73%. After hot rolling, the billet underwent an intermediate heat treatment at 340°C for 25 minutes, followed by cold rolling at room temperature with a reduction of 55%, yielding the cold-deformed alloy.

[0114] (6) The cold-deformed alloy was kept at 180°C for 4 h for stabilization annealing treatment, and the cooling method was air cooling to obtain a high-strength and high-corrosion-resistant Al-Mg aluminum alloy.

[0115] The obtained Al-Mg aluminum alloy is specifically a plate with a thickness of 15 mm and a width of 80 mm, wherein the mass fraction of impurities is ≤0.30%, and the mass fraction of a single element in the impurities is ≤0.05%.

[0116] Comparative Example 1

[0117] A method for preparing an Al-Mg series aluminum alloy comprises the following steps:

[0118] (1) Prepare pure aluminum, pure magnesium, pure iron and aluminum-based master alloy Al-10Mn as raw materials and preheat them at 250°C, where Mg accounts for 4.56% of the total mass of all raw materials, Mn accounts for 0.64% of the total mass of all raw materials, Fe accounts for 0.17% of the total mass of all raw materials, and the balance is Al.

[0119] (2) Under argon atmosphere, the pure aluminum obtained in step (1) was placed in a crucible and sent into a melting furnace preheated to 425°C. The temperature was raised to 770°C again and kept warm for 30 minutes. After all the pure aluminum was melted, stirring and slag removal were carried out in time. The stirring speed was 220 r / min and the stirring time was 3 minutes to obtain an aluminum melt.

[0120] (3) Under argon atmosphere, add preheated pure iron and Al-10Mn to the aluminum melt, keep it at 740℃ for 10 min, stir until it is completely melted, the stirring speed is 220 r / min, and the stirring time is 3 min. Then adjust the furnace temperature to 690℃, add preheated pure magnesium to the melt by bell jar pressing, keep it for 3 min, keep it at 10 min, stir it again, the stirring speed is 220 r / min, and the stirring time is 3 min. After the pure magnesium is melted, add 18 g / m 3 The mixture was degassed with hexachloroethane for 6 min, stirred and skimmed to obtain a melt.

[0121] (4) Under argon atmosphere, the melt was heated to 720 °C again, slag was removed again, and then cast into a water-cooled copper mold. During the casting process, the water pressure of the cooling water was controlled to be 0.20 MPa, and the solidification rate of the melt in the water-cooled copper mold was 300 mm / min to obtain a cast billet.

[0122] (5) The as-cast billet is subjected to a two-stage homogenization heat treatment, and the process parameters are as follows: the as-cast billet is kept at 340°C for 8 h, then heated to 520°C and kept at this temperature for 10 h.

[0123] The heat-treated billet was hot rolled at 450°C in 10 passes, with an initial reduction of 8%, a mid-term reduction of 28%, and a final reduction of 37%, for a total reduction of 73%. After hot rolling, the billet underwent an intermediate heat treatment at 340°C for 25 minutes, followed by cold rolling at room temperature with a reduction of 52%, yielding the cold-deformed alloy.

[0124] (6) The cold-deformed alloy was kept at 200°C for 3 h for stabilization annealing treatment. The cooling method was air cooling to obtain an Al-Mg aluminum alloy, specifically a plate with a thickness of 15 mm and a width of 80 mm.

[0125] By comparison, the Mo and Cr elements added in Example 1 effectively reduced intergranular corrosion and further improved the corrosion resistance, while Comparative Example 1 did not add these two elements, so its corrosion quality loss was greater.

[0126] Comparative Example 2

[0127] A method for preparing an Al-Mg series aluminum alloy comprises the following steps:

[0128] (1) Prepare pure aluminum, pure magnesium, pure iron and aluminum-based master alloys (Al-10Mn, Al-10Cr) as raw materials and preheat them at 250°C, where Mg accounts for 4.56% of the total mass of all raw materials, Mn accounts for 0.64% of the total mass of all raw materials, Cr accounts for 0.13% of the total mass of all raw materials, Fe accounts for 0.17% of the total mass of all raw materials, and the balance is Al.

[0129] (2) Under argon atmosphere, the pure aluminum obtained in step (1) was placed in a crucible and sent into a melting furnace preheated to 425°C. The temperature was raised to 770°C again and kept warm for 30 minutes. After all the pure aluminum was melted, stirring and slag removal were carried out in time. The stirring speed was 220 r / min and the stirring time was 3 minutes to obtain an aluminum melt.

[0130] (3) Under argon atmosphere, add preheated pure iron, Al-10Mn and Al-10Cr to the aluminum melt, keep it at 740℃ for 10 minutes, and stir until it is completely melted. The stirring speed is 220 r / min and the stirring time is 3 minutes. Then adjust the furnace temperature to 690℃, add preheated pure magnesium to the melt by bell-shaped pressure, keep it for 3 minutes after pressing, keep it at 10 minutes, and stir it again. The stirring speed is 220 r / min and the stirring time is 3 minutes. After the pure magnesium is melted, add 18g / m 3 The mixture was degassed with hexachloroethane for 6 min, stirred and skimmed to obtain a melt.

[0131] (4) Under argon atmosphere, the melt was heated to 720 °C again, slag was removed again, and then cast into a water-cooled copper mold. During the casting process, the water pressure of the cooling water was controlled to be 0.20 MPa, and the solidification rate of the melt in the water-cooled copper mold was 300 mm / min to obtain a cast billet.

[0132] (5) The as-cast billet is subjected to a two-stage homogenization heat treatment, and the process parameters are as follows: the as-cast billet is kept at 340°C for 8 h, then heated to 520°C and kept at this temperature for 10 h.

[0133] The heat-treated billet was hot rolled at 450°C in 10 passes, with an initial reduction of 8%, a mid-term reduction of 28%, and a final reduction of 37%, for a total reduction of 73%. After hot rolling, the billet underwent an intermediate heat treatment at 340°C for 25 minutes, followed by cold rolling at room temperature with a reduction of 52%, yielding the cold-deformed alloy.

[0134] (6) The cold-deformed alloy was kept at 200°C for 3 h for stabilization annealing treatment. The cooling method was air cooling to obtain an Al-Mg aluminum alloy, specifically a plate with a thickness of 15 mm and a width of 80 mm.

[0135] By comparison, the Mo and Cr elements added in Example 1 effectively reduced intergranular corrosion and further improved the corrosion resistance, while the Mo element was not added in Comparative Example 2, so it was easy to precipitate continuous grain boundary β phase, the dispersed phase was unevenly distributed, the corrosion resistance was poor, and the mechanical properties were limitedly improved, which made it difficult to meet the requirements of high-performance applications.

[0136] Comparative Example 3

[0137] A method for preparing an Al-Mg series aluminum alloy comprises the following steps:

[0138] (1) Prepare pure aluminum, pure magnesium, pure iron and aluminum-based master alloy (Al-10Mn, Al-10Cr) as raw materials and preheat them at 250°C, where Mg accounts for 4.56% of the total mass of all raw materials, Mn accounts for 0.64% of the total mass of all raw materials, Mo accounts for 0.12% of the total mass of all raw materials, Fe accounts for 0.17% of the total mass of all raw materials, and the balance is Al.

[0139] (2) Under argon atmosphere, the pure aluminum obtained in step (1) was placed in a crucible and sent into a melting furnace preheated to 425°C. The temperature was raised to 770°C again and kept warm for 30 minutes. After all the pure aluminum was melted, stirring and slag removal were carried out in time. The stirring speed was 220 r / min and the stirring time was 3 minutes to obtain an aluminum melt.

[0140] (3) Under argon atmosphere, add preheated pure iron, Al-10Mn and Al-5Mo to the aluminum melt, keep it at 740℃ for 10 minutes, stir until it is completely melted, and the stirring speed is 220 r / min for 3 minutes. Then adjust the furnace temperature to 690℃, add preheated pure magnesium to the melt by bell-shaped pressure, keep it for 3 minutes, keep it at this temperature for 10 minutes, stir it again, and the stirring speed is 220 r / min for 3 minutes. After the pure magnesium is melted, add 18g / m 3 The mixture was degassed with hexachloroethane for 6 min, stirred and skimmed to obtain a melt.

[0141] (4) Under argon atmosphere, the melt was heated to 720 °C again, slag was removed again, and then cast into a water-cooled copper mold. During the casting process, the water pressure of the cooling water was controlled to be 0.20 MPa, and the solidification rate of the melt in the water-cooled copper mold was 300 mm / min to obtain a cast billet.

[0142] (5) The as-cast billet is subjected to a two-stage homogenization heat treatment, and the process parameters are as follows: the as-cast billet is kept at 340°C for 8 h, then heated to 520°C and kept at this temperature for 10 h.

[0143] The heat-treated billet was hot rolled at 450°C in 10 passes, with an initial reduction of 8%, a mid-term reduction of 28%, and a final reduction of 37%, for a total reduction of 73%. After hot rolling, the billet underwent an intermediate heat treatment at 340°C for 25 minutes, followed by cold rolling at room temperature with a reduction of 52%, yielding the cold-deformed alloy.

[0144] (6) The cold-deformed alloy was kept at 200°C for 3 h for stabilization annealing treatment. The cooling method was air cooling to obtain an Al-Mg aluminum alloy, specifically a plate with a thickness of 15 mm and a width of 80 mm.

[0145] By comparison, the Mo and Cr elements added in Example 1 effectively reduced intergranular corrosion and further improved the corrosion resistance, while in Comparative Example 3, no Cr element was added, so the precipitation of β phase at the grain boundary increased, the density of the oxide film decreased, and the corrosion resistance decreased.

[0146] The mechanical properties of the Al-Mg aluminum alloys obtained in Examples 1-7 and Comparative Examples 1-3 are shown in Table 1.

[0147] Table 1 Mechanical properties of Al-Mg aluminum alloys obtained in Examples 1-7 and Comparative Examples 1-3

[0148]

[0149] The present invention has been described in detail above. The description of the specific embodiments is intended only to facilitate understanding of the method and core concept of the present invention. It should be noted that those skilled in the art may make various improvements and modifications to the present invention without departing from the principles of the present invention, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A high-strength and high-corrosion-resistant Al-Mg aluminum alloy, characterized in that: Its chemical composition, calculated by mass percentage, includes: Mg 2.80%~6.00%, Mn 0.10%~1.40%, Cr 0.01%~0.24%, Mo 0.01%~0.24%, Fe 0.00%~0.50%, and the remainder is Al, and must also meet 0.65≤Mn+Mo+Fe+Cr≤1.75, and Mn / Cr>3; The mass fraction of impurities in the high-strength and high-corrosion-resistant Al-Mg aluminum alloy is ≤0.30%, and the mass fraction of a single element in the impurities is ≤0.05%; The high-strength and high-corrosion-resistant Al-Mg aluminum alloy has a yield strength of 370 MPa to 400 MPa, a tensile strength of 230 MPa to 268 MPa, an elongation of 14% to 18%, and a corrosion mass loss of 17 mg cm -2 ~37 mg cm -2 .

2. The method for preparing a high-strength and high-corrosion-resistant Al-Mg aluminum alloy according to claim 1, characterized in that: The specific steps include: (1) Preheat pure aluminum, pure magnesium, pure iron and aluminum-based master alloy for standby use; (2) Under protective atmosphere conditions, the pure aluminum obtained in step (1) is added to a preheated smelting furnace and the temperature is raised again. After all the pure aluminum is melted, stirring and slag removal are carried out in a timely manner to obtain an aluminum melt; (3) Under protective atmosphere conditions, preheated pure iron and aluminum-based master alloy are added to the aluminum melt and stirred until completely melted. Preheated pure magnesium is added to the resulting melt and stirred again. After the pure magnesium is melted, hexachloroethane is added for degassing, and the mixture is stirred and skimmed to obtain a melt; (4) Under protective atmosphere conditions, the melt is heated again, the slag is removed again, and then cast into a water-cooled copper mold to obtain a cast billet; (5) subjecting the as-cast billet to a two-stage homogenization heat treatment, followed by hot rolling and cold rolling in sequence to obtain a cold-deformed alloy; (6) The cold-deformed alloy is subjected to stabilization annealing treatment to obtain a high-strength and high-corrosion-resistant Al-Mg aluminum alloy.

3. The method for preparing a high-strength and high-corrosion-resistant Al-Mg aluminum alloy according to claim 2, characterized in that: In the step (1), the purity of pure aluminum, pure magnesium and pure iron is ≥99.98%, the aluminum-based master alloy is specifically Al-10Mn, Al-10Cr and Al-5Mo, and the preheating temperature is 150°C to 350°C.

4. The method for preparing a high-strength and high-corrosion-resistant Al-Mg aluminum alloy according to claim 2, characterized in that: In the step (2), the preheating temperature of the smelting furnace is 400°C to 450°C, the smelting temperature of pure aluminum is 760°C to 780°C, and the holding time is 30 min to 40 min.

5. The method for preparing a high-strength and high-corrosion-resistant Al-Mg aluminum alloy according to claim 2, characterized in that: In step (3), the melting temperature of pure iron and aluminum-based master alloy is 740°C to 760°C, and the holding time is 10 min to 15 min; The pure magnesium is added to the melt by pressing it into a bell jar and kept for 2 to 4 minutes after pressing. The melting temperature of the pure magnesium is 680 to 700 degrees Celsius and the holding time is 10 to 15 minutes. The amount of hexachloroethane added is 13 g / m 3 ~22 g / m 3 , the degassing time is 3 min~10 min.

6. The method for preparing a high-strength and high-corrosion-resistant Al-Mg aluminum alloy according to claim 2, characterized in that: In steps (2) and (3), the stirring speed is 180 r / min to 250 r / min, and the stirring time is 3 min to 5 min; In the steps (2) to (4), the protective atmosphere is argon.

7. The method for preparing a high-strength and high-corrosion-resistant Al-Mg aluminum alloy according to claim 2, characterized in that: In the step (4), the melt is heated to 710°C to 730°C, and then slag is removed again; During the casting process, the water pressure of the cooling water is controlled to be 0.08 MPa to 0.30 MPa, and the solidification speed of the molten liquid in the water-cooled copper mold is 180 mm / min to 420 mm / min.

8. The method for preparing a high-strength and high-corrosion-resistant Al-Mg aluminum alloy according to claim 2, characterized in that: In step (5), the double-stage homogenization heat treatment is specifically as follows: the as-cast billet is kept at 290°C to 380°C for 7 h to 9 h, then the temperature is raised to 490°C to 560°C and kept at this temperature for 9 h to 11 h; The hot rolling and cold rolling processes are as follows: hot rolling the as-cast billet at a temperature of 420° C. to 470° C. with a reduction of 65% to 82%, performing an intermediate heat treatment at 300° C. to 370° C. after hot rolling, holding the temperature for 15 min to 35 min, and then cold rolling at room temperature with a reduction of 45% to 60%; The hot rolling deformation process is divided into 6 to 15 passes, with an initial reduction rate of 5% to 10%, a mid-term reduction rate of 15% to 32%, and a late reduction rate of 25% to 40%.

9. The method for preparing a high-strength and high-corrosion-resistant Al-Mg aluminum alloy according to claim 2, characterized in that: In the step (6), the stabilization annealing treatment is specifically as follows: the alloy after cold deformation is kept at a temperature of 90°C to 300°C for 1 hour to 5 hours, and the cooling method is air cooling.

10. The method for preparing a high-strength and high-corrosion-resistant Al-Mg aluminum alloy according to claim 2, characterized in that: In the step (6), the high-strength and high-corrosion-resistant Al-Mg aluminum alloy is specifically a plate with a thickness of 10 mm to 20 mm and a width of 75 mm to 85 mm.

Images