Heat-treatment-free self-strengthening Al-Mg aluminum alloy and preparation method thereof

Abstract

The invention discloses a heat-treatment-free self-strengthening Al-Mg aluminum alloy and a preparation method thereof, and relates to the technical field of aluminum alloy materials, and the heat-treatment-free self-strengthening Al-Mg aluminum alloy comprises the following chemical components in percentage by mass: 4.35%-5.63% of Mg, 0.23%-2.10% of Si, 0.41%-1.46% of Zn, 0.35%-2.00% of Cu, 0.05%-0.50% of Mo, 0.01%-0.41% of Fe and the balance of Al. Through the optimized smelting, modification treatment and heating treatment processes, the alloy can obtain excellent mechanical properties and structure stability in a cast state, and the limitation that traditional aluminum alloy depends on heat treatment strengthening is avoided. The preparation method has the advantages of being easy and convenient to operate, low in cost and the like, and the prepared aluminum alloy is suitable for light-weight requirement scenes such as automobile structural parts, chassis and power systems.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy materials, and particularly relates to a heat-treatment-free self-strengthening Al-Mg aluminum alloy and a preparation method thereof. Background Art

[0002] Research shows that vehicle fuel consumption and CO2 emissions are closely related to vehicle body mass, and weight reduction has become an important path for the automotive industry to achieve energy conservation and emission reduction. To achieve vehicle body lightweighting, aluminum alloy materials are gradually replacing traditional steel materials due to their low density, good weldability, excellent corrosion resistance, and good mechanical properties, and have become the preferred materials for key components in vehicle body structures and powertrains.

[0003] Cast aluminum alloys are widely used in the automotive field due to their good fluidity, formability, thermal conductivity, strength, and cost advantages. Among them, the integrated die-casting process has become an important direction for automotive lightweight manufacturing due to its advantages such as structural integration, reduction in the number of components, and improvement in production efficiency. However, traditional die-casting aluminum alloys such as ADC12 and A380 have problems of insufficient strength and toughness, and usually require subsequent heat treatment to meet the service performance, and are prone to deformation during the heat treatment process, which limits their application in integrated die-casting. Therefore, the development of heat-treatment-free cast aluminum alloys with excellent casting performance and mechanical properties has become the focus of industry research.

[0004] The cast aluminum alloys widely used in the current market are mainly divided into three categories: Al-Si series, Al-Cu series, and Al-Mg series. Although Al-Cu series alloys have relatively high strength, they have poor casting performance and are prone to defects such as hot cracking, which limits their large-scale application; Al-Si series alloys have good casting performance, but lack an effective age hardening mechanism and are difficult to achieve high strength and high toughness; in contrast, Al-Mg series alloys can obtain relatively high strength and toughness because Mg forms a strong solid solution in the matrix, and have become a research hotspot in recent years.

[0005] Typically, the Magsimal-Plus alloy developed by Rheinmetall in Germany has a as-cast tensile strength of about 342 MPa, a yield strength of about 206 MPa, and an elongation of 10.9%. The self-strengthening heat-treatment-free Al-Mg alloy developed by Shanghai Jiao Tong University also exhibits excellent comprehensive performance. However, Al-Mg series alloys generally have defects such as poor castability, large hot cracking tendency, and insufficient melt fluidity, which restrict their further promotion in the die-casting field.

[0006] Existing research shows that adding an appropriate amount of Si element to Al-Mg alloys can not only significantly improve the melt fluidity, enhance the casting performance, but also effectively inhibit brittleness βThe formation of the -Al3Mg2 phase enhances the structural stability of the material. On this basis, introducing transition elements through microalloying for further strengthening has become an effective strategy. In recent years, due to its excellent strengthening potential and regulatory flexibility, the Al-Mg-Zn-Cu alloy has become an important direction for developing high-strength and tough cast aluminum alloys. The Zn element can promote the precipitation of η-MgZn2 or T-Mg 32 (Al,Zn,Cu) 49 phase, resulting in a significant age hardening effect. Especially when the Zn / Mg mass ratio is reasonably regulated, excellent mechanical properties can be obtained. However, adding Zn alone has limited effect on strength improvement and may affect the casting performance.

[0007] As a traditional strengthening element in aluminum alloys, copper has the dual effects of solid solution strengthening and precipitation strengthening. Research shows that the Cu element can accelerate the aging process, stabilize the nucleation of the precipitate phase, and increase the peak strength. However, there is still a lack of systematic research on the synergistic effect of Cu and Zn in Al-Mg-Si cast alloys. Especially, there is still a lack of clear theoretical guidance on how to achieve high-strength alloy design by regulating the content of Cu and Zn while maintaining good toughness. Summary of the Invention

[0008] Based on this, the present invention provides a heat-treatment-free self-strengthening Al-Mg aluminum alloy and its preparation method. The present invention uses the Magsimal-Plus alloy as the matrix, adds a certain amount of Mo element, systematically regulates the content of Cu and Zn, and prepares an Al-Mg-Si-Mo-Cu-Zn series alloy while keeping the content of Mg and Si within a certain range. Through a unified heat treatment process and combined with optical microscopy, scanning electron microscopy, and transmission electron microscopy techniques, the effects of different contents of Cu and Zn on the microstructure evolution and mechanical properties of the alloy in the as-cast state and T6 state are systematically analyzed, and the strengthening mechanism of the synergistic effect of Cu and Zn is revealed, providing a theoretical basis and technical support for developing high-strength, high-toughness, and excellent-casting-performance aluminum alloy materials.

[0009] For the heat-treatment-free self-strengthening Al-Mg aluminum alloy of the present invention, its chemical composition by mass percentage is: Mg: 4.35% - 5.63%, Si: 0.23% - 2.10%, Zn: 0.41% - 1.46%, Cu: 0.35% - 2.00%, Mo: 0.05% - 0.50%, Fe: 0.01% - 0.41%, and the balance is Al. And it satisfies the following relationships: 0% ≤ Si + Zn + Cu + Mo + Fe ≤ 7.0%; 5.0% ≤ Mg + 0.5(Si + Zn + Cu) + 0.3Mo + 0.2Fe ≤ 8.0%.

[0010] The Cu content tolerance is 2.00 wt.%, and its function is to maintain the corrosion resistance of the alloy.

[0011] A preparation method of a heat-treatment-free self-strengthening Al-Mg aluminum alloy of the present invention comprises the following steps: Step 1: Pure aluminum, pure magnesium ingots, pure zinc ingots, pure copper ingots, and intermediate alloys Al-Si, Al-Fe, and Al-5Mo are preheated at 180°C to 240°C in advance for standby; wherein Mg accounts for 4.35% to 5.63% of the total mass of all raw materials, Si accounts for 0.23% to 2.10% of the total mass of all raw materials, Zn accounts for 0.41% to 1.46% of the total mass of all raw materials, Cu accounts for 0.35% to 2.00% of the total mass of all raw materials, Mo accounts for 0.05% to 0.50% of the total mass of all raw materials, Fe accounts for 0.01% to 0.41% of the total mass of all raw materials, and the balance is Al; Step 2: Under the condition of a protective atmosphere, place the crucible in a resistance furnace and heat it. When the temperature is adjusted to 410°C to 460°C, add the preheated pure aluminum. Step 3: Under the condition of a protective atmosphere, adjust the temperature of the resistance furnace to 700°C to 760°C, keep it warm for 25 min to 40 min. After all the pure aluminum is melted, stir and skim the slag in time. Step 4: Under the condition of a protective atmosphere, add pure copper ingots, intermediate alloys Al-Si, Al-Fe, and Al-5Mo in sequence. After they are melted, keep it warm for 10 min to 15 min. When it reaches 740°C to 760°C, add pure magnesium ingots and pure zinc ingots until they are molten. Stir until completely melted, and then keep it warm for 10 min to 25 min. Step 5: Under the condition of a protective atmosphere, add a refiner to the alloy liquid, stir, and skim the slag after standing. Step 6: Under the condition of a protective atmosphere, use hexachloroethane for degassing, and stir and skim the slag. Step 7: Under the condition of a protective atmosphere, skim the slag. The temperature is 700°C to 735°C, and then pour the melt into a water-cooled mold to obtain a as-cast blank. Step 8: The cast aluminum alloy ingot is first subjected to modification treatment and finally heat treatment to obtain a heat-treatment-free self-strengthening Al-Mg aluminum alloy.

[0012] In the steps 2 - 7, the protective atmosphere is an argon atmosphere, and the gas flow rate is 1 L / min to 3 L / min.

[0013] In the steps 3 - 4, the stirring speed is controlled at 200 to 250 revolutions per minute, and the stirring time is 2 min to 6 min to ensure uniform mixing of all alloy elements.

[0014] In the step 4, the pure magnesium ingot is added to the melt in a manner of being pressed in by a bell jar and kept for 2 min to 5 min after pressing in.

[0015] In the said step 4, the addition order of Mo element takes precedence over that of Mg element, which can ensure the full dissolution of Mo in the aluminum matrix and promote the formation of fine and dispersed strengthening phases. The content of Mo is preferably controlled within the range of 0.05 - 0.5 wt.%, so as to effectively promote the precipitation of strengthening phases during the heat treatment process, and improve the strength, toughness and corrosion resistance of the material.

[0016] In the said step 5, under the condition of protective atmosphere, the temperature of the resistance furnace is adjusted to 700°C - 750°C, a refiner is added to the alloy liquid, stirred for 5 min - 10 min, and skimmed after standing for 15 min - 20 min.

[0017] In the said step 5, the refiner used is an Al5TiB metal rod, and the addition amount of the refiner is 0.4% - 0.45% of the melt mass.

[0018] In the said step 6, under the condition of protective atmosphere, the temperature of the resistance furnace is adjusted to 720°C - 745°C, stirred and kept warm for 10 min - 15 min, degassed with hexachloroethane, the addition amount of hexachloroethane powder is 0.65% - 1.0% of the melt mass, and the degassing time is 5 min - 8 min.

[0019] In the said steps 5 - 7, skimming refers to removing the oxidized floating slag on the surface of the melt with a graphite tool.

[0020] In the said step 7, the as-cast billet is processed into a plate, with a length of 190 mm - 210 mm, a width of 90 mm - 110 mm, and a thickness of 25 mm - 35 mm.

[0021] In the said step 7, the melt in the crucible is poured into a water-cooled mold, and the solidification rate of the material in the water-cooled mold is controlled by the cooling water flow rate to be 180 mm / min - 480 mm / min. The material of the water-cooled mold is preferably copper. When casting, the water pressure of the cooling water introduced into the water-cooled mold is 0.10 MPa - 0.40 MPa. The water flow rate introduced into the water-cooled mold is 1.5 m / s - 3 m / s, and the water temperature is controlled within the range of 15°C - 35°C, preferably 25°C.

[0022] In the said step 8, the modification treatment process is: the temperature is 450°C - 500°C, keep warm for 5 h - 10 h, and cool by water quenching. The purpose of the modification treatment is to promote the full dissolution of the second phase through high-temperature heat preservation, realize the homogenization and grain refinement of the as-cast structure, effectively release the residual stress, reduce the corrosion sensitivity, and thus improve the comprehensive mechanical properties and casting quality of the aluminum alloy.

[0023] In the step 8, the heat treatment process is as follows: the temperature is 140°C to 180°C, the heat preservation time is 15h to 25h, and the cooling method is air cooling. The purpose of the heat treatment is to promote the precipitation of dispersion strengthening phases of strengthening elements such as Mg, Si, Cu, and Zn under medium temperature conditions, enhance the matrix strengthening effect, further improve the strength and toughness of the alloy, stabilize the microstructure, improve the corrosion resistance, and realize the stable exertion of self-strengthening performance.

[0024] Through the optimized melting, modification treatment and heat treatment processes, the alloy can obtain excellent mechanical properties and tissue stability in the as-cast state, avoiding the limitations of traditional aluminum alloys relying on heat treatment strengthening. The prepared aluminum alloy has a yield strength of 275MPa to 384MPa, a tensile strength of 178MPa to 286MPa, and an elongation of 6.82% to 11.23% under the condition of not undergoing complex heat treatments (such as solution treatment, homogenization treatment, quenching and aging treatment, etc.), showing a good balance of strength and toughness.

[0025] The innovation of the present invention lies in: through the precise regulation of the contents of Cu and Zn, promoting the orderly precipitation of Cu-rich second phases (θ-Al2Cu and Q-Al5Cu2Mg8Si6) during solidification, optimizing the morphology, size and spatial distribution of the second phases, thereby improving the tissue stability and mechanical properties of the alloy. At the same time, by utilizing the high diffusion characteristics of Zn, effectively weakening the local segregation behavior of Cu during solidification, inhibiting the formation of large-sized Cu-rich phases, significantly improving the tissue uniformity, reducing the hot cracking tendency during casting, and enhancing the plasticity and processing reliability of the material.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) By introducing elements such as Mg, Si, and Cu, forming strengthening phases such as Mg2Si, S-AlMgSiCu, and Q-Al5Cu2Mg8Si6, a multi-element synergistic strengthening mechanism is realized, and the mechanical properties such as the strength and hardness of the alloy are significantly improved without the need for complex heat treatment.

[0027] (2) By adding Fe element, the problem of sticking to the mold during die casting is effectively alleviated, the service life of the mold and the quality of casting forming are improved; the introduction of Mo element effectively improves the tissue stability of the alloy without damaging the plasticity.

[0028] (3) Through alloy composition regulation and control of process parameters such as reasonable melting, degassing, and refinement, sub-micron dispersion strengthening phases are formed in the alloy crystals, endowing the alloy with excellent tensile strengthening and yield strengthening characteristics.

[0029] (4) The aluminum alloy preparation method of the present invention has the advantages of simple operation and low cost. The obtained aluminum alloy is suitable for lightweight demand scenarios such as automotive structural parts, chassis, and power systems, and is also applicable to application fields with high requirements for material strength, toughness, and stability such as aviation, having broad industrialization prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a scanning electron microscope image of a heat-treatment-free self-strengthening Al-Mg aluminum alloy in Example 1 of the present invention; Figure 2 It is an EDS diagram of a heat-treatment-free self-strengthening Al-Mg aluminum alloy in Example 1 of the present invention; Figure 3 It is a exfoliation corrosion test diagram of a heat-treatment-free self-strengthening Al-Mg aluminum alloy in Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] In the embodiments of the present invention, unless otherwise specified, the test methods are all conventional methods; the reagents and materials, unless otherwise specified, can be obtained from commercial channels.

[0032] In the embodiments of the present invention, for casting, the materials in the holding furnace are poured into a water-cooled mold, and after casting - modification treatment - heat treatment, a heat-treatment-free self-strengthening Al-Mg aluminum alloy is made.

[0033] In the embodiments 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.

[0034] In the embodiments of the present invention, the protective atmosphere is an argon atmosphere, and the gas flow rate is 1 L / min to 3 L / min.

[0035] In the embodiments of the present invention, the prepared heat-treatment-free self-strengthening Al-Mg aluminum alloy is in the form of a sheet, with a length of 190 mm to 210 mm, a width of 90 mm to 110 mm, and a thickness of 25 mm to 35 mm.

[0036] In the embodiments of the present invention, the modification treatment process is to keep the temperature at 450 °C to 500 °C for 5 h to 10 h.

[0037] In the embodiments of the present invention, the heat treatment process is to keep the temperature at 140 °C to 180 °C for 15 h to 25 h.

[0038] In the embodiments of the present invention, the pure magnesium ingot is added to the melt in a manner of pressing with a bell jar, and after pressing, it is kept for 2 min to 5 min.

[0039] In the embodiment of the present invention, the solidification rate of the material in the water-cooled copper mold is controlled between 180 mm / min and 480 mm / min by the flow rate of the cooling water. When casting, the water pressure of the cooling water introduced into the water-cooled copper mold is 0.10 MPa to 0.40 MPa. The water flow rate into the water-cooled copper mold is 1.5 m / s to 3 m / s, and the water temperature is controlled at 25 °C.

[0040] Example 1 A preparation method of a heat-treatment-free self-strengthening Al-Mg aluminum alloy, the specific steps are as follows: Step 1: Prepare pure aluminum, pure magnesium ingots, pure zinc ingots, pure copper ingots, and intermediate alloys Al-Si, Al-Fe, and Al-5Mo as raw materials; among them, Mg accounts for 4.88% of the total mass of all raw materials, Si accounts for 1.88% of the total mass of all raw materials, Zn accounts for 1.33% of the total mass of all raw materials, Cu accounts for 1.40% of the total mass of all raw materials, Mo accounts for 0.22% of the total mass of all raw materials, Fe accounts for 0.04% of the total mass of all raw materials, and the balance is Al; The purity of pure aluminum ≥ 99.98%, the purity of pure magnesium ≥ 99.98%, the purity of pure zinc ≥ 99.98%, and the purity of pure copper ≥ 99.98%; Step 2: Under the condition of an argon atmosphere, place the crucible in an electric resistance furnace for preheating, and the preheating temperature is set at 410 °C to 460 °C; Step 3: Under the condition of an argon atmosphere, place pure aluminum in the crucible, adjust the temperature to 745 °C, and hold for 25 min to form an aluminum melt; after all the pure aluminum is melted, stir and skim the slag in time; the stirring speed is controlled at 200 revolutions per minute, and the stirring time is 3 min; Step 4: Under the condition of an argon atmosphere, add the preheated pure copper ingot, Al-Si, Al-Fe, and Al-5Mo intermediate alloys, and hold at 745 °C for 10 min; Under the condition of an argon atmosphere, adjust the furnace temperature to 740 °C, add the preheated industrial pure magnesium and pure zinc ingots, stir until completely melted and hold for 18 min; the stirring speed is controlled at 200 revolutions per minute, and the stirring time is 3 min; Step 5: Under the condition of an argon atmosphere, adjust the furnace temperature to 700 °C, add the grain refiner Al5TiB metal rod, and the addition amount of the grain refiner is 0.4% of the melt mass, stir for 5 min, let stand for 15 min, and then skim the slag; Step 6: Under the condition of an argon atmosphere, adjust the furnace temperature to 720 °C, stir until completely melted and hold for 10 min, degas with hexachloroethane for 5 min, and the addition amount of hexachloroethane powder is 0.65% of the melt mass. Then take out the crucible, skim the slag at 700 °C, and pour the melt into a water-cooled copper mold to cast a flat ingot; Step 7: Perform modification treatment on the as-cast blank. The specific process conditions are as follows: keep it warm at 460 °C for 5 h and cool it by water quenching; Step 8: Heat-treat the blank after modification treatment. The specific process conditions are as follows: keep it warm at 150 °C for 15 h and cool it by air cooling, and finally prepare a heat-treatable self-strengthening Al-Mg aluminum alloy. The metallographic structure diagram is as Figure 1 shown, Figure 1 which shows the microscopic structure characteristics of the alloy, mainly composed of light-colored α-Al matrix, black intermetallic compounds, and some dark gray intermetallic compounds. The SEM photo of the alloy is as Figure 2 shown. The exfoliation corrosion test results of the alloy at 150 °C - 250 °C for 3 h - 7 h are as Figure 3 shown. The relevant data of the tensile properties of Example 1 of the present invention are shown in Table 1; the yield strength of this heat-treatable self-strengthening Al-Mg aluminum alloy is 286 MPa, the tensile strength is 386 MPa, and the elongation is 7.02%. The fracture of the tensile specimen consists of dimples and tear ridges of uneven sizes, showing obvious plastic fracture characteristics.

[0041] Table 1 Mechanical properties of alloys in Examples 1-9 and Comparative Example 1:

[0042] Comparative Example 1 was experimentally carried out using the method of Example 1. The difference is that Zn, Cu, and Mo were not added, and an Al-Mg-Si alloy was obtained. Its yield strength is 170 MPa, the tensile strength is 270 MPa, and the elongation is 10.02%.

[0043] Example 2 A preparation method of a heat-treatable self-strengthening Al-Mg aluminum alloy, and the specific steps are as follows: Step 1: Prepare pure aluminum, pure magnesium ingots, pure zinc ingots, pure copper ingots, and intermediate alloys Al-Si, Al-Fe, and Al-5Mo as raw materials; among them, Mg accounts for 5.02% of the total mass of all raw materials, Si accounts for 0.88% of the total mass of all raw materials, Zn accounts for 0.45% of the total mass of all raw materials, Cu accounts for 0.46% of the total mass of all raw materials, Mo accounts for 0.05% of the total mass of all raw materials, Fe accounts for 0.02% of the total mass of all raw materials, and the balance is Al; The purity of pure aluminum ≥ 99.98%, the purity of pure magnesium ≥ 99.98%, the purity of pure zinc ≥ 99.98%, and the purity of pure copper ≥ 99.98%; Step 2: Under the condition of argon atmosphere, put the crucible into the resistance furnace for preheating, and set the preheating temperature to 410 °C - 460 °C; Step 3: Under the condition of argon atmosphere, place pure aluminum in a crucible, adjust the temperature to 755 °C, keep it warm for 25 min to form an aluminum melt; stir and skim the slag in time after all the pure aluminum has melted; control the stirring speed at 200 revolutions per minute and the stirring time at 3 min; Step 4: Under the condition of argon atmosphere, add preheated pure copper ingots, Al-Si, Al-Fe and Al-5Mo master alloys, and keep it warm at 748 °C for 10 min; Under the condition of argon atmosphere, adjust the furnace temperature to 750 °C, add preheated industrial pure magnesium and pure zinc ingots, stir until completely melted and then keep it warm for 17 min. Control the stirring speed at 200 revolutions per minute and the stirring time at 3 min; Step 5: Under the condition of argon atmosphere, adjust the furnace temperature to 700 °C, add the grain refiner Al5TiB metal rod, and the addition amount of the grain refiner is 0.45% of the total mass of the melt, stir for 5 min, let it stand for 15 min and then skim the slag; Step 6: Under the condition of argon atmosphere, adjust the furnace temperature to 720 °C, stir until completely melted and keep it warm for 10 min, degas with hexachloroethane for 5 min, and the addition amount of hexachloroethane powder is 1.0% of the mass of the melt. Then take out the crucible, skim the slag at 700 °C, pour the molten liquid into a water-cooled copper mold, and cast the aluminum liquid into a flat ingot; Step 7: Carry out modification treatment on the as-cast blank, and the specific process conditions are: in an environment with a temperature of 460 °C, keep it warm for 6 h, and cool it by water quenching; Step 8: Carry out heat treatment on the modified blank, and the specific process conditions are: in an environment with a temperature of 155 °C, keep it warm for 17 h, and the cooling method is air cooling. Its yield strength is 220 MPa, tensile strength is 275 MPa, and elongation is 6.82%.

[0044] Example 3 A preparation method of a heat-treatable self-strengthening Al-Mg aluminum alloy, the specific steps are as follows: Step 1: Prepare pure aluminum, pure magnesium ingots, pure zinc ingots, pure copper ingots and master alloys Al-Si, Al-Fe and Al-5Mo as raw materials; among them, Mg accounts for 5.36% of the total mass of all raw materials, Si accounts for 0.58% of the total mass of all raw materials, Zn accounts for 0.88% of the total mass of all raw materials, Cu accounts for 0.35% of the total mass of all raw materials, Mo accounts for 0.15% of the total mass of all raw materials, Fe accounts for 0.04% of the total mass of all raw materials, and the balance is Al; The purity of pure aluminum ≥ 99.98%, the purity of pure magnesium ≥ 99.98%, the purity of pure zinc ≥ 99.98%, and the purity of pure copper ≥ 99.98%; Step 2: Under the condition of argon atmosphere, place the crucible in a resistance furnace for preheating, and set the preheating temperature to 410 °C - 460 °C; Step 3: Under the condition of argon atmosphere, place pure aluminum in a crucible, adjust the temperature to 755 °C, and keep it warm for 35 min to form an aluminum melt; after all the pure aluminum has melted, stir and skim the slag in a timely manner; the stirring speed is controlled at 200 revolutions per minute, and the stirring time is 3 min; Step 4: Under the condition of argon atmosphere, add preheated pure copper ingots, Al-Si, Al-Fe and Al-5Mo master alloys, and keep it warm at 748 °C for 15 min; Under the condition of argon atmosphere, adjust the furnace temperature to 750 °C, add preheated industrial pure magnesium and pure zinc ingots, stir until completely melted and keep it warm for 20 min. The stirring speed is controlled at 200 revolutions per minute, and the stirring time is 3 min; Step 5: Under the condition of argon atmosphere, adjust the furnace temperature to 700 °C, add the refining agent Al5TiB metal rod, and the addition amount of the refining agent is 0.45% of the total mass of the melt, stir for 5 min, skim the slag after standing for 20 min; Step 6: Under the condition of argon atmosphere, adjust the furnace temperature to 730 °C, stir until completely melted and keep it warm for 15 min, degas with hexachloroethane for 5 min, and the addition amount of hexachloroethane powder is 0.65% of the mass of the melt. Then take out the crucible, skim the slag at 700 °C, and pour the molten liquid into a water-cooled copper mold to cast the aluminum liquid into a flat ingot; Step 7: Perform modification treatment on the as-cast blank, and the specific process conditions are: in an environment of 450 °C and keep it warm for 8 h, and cool by water quenching; Step 8: Perform heat treatment on the modified blank, and the specific process conditions are: in an environment of 140 °C and keep it warm for 25 h, and the cooling method is air cooling. Its yield strength is 235 MPa, tensile strength is 287 MPa, and elongation is 7.23%.

[0045] Example 4 A preparation method of a heat-treatable self-strengthening Al-Mg aluminum alloy, the specific steps are as follows: Step 1: Prepare pure aluminum, pure magnesium ingots, pure zinc ingots, pure copper ingots and master alloys Al-Si, Al-Fe and Al-5Mo as raw materials; among them, Mg accounts for 5.36% of the total mass of all raw materials, Si accounts for 0.78% of the total mass of all raw materials, Zn accounts for 1.43% of the total mass of all raw materials, Cu accounts for 0.47% of the total mass of all raw materials, Mo accounts for 0.3% of the total mass of all raw materials, Fe accounts for 0.12% of the total mass of all raw materials, and the balance is Al; The purity of pure aluminum ≥ 99.98%, the purity of pure magnesium ≥ 99.98%, the purity of pure zinc ≥ 99.98%, and the purity of pure copper ≥ 99.98%; Step 2: Under the condition of argon atmosphere, put the crucible into the resistance furnace for preheating, and set the preheating temperature to 410°C - 460°C; Step 3: Under the condition of argon atmosphere, place pure aluminum in the crucible, adjust the temperature to 700°C, keep it warm for 40 minutes to form aluminum melt; after all the pure aluminum has melted, stir and skim the slag in time; control the stirring speed at 200 revolutions per minute, and the stirring time is 3 minutes; Step 4: Under the condition of argon atmosphere, add the preheated pure copper ingot, Al - Si, Al - Fe and Al - 5Mo master alloys, and keep it warm at 755°C for 15 minutes; Under the condition of argon atmosphere, adjust the furnace temperature to 760°C, add the pre - heated industrial pure magnesium and pure zinc ingot, stir until completely melted and keep it warm for 10 minutes. Control the stirring speed at 200 revolutions per minute, and the stirring time is 3 minutes; Step 5: Under the condition of argon atmosphere, adjust the furnace temperature to 720°C, add the grain refiner Al5TiB metal rod, and the addition amount of the grain refiner is 0.45% of the total mass of the melt, stir for 5 minutes, let it stand for 15 minutes and then skim the slag; Step 6: Under the condition of argon atmosphere, adjust the furnace temperature to 745°C, stir until completely melted and keep it warm for 10 minutes, degas with hexachloroethane for 5 minutes, and the addition amount of hexachloroethane powder is 0.80% of the mass of the melt. Then take out the crucible, skim the slag at 735°C, and pour the molten liquid into a water - cooled copper mold to cast the aluminum liquid into a flat ingot; Step 7: Carry out modification treatment on the as - cast blank, and the specific process conditions are: in an environment with a temperature of 480°C, and keep it warm for 5 hours, and cool by water quenching; Step 8: Carry out heat treatment on the modified blank, and the specific process conditions are: in an environment with a temperature of 180°C, and keep it warm for 15 hours, and the cooling method is air cooling. Its yield strength is 178 MPa, tensile strength is 280 MPa, and elongation is 11.23%.

[0046] Example 5 A preparation method of a heat - treatment - free self - strengthening Al - Mg aluminum alloy, the specific steps are as follows: Step 1: Prepare pure aluminum, pure magnesium ingot, pure zinc ingot, pure copper ingot and master alloys Al - Si, Al - Fe and Al - 5Mo as raw materials; among them, Mg accounts for 4.78% of the total mass of all raw materials, Si accounts for 1.25% of the total mass of all raw materials, Zn accounts for 0.41% of the total mass of all raw materials, Cu accounts for 0.87% of the total mass of all raw materials, Mo accounts for 0.42% of the total mass of all raw materials, Fe accounts for 0.41% of the total mass of all raw materials, and the balance is Al; The purity of pure aluminum ≥ 99.98%, the purity of pure magnesium ≥ 99.98%, the purity of pure zinc ≥ 99.98%, and the purity of pure copper ≥ 99.98%; Step 2: Under the condition of argon atmosphere, put the crucible into the resistance furnace for preheating, and set the preheating temperature to 410°C - 460°C; Step 3: Under the condition of argon atmosphere, place pure aluminum in the crucible, adjust the temperature to 760°C, and keep it warm for 20 minutes to form aluminum melt; after all the pure aluminum is melted, stir and skim the slag in time; control the stirring speed at 200 revolutions per minute, and the stirring time is 3 minutes; Step 4: Under the condition of argon atmosphere, add the preheated pure copper ingot, Al - Si, Al - Fe and Al - 5Mo master alloys, and keep it warm at 745°C for 15 minutes; Under the condition of argon atmosphere, adjust the furnace temperature to 740°C, add the preheated industrial pure magnesium and pure zinc ingot, stir until completely melted and keep it warm for 25 minutes. Control the stirring speed at 200 revolutions per minute, and the stirring time is 3 minutes; Step 5: Under the condition of argon atmosphere, adjust the furnace temperature to 710°C, add the grain refiner Al5TiB metal rod, and the addition amount of the grain refiner is 0.4% of the total mass of the melt, stir for 5 minutes, let it stand for 15 minutes and then skim the slag; Step 6: Under the condition of argon atmosphere, adjust the furnace temperature to 720°C, stir until completely melted and keep it warm for 10 minutes, degas with hexachloroethane for 5 minutes, and the addition amount of hexachloroethane powder is 1.0% of the mass of the melt. Then take out the crucible, skim the slag at 700°C, and pour the molten liquid into the water - cooled copper mold to cast the aluminum liquid into a flat ingot; Step 7: Carry out modification treatment on the as - cast blank, and the specific process conditions are: in an environment with a temperature of 470°C, and keep it warm for 10 hours, and cool it by water quenching; Step 8: Carry out heat treatment on the modified blank, and the specific process conditions are: in an environment with a temperature of 155°C, and keep it warm for 21 hours, and the cooling method is air cooling. Its yield strength is 232 MPa, tensile strength is 360 MPa, and elongation is 8.56%.

[0047] Example 6 A preparation method of a heat - treatment - free self - strengthening Al - Mg aluminum alloy, the specific steps are as follows: Step 1: Prepare pure aluminum, pure magnesium ingot, pure zinc ingot, pure copper ingot and master alloys Al - Si, Al - Fe and Al - 5Mo as raw materials; among them, Mg accounts for 5.68% of the total mass of all raw materials, Si accounts for 1.87% of the total mass of all raw materials, Zn accounts for 0.86% of the total mass of all raw materials, Cu accounts for 0.75% of the total mass of all raw materials, Mo accounts for 0.5% of the total mass of all raw materials, Fe accounts for 0.01% of the total mass of all raw materials, and the balance is Al; The purity of pure aluminum is ≥99.98%, the purity of pure magnesium is ≥99.98%, the purity of pure zinc is ≥99.98%, and the purity of pure copper is ≥99.98%; Step 2: Under the condition of argon atmosphere, put the crucible into the resistance furnace for preheating, and the preheating temperature is set at 410°C - 460°C; Step 3: Under the condition of argon atmosphere, place pure aluminum in the crucible, adjust the temperature to 720°C, and keep it warm for 30 minutes to form aluminum melt; after all the pure aluminum is melted, stir and skim the slag in time; the stirring speed is controlled at 200 revolutions per minute, and the stirring time is 3 minutes; Step 4: Under the condition of argon atmosphere, add the preheated pure copper ingot, Al-Si, Al-Fe and Al-5Mo master alloys, and keep it warm at 748°C for 17 minutes; Under the condition of argon atmosphere, adjust the furnace temperature to 750°C, add the preheated industrial pure magnesium and pure zinc ingot, stir until completely melted and keep it warm for 20 minutes. The stirring speed is controlled at 200 revolutions per minute, and the stirring time is 3 minutes; Step 5: Under the condition of argon atmosphere, adjust the furnace temperature to 730°C, add the grain refiner Al5TiB metal rod, and the addition amount of the grain refiner is 0.45% of the total mass of the melt, stir for 5 minutes, skim the slag after standing for 15 minutes; Step 6: Under the condition of argon atmosphere, adjust the furnace temperature to 725°C, stir until completely melted and keep it warm for 10 minutes, degas with hexachloroethane for 5 minutes, and the addition amount of hexachloroethane powder is 0.65% of the mass of the melt. Then take out the crucible, skim the slag at 700°C, and pour the molten liquid into the water-cooled copper mold to cast the aluminum liquid into a flat ingot; Step 7: Carry out modification treatment on the as-cast blank, and the specific process conditions are: in an environment with a temperature of 465°C, and keep it warm for 8 hours, and cool by water quenching; Step 8: Carry out heat treatment on the modified blank, and the specific process conditions are: in an environment with a temperature of 170°C, and keep it warm for 17 hours, and the cooling method is air cooling. Its yield strength is 248 MPa, tensile strength is 361 MPa, and elongation is 9.02%.

[0048] Example 7 A preparation method of a heat-treatable self-strengthening Al-Mg aluminum alloy, the specific steps are as follows: Step 1: Prepare pure aluminum, pure magnesium ingot, pure zinc ingot, pure copper ingot and master alloys Al-Si, Al-Fe and Al-5Mo as raw materials; among them, Mg accounts for 4.35% of the total mass of all raw materials, Si accounts for 2.10% of the total mass of all raw materials, Zn accounts for 1.46% of the total mass of all raw materials, Cu accounts for 0.89% of the total mass of all raw materials, Mo accounts for 0.25% of the total mass of all raw materials, Fe accounts for 0.25% of the total mass of all raw materials, and the balance is Al; The purity of pure aluminum ≥ 99.98%, the purity of pure magnesium ≥ 99.98%, the purity of pure zinc ≥ 99.98%, and the purity of pure copper ≥ 99.98%; Step 2: Under the condition of argon atmosphere, put the crucible into the resistance furnace for preheating, and the preheating temperature is set at 410°C - 460°C; Step 3: Under the condition of argon atmosphere, place pure aluminum in the crucible, adjust the temperature to 745°C, and keep it warm for 30 min to form aluminum melt; after all the pure aluminum is melted, stir and skim the slag in time; the stirring speed is controlled at 200 revolutions per minute, and the stirring time is 3 min; Step 4: Under the condition of argon atmosphere, add the preheated pure copper ingot, Al - Si, Al - Fe and Al - 5Mo master alloys, and keep it warm at 745°C for 16 - 22 min; Under the condition of argon atmosphere, adjust the furnace temperature to 750°C, add the pre - heated industrial pure magnesium and pure zinc ingot, stir until completely melted and keep it warm for 20 min. The stirring speed is controlled at 200 revolutions per minute, and the stirring time is 3 min; Step 5: Under the condition of argon atmosphere, adjust the furnace temperature to 700°C, add the refining agent Al5TiB metal rod, and the addition amount of the refining agent is 0.45% of the total mass of the melt, stir for 5 min, stand for 15 min and then skim the slag; Step 6: Under the condition of argon atmosphere, adjust the furnace temperature to 720°C, stir until completely melted and keep it warm for 10 min, use hexachloroethane for degassing for 5 min, and the addition amount of hexachloroethane powder is 0.80% of the mass of the melt. Then take out the crucible, skim the slag at 700°C, and pour the molten liquid into the water - cooled copper mold to cast the aluminum liquid into a flat ingot; Step 7: Carry out modification treatment on the as - cast blank, and the specific process conditions are: in an environment with a temperature of 455°C, and keep it warm for 7 h, and cool by water quenching; Step 8: Carry out heat treatment on the blank after modification treatment, and the specific process conditions are: in an environment with a temperature of 160°C, and keep it warm for 17 h, and the cooling method is air cooling. Its yield strength is 228 MPa, tensile strength is 304 MPa, and elongation is 10.25%.

[0049] Example 8 A preparation method of a heat - treatment - free self - strengthening Al - Mg aluminum alloy, the specific steps are as follows: Step 1: Prepare pure aluminum ingots, pure magnesium ingots, pure zinc ingots, pure copper ingots, and master alloys Al-Si, Al-Fe, and Al-5Mo as raw materials; where Mg accounts for 4.56% of the total mass of all raw materials, Si accounts for 1.89% of the total mass of all raw materials, Zn accounts for 0.47% of the total mass of all raw materials, Cu accounts for 1.46% of the total mass of all raw materials, Mo accounts for 0.30% of the total mass of all raw materials, Fe accounts for 0.24% of the total mass of all raw materials, and the balance is Al; The purity of pure aluminum ≥ 99.98%, the purity of pure magnesium ≥ 99.98%, the purity of pure zinc ≥ 99.98%, and the purity of pure copper ≥ 99.98%; Step 2: Under the condition of an argon atmosphere, place the crucible in a resistance furnace for preheating, and set the preheating temperature to 410 °C - 460 °C; Step 3: Under the condition of an argon atmosphere, place pure aluminum in the crucible, adjust the temperature to 745 °C, and hold for 25 min to form an aluminum melt; after all the pure aluminum has melted, stir and skim the slag in a timely manner; control the stirring speed at 200 revolutions per minute, and the stirring time is 3 min; Step 4: Under the condition of an argon atmosphere, add the preheated pure copper ingot, Al-Si, Al-Fe, and Al-5Mo master alloys, and hold at 740 °C for 13 min; Under the condition of an argon atmosphere, adjust the furnace temperature to 750 °C, add the preheated commercial pure magnesium and pure zinc ingots, stir until completely melted and hold for 17 min. Control the stirring speed at 200 revolutions per minute, and the stirring time is 3 min; Step 5: Under the condition of an argon atmosphere, adjust the furnace temperature to 710 °C, add the grain refiner Al5TiB metal rod, and the addition amount of the grain refiner is 0.45% of the total mass of the melt, stir for 5 min, let stand for 15 min, and then skim the slag; Step 6: Under the condition of an argon atmosphere, adjust the furnace temperature to 720 °C, stir until completely melted and hold for 10 min, degas with hexachloroethane for 5 min, and the addition amount of hexachloroethane powder is 0.65% of the mass of the melt. Then take out the crucible, skim the slag at 700 °C, and pour the molten liquid into a water-cooled copper mold to cast the aluminum liquid into a flat ingot; Step 7: Perform modification treatment on the as-cast billet. The specific process conditions are: in an environment with a temperature of 460 °C, and hold for 6 h, and cool by water quenching; Step 8: Perform heat treatment on the billet after modification treatment. The specific process conditions are: in an environment with a temperature of 155 °C, and hold for 17 h, and the cooling method is air cooling. Its yield strength is 248 MPa, the tensile strength is 342 MPa, and the elongation is 9.25%.

[0050] Example 9 A preparation method of a heat-treatable self-strengthening Al-Mg aluminum alloy, the specific steps are as follows: Step 1: Prepare pure aluminum ingots, pure magnesium ingots, pure zinc ingots, pure copper ingots, and master alloys Al-Si, Al-Fe, and Al-5Mo as raw materials; where Mg accounts for 5.63% of the total mass of all raw materials, Si accounts for 0.23% of the total mass of all raw materials, Zn accounts for 0.87% of the total mass of all raw materials, Cu accounts for 2.00% of the total mass of all raw materials, Mo accounts for 0.18% of the total mass of all raw materials, Fe accounts for 0.23% of the total mass of all raw materials, and the balance is Al; The purity of pure aluminum ≥ 99.98%, the purity of pure magnesium ≥ 99.98%, the purity of pure zinc ≥ 99.98%, and the purity of pure copper ≥ 99.98%; Step 2: Under the condition of an argon atmosphere, place the crucible in a resistance furnace for preheating, and set the preheating temperature to 410°C - 460°C; Step 3: Under the condition of an argon atmosphere, place pure aluminum in the crucible and adjust the temperature to 735°C, hold for 25 minutes to form an aluminum melt; after all the pure aluminum has melted, stir and skim the slag in a timely manner; control the stirring speed at 200 revolutions per minute, and the stirring time is 3 minutes; Step 4: Under the condition of an argon atmosphere, add the preheated pure copper ingot, Al-Si, Al-Fe, and Al-5Mo master alloys, and hold at 745°C for 15 minutes; Under the condition of an argon atmosphere, adjust the furnace temperature to 740°C, add the preheated commercial pure magnesium and pure zinc ingots, stir until completely melted and then hold for 17 minutes. Control the stirring speed at 200 revolutions per minute, and the stirring time is 3 minutes; Step 5: Under the condition of an argon atmosphere, adjust the furnace temperature to 720°C, add the grain refiner Al5TiB metal rod, and the addition amount of the grain refiner is 0.45% of the total mass of the melt, stir for 5 minutes, stand for 15 minutes and then skim the slag; Step 6: Under the condition of an argon atmosphere, adjust the furnace temperature to 720°C, stir until completely melted and hold for 10 minutes, degas with hexachloroethane for 5 minutes, and the addition amount of hexachloroethane powder is 0.70% of the mass of the melt. Then take out the crucible, skim the slag at 700°C, and pour the molten liquid into a water-cooled copper mold to cast the aluminum liquid into a flat ingot; Step 7: Carry out modification treatment on the as-cast billet, and the specific process conditions are: in an environment with a temperature higher than 460°C, and keep holding for 6 hours, and cool by water quenching; Step 8: Carry out heat treatment on the modified billet, and the specific process conditions are: in an environment with a temperature of 160°C, and keep holding for 17 hours, and the cooling method is air cooling. Its yield strength is 263 MPa, tensile strength is 384 MPa, and elongation is 7.35%.

Claims

1. An as-cast heat-treatable Al-Mg alloy, characterized in that, Its chemical composition by mass percentage: Mg: 4.35% - 5.63%, Si: 0.23% - 2.10%, Zn: 0.41% - 1.46%, Cu: 0.35% - 2.00%, Mo: 0.05% - 0.50%, Fe: 0.01% - 0.41%, and the balance is Al.

2. The heat-treatment-free self-strengthening Al-Mg aluminum alloy according to claim 1, wherein, The chemical composition satisfies the following relationships: 0% ≤ Si + Zn + Cu + Mo + Fe ≤ 7.0%; 5.0% ≤ Mg + 0.5(Si + Zn + Cu) + 0.3Mo + 0.2Fe ≤ 8.0%.

3. A method for preparing a heat-treatment-free self-strengthening Al-Mg aluminum alloy according to claim 1 or 2, characterized in that, It includes the following steps: Step 1: Using pure aluminum and pure magnesium ingots, pure zinc ingots, pure copper ingots, and intermediate alloys Al - Si, Al - Fe, and Al - 5Mo as raw materials; where Mg accounts for 4.35% - 5.63% of the total mass of all raw materials, Si accounts for 0.23% - 2.10% of the total mass of all raw materials, Zn accounts for 0.41% - 1.46% of the total mass of all raw materials, Cu accounts for 0.35% - 2.00% of the total mass of all raw materials, Mo accounts for 0.05% - 0.50% of the total mass of all raw materials, Fe accounts for 0.01% - 0.41% of the total mass of all raw materials, and the balance is Al; Step 2: Under the condition of protective atmosphere, put the crucible into the resistance furnace and heat it. When the temperature is adjusted to 410°C - 460°C, add the pre - heated pure aluminum. Step 3: Under the condition of protective atmosphere, adjust the temperature of the resistance furnace to 700°C - 760°C. After all the pure aluminum is melted, stir and skim the slag. Step 4: Under the condition of protective atmosphere, add pure copper ingots, intermediate alloys Al - Si, Al - Fe, and Al - 5Mo in sequence. After they are melted, keep them warm for 10 min - 15 min. When the temperature reaches 740°C - 760°C, add pure magnesium ingots and pure zinc ingots until they are molten. Stir until completely melted and then keep warm for 10 min - 25 min. Step 5: Under the condition of protective atmosphere, add a grain refiner to the alloy liquid, stir, and skim the slag after standing. Step 6: Under the condition of protective atmosphere, use hexachloroethane for degassing, and stir and skim the slag. Step 7: Under the condition of protective atmosphere, skim the slag at a temperature of 700°C - 735°C, and then pour the melt into a water - cooled mold to obtain a as - cast blank. Step 8: First, perform modification treatment on the cast aluminum alloy ingot, and finally perform heat treatment to obtain a heat - treatable self - strengthening Al - Mg aluminum alloy.

4. The preparation method of a heat-treatment-free self-strengthening Al-Mg aluminum alloy according to claim 3, characterized in that, In the said Step 5, under the condition of protective atmosphere, adjust the temperature of the resistance furnace to 700°C - 750°C, add a grain refiner to the alloy liquid, stir for 5 min - 10 min, and skim the slag after standing for 15 min - 20 min.

5. The preparation method of a heat-treatment-free self-strengthening Al-Mg aluminum alloy according to claim 3, wherein, In the said Step 5, the grain refiner used is an Al5TiB metal rod, and the addition amount of the grain refiner is 0.4% - 0.45% of the melt mass.

6. The preparation method of a heat-treatment-free self-strengthening Al-Mg aluminum alloy according to claim 3, characterized in that, In the said Step 6, under the condition of protective atmosphere, adjust the temperature of the resistance furnace to 720°C - 745°C, stir and keep warm for 10 min - 15 min, use hexachloroethane for degassing, the addition amount of hexachloroethane powder is 0.65% - 1.0% of the melt mass, and the degassing time is 5 min - 8 min.

7. The preparation method of a heat-treatment-free self-strengthening Al-Mg aluminum alloy according to claim 3, characterized in that, In the step 7, the melt in the crucible is poured into a water-cooled mold, and the solidification rate of the material in the water-cooled mold is controlled by the cooling water flow rate to be 180 mm / min to 480 mm / min; during casting, the water pressure of the cooling water introduced into the water-cooled mold is 0.10 MPa to 0.40 MPa; the water flow rate introduced into the water-cooled mold is 1.5 m / s to 3 m / s, and the water temperature is controlled in the range of 15 °C to 35 °C.

8. The preparation method of a heat-treatment-free self-strengthening Al-Mg aluminum alloy according to claim 3, characterized in that, In the step 8, the modification treatment process is as follows: the temperature is 450 °C to 500 °C, the heat preservation time is 5 h to 10 h, and the cooling method is water quenching.

9. The preparation method of a heat-treatment-free self-strengthening Al-Mg aluminum alloy according to claim 3, wherein, In the step 8, the heat treatment process is as follows: the temperature is 140 °C to 180 °C, the heat preservation time is 15 h to 25 h, and the cooling method is air cooling.

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