Heat-treatment-free high-strength and high-toughness aluminum alloy as well as preparation method and application thereof

Abstract

The invention provides a heat-treatment-free high-strength and high-toughness aluminum alloy and a preparation method and application thereof.The high-strength and high-toughness aluminum alloy comprises Al, Si, Fe, Cu, Mn, Mg, Zn, Ca, Pb, Sb, Be, Ti, Mo, V, Zr, Sr and inevitable impurities, and the preparation method comprises the steps that (1) aluminum raw materials are molten to obtain molten aluminum; (2) doping components are added into the molten aluminum, component regulation and control and cooling treatment are carried out, and then a refiner is added for alloying; (3) a refining agent is added into the molten aluminum for refining and degassing, standing is carried out after slagging-off, and component confirmation is carried out; and (4) adding an alterant into the molten aluminum, blowing and stirring, discharging soup, and carrying out die casting to obtain the high-strength and high-toughness aluminum alloy. The heat-treatment-free high-strength and high-toughness aluminum alloy is produced through a matching mechanism among various elements and by means of specific smelting conditions, the performance requirements of automobile structural parts are fully met, and the application prospect of the material is expanded.

Description

Technical Field

[0001] The present invention belongs to the technical field of alloy manufacturing, and relates to a high-strength and high-toughness aluminum alloy, and in particular to a high-strength and high-toughness aluminum alloy that does not require heat treatment, and a preparation method and application thereof. Background Art

[0002] At present, in the context of reducing carbon emissions, the global automotive industry is committed to lightweighting automobiles. Among them, the idea of ​​replacing conventional automotive steel with aluminum alloys has been widely recognized and applied. At present, Germany's Rheinmetall's Silafont-36 series aluminum alloys and Alcan's Aural-2 and Aural-3 aluminum alloys have been widely used in the automotive industry. However, the above aluminum alloys all need to undergo heat treatment to meet the needs of the automotive industry, which not only increases the production process and increases the production cost, but also the product bubbles and deformation caused by heat treatment reduce the product qualification rate.

[0003] In addition, the heat treatment-free materials used in China are still in the early stages. Cast products are prone to cold shut and under-casting, internal shrinkage holes can hardly meet the needs of the automotive industry, and the mechanical properties are relatively low. These problems have limited the further promotion and application of the materials.

[0004] It can be seen that how to provide a high-strength and high-toughness aluminum alloy that does not require heat treatment and a preparation method thereof to fully meet the performance requirements of automotive structural parts and expand the application prospects of the material has become an urgent problem that technical personnel in this field need to solve. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a high-strength and high-toughness aluminum alloy that does not require heat treatment, and a preparation method and application thereof. Through the matching mechanism between various elements and with the help of specific smelting conditions, a high-strength and high-toughness aluminum alloy that does not require heat treatment is produced, which fully meets the performance requirements of automotive structural parts and expands the application prospects of the material.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a high-strength and high-toughness aluminum alloy that does not require heat treatment. The constituent elements of the high-strength and high-toughness aluminum alloy include, by mass percentage:

[0008] Si 7%-8%;

[0009] Fe ≤0.14%;

[0010] Cu ≤0.008%;

[0011] Mn 0.6%-0.7%;

[0012] Mg 0.2%-0.26%;

[0013] Zn ≤0.005%;

[0014] Ca ≤0.001%;

[0015] Pb ≤0.003%;

[0016] Sb ≤0.0003%;

[0017] Be ≤0.00008%;

[0018] Ti 0.08%-0.15%;

[0019] Mo 0.01%-0.08%;

[0020] V 0.01%-0.08%;

[0021] Zr 0.06%-0.25%;

[0022] Sr 0.016%-0.026%;

[0023] The balance is Al and inevitable impurities.

[0024] In the present invention, the mass percentage of Si is 7%-8%, for example, it can be 7.0%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, 7.8%, 7.9% or 8.0%, the mass percentage of Fe is ≤0.14%, for example, it can be 0.02%, 0.04%, 0.06%, 0.08%, 0.10%, 0.12% or 0.14%, the mass percentage of Cu is ≤0.008%, for example, it can be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007% or 0.008%, the mass percentage of Mn is 0.6%-0.7%, for example, The mass percentage of Mg is 0.20%-0.26%, for example, it can be 0.20%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25% or 0.26%, the mass percentage of Zn is ≤0.005%, for example, it can be 0.001%, 0.002%, 0.003%, 0.004% or 0.005%, and the mass percentage of Ca is ≤0.001%, for example, it can be 0.0002%, 0.0004%, 0.0006%, 0.0008% or 0.0010%, the mass percentage of Pb is ≤0.003%, for example, it can be 0.0005%, 0.0010%, 0.0015%, 0.0020%, 0.0025% or 0.0030%, the mass percentage of Sb is ≤0.0003%, for example, it can be 0.0001%, 0.0002% or 0.0003%, the mass percentage of Be is ≤0.00008%, for example, it can be 0.00002%, 0.00004%, 0.0006% or 0.00008%, and the mass percentage of Ti is 0.08%-0.15%, for example, it can be 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.1 3%, 0.14% or 0.15%, the mass percentage of Mo is 0.01%-0.08%, for example, it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07% or 0.08%, the mass percentage of V is 0.01%-0.08%, for example, it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07% or 0.08%, the mass percentage of Zr is 0.06%-0.25%, for example, it can be 0.06%, 0.08%, 0.10%, 0.12%, 0.14%, 0.16%, 0.18%, 0.20%, 0.22%, 0.24% or 0.25%, the mass percentage of Sr is 0.016%-0.026%, for example, it can be 0.016%, 0.018%, 0.020%, 0.022%, 0.024% or 0.026%, but it is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable. .

[0025] The aluminum alloy provided by the present invention uses relatively low-cost elements without adding high-cost trace elements such as rare earth. Through the synergistic combination of various elements, a high-strength and high-toughness aluminum alloy is finally obtained, which fully meets the performance requirements of automobile structural parts and expands the application prospects of the material.

[0026] Specifically, Si is one of the commonly used alloying elements in aluminum alloys. It can form a eutectic with Al, thereby improving the strength and hardness of the alloy, while improving casting performance, reducing shrinkage, and preventing hot cracking tendency. Si can also improve the high-temperature moldability of the alloy, improve tensile strength, hardness and machinability, but too much Si will reduce elongation, so the mass percentage of Si is limited to 7%-8%.

[0027] Specifically, Fe usually exists as an impurity element in aluminum alloys. Since an increase in the Fe content will form a coarse impurity phase, which in turn affects the fracture toughness and short transverse mechanical properties of the alloy, the mass percentage of Fe is limited to ≤0.14%.

[0028] Specifically, Cu has obvious solid solution strengthening and aging strengthening effects in aluminum alloys. The addition of Cu can increase the tensile strength and yield limit of the alloy and improve the cutting processability of the alloy, but excessive addition of Cu will also reduce the corrosion resistance and plasticity of the alloy and increase the tendency of hot cracking, so the mass percentage of Cu is limited to ≤0.008%.

[0029] Specifically, Mn can improve the strength and hardness of aluminum alloys, while improving corrosion resistance; Mn can also prevent the recrystallization process of aluminum alloys, increase the recrystallization temperature, and significantly refine the recrystallized grains. In addition, Mn can form compounds with impurity Fe to reduce the harmful effects of Fe, so the mass percentage of Mn is limited to 0.6%-0.7%.

[0030] Specifically, Mg is an important strengthening element in aluminum alloys, which can significantly improve the tensile strength of the alloy. 2 Si eutectic structure can significantly improve the strength of the alloy; Mg can also improve the corrosion resistance and welding performance of the alloy. However, too high Mg content will cause hot cracks in the alloy, so the mass percentage of Mg is limited to 0.20%-0.26%.

[0031] Specifically, Zn can improve the strength and hardness of aluminum alloys, especially when added together with Mg, it can form a strengthening phase Mg / Zn2 , which has a significant strengthening effect on the alloy, but excessive addition of Zn will also lead to a tendency of stress corrosion cracking, so the mass percentage of Zn is limited to ≤0.005%.

[0032] Specifically, Ti is mainly used as a refiner in aluminum alloys, which can refine grains and increase recrystallization temperature. Ti can also improve the superplasticity and cutting performance of the alloy, so the mass percentage of Ti is limited to 0.08%-0.15%.

[0033] Specifically, Mo can form fine dispersed phases in aluminum alloys, which help improve the strength of the alloy during the die-casting process; the addition of Mo can also improve the wear resistance of aluminum alloys because it can promote the formation of a harder surface phase. In addition, Mo is also used to improve the corrosion resistance of the alloy, so the mass percentage of Mo is limited to 0.01%-0.08%.

[0034] Specifically, the role of V in aluminum alloy is similar to that of Mo, which can form a hard dispersed phase, thereby improving the strength and hardness of the alloy; the addition of V can also improve the thermal stability of the aluminum alloy, helping to maintain the performance of the alloy at high temperatures. In addition, V can also refine the grains of the aluminum alloy and further improve the mechanical properties of the material, so the mass percentage of V is limited to 0.01%-0.08%.

[0035] Specifically, Zr, as a micro-alloying element, can improve the heat resistance and stress corrosion resistance of aluminum alloys, so the mass percentage of Zr is limited to 0.06%-0.25%.

[0036] Specifically, Sr can improve the casting properties of aluminum alloys and reduce casting defects such as shrinkage and cracks. Sr added to aluminum alloys, especially in AZ series alloys, can significantly improve the alloy's microstructure, room temperature and high temperature properties, refine the grains, and improve the yield strength and creep resistance. The addition of Sr can also improve the corrosion resistance of the alloy by modifying and refining the second phase such as β-Mg 17 Al 12 , reducing its volume fraction and making it tend to be fine and dispersed, thereby improving the corrosion resistance of the alloy, so the mass percentage of Sr is limited to 0.016%-0.026%.

[0037] Preferably, measured in percentage by mass, the elements in the high-strength and high-toughness aluminum alloy satisfy: (Fe+Mn) / Zr≤10, for example, it can be 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, Mo+V≥0.04%, for example, it can be 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09% or 0.10%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] The present invention further ensures the high strength, toughness and castability of the material performance by limiting the content relationship between Fe, Mn, Zr, Mo and V. Appropriate amounts of Mo and V form fine dispersed phases during die casting to improve the strength of the alloy at room temperature, and the introduction of Zr can significantly improve the toughness of the die-casting alloy.

[0039] Specifically, the present invention ensures that the content of Fe and Mn in the alloy is not too high by limiting (Fe+Mn) / Zr≤10, and at the same time ensures that the content of Zr is sufficient to refine the grains and suppress the adverse effects of Fe and Mn; further, the present application ensures that there are enough Mo and V in the alloy to form a dispersed phase by limiting Mo+V≥0.04%, thereby improving the strength and hardness of the alloy. The above-mentioned composition design helps to balance the strength, toughness, corrosion resistance and processing performance of the alloy, so that the alloy meets the performance requirements of automotive structural parts without heat treatment.

[0040] Preferably, measured in percentage by mass, the impurities in the high-strength and high-toughness aluminum alloy satisfy: a single impurity content ≤ 0.05%, for example, it may be 0.01%, 0.02%, 0.03%, 0.04% or 0.05%, and the total impurity content ≤ 0.15%, for example, it may be 0.02%, 0.04%, 0.06%, 0.08%, 0.10%, 0.12%, 0.14% or 0.15%, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0041] In the present invention, since the impurity elements will form coarse impurity phases in the aluminum alloy, and these impurity phases will seriously affect the fracture toughness and short transverse mechanical properties of the aluminum alloy, and the presence of the impurity elements may destroy the passivation film of the aluminum alloy, thereby causing a decrease in corrosion resistance, and even form low-melting point compounds in the aluminum alloy, these compounds are likely to cause thermal cracks during the solidification process. Therefore, the present invention strictly limits the content of a single impurity and the total amount of impurities, thereby significantly improving the mechanical properties and corrosion resistance of the aluminum alloy, while reducing the thermal cracking tendency of the material.

[0042] Preferably, the yield strength of the high-strength and high-toughness aluminum alloy is ≥130MPa, for example, it can be 130MPa, 135MPa, 140MPa, 145MPa, 150MPa, 155MPa or 160MPa, the tensile strength is ≥270MPa, for example, it can be 270MPa, 275MPa, 280MPa, 285MPa, 290MPa, 295MPa or 300MPa, and the elongation is ≥10%, for example, it can be 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28% or 30%, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] In a second aspect, the present invention provides a method for preparing the high-strength and high-toughness aluminum alloy as described in the first aspect, the preparation method comprising the following steps:

[0044] (1) Melting aluminum raw materials and removing slag during the melting process to obtain aluminum liquid;

[0045] (2) adding doping components to the aluminum liquid and performing composition control and cooling treatment, wherein the cooling treatment includes air blowing cooling, and then adding a refiner for alloying;

[0046] (3) Add refining agent to the aluminum liquid for refining and degassing, let it stand after slagging and confirm the composition;

[0047] (4) Add a modifier to the aluminum liquid, blow air and stir it to get the liquid, and then die-cast it to obtain a high-strength and high-toughness aluminum alloy.

[0048] The air blowing for cooling in step (2), the refining and degassing in step (3) and the air blowing and stirring in step (4) are each independently carried out with nitrogen, and the nitrogen is obtained by converting liquid nitrogen into gas at the smelting site and directly applying it to the corresponding process. The purity of the obtained nitrogen is ≥5N grade, for example, it can be 5N grade, 5N5 grade, 6N grade, 6N5 grade, 7N grade, 7N5 grade or 8N grade, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0049] The present invention specifically limits the gas used for air blowing for cooling, refining degassing and air blowing stirring during the smelting process to high-purity nitrogen converted from liquid nitrogen at the smelting site, which has a better degassing effect and avoids the adverse effects of impurity elements in the nitrogen on material properties.

[0050] Preferably, the melting in step (1) is carried out in a reverberatory furnace, and the melting temperature is 760-780°C, for example, 760°C, 762°C, 764°C, 766°C, 768°C, 770°C, 772°C, 774°C, 776°C, 778°C or 780°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0051] Preferably, the aluminum raw material in step (1) includes primary aluminum and recycled aluminum, and the mass ratio of primary aluminum to recycled aluminum is 1:(0.5-2), for example, it can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0052] The aluminum raw material used in the present invention includes recycled aluminum, that is, not all of it is primary aluminum, thus achieving the purpose of energy conservation and emission reduction and meeting the requirements of green production.

[0053] Preferably, the doping components in step (2) include metallic silicon, electrolytic manganese, pure magnesium ingot, aluminum-titanium alloy, aluminum-vanadium alloy, aluminum-molybdenum alloy and aluminum-zirconium alloy.

[0054] Preferably, the target temperature of the cooling treatment in step (2) is 700-740°C, for example, it can be 700°C, 705°C, 710°C, 715°C, 720°C, 725°C, 730°C, 735°C or 740°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0055] Preferably, the refiner in step (2) comprises Al-Ti-B alloy.

[0056] Preferably, the refining and degassing temperature in step (3) is 700-740°C, for example, 700°C, 705°C, 710°C, 715°C, 720°C, 725°C, 730°C, 735°C or 740°C, and the time is 15-30 min, for example, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0057] Preferably, the absolute pressure of nitrogen used for refining and degassing in step (3) is 0.25-0.35 MPa, for example, it can be 0.25 MPa, 0.26 MPa, 0.27 MPa, 0.28 MPa, 0.29 MPa, 0.3 MPa, 0.31 MPa, 0.32 MPa, 0.33 MPa, 0.34 MPa or 0.35 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0058] Preferably, the standing time in step (3) is ≥ 10 min, for example, it can be 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, 22 min, 24 min, 26 min, 28 min or 30 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0059] Preferably, after the composition confirmation in step (3), a density equivalent test and a slag content test are also included to ensure that the density equivalent is ≤0.5%, for example, it can be 0.1%, 0.2%, 0.3%, 0.4% or 0.5%, and the slag content K is ≤2 / 20, for example, it can be 1 / 20 or 2 / 20.

[0060] In the present invention, the slag content is specifically: the ratio of the total number of particles (large + medium + small) to the number of counted pieces.

[0061] Preferably, the modifier in step (4) comprises an aluminum strontium alloy.

[0062] Preferably, the time of the blowing and stirring in step (4) is ≤ 5 min, for example, it can be 1 min, 2 min, 3 min, 4 min or 5 min, but it is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0063] Preferably, during the die casting in step (4), the temperature of the aluminum liquid is controlled to be 660-680°C, for example, 660°C, 662°C, 664°C, 666°C, 668°C, 670°C, 672°C, 674°C, 676°C, 678°C or 680°C, the temperature of the mold is 150-250°C, for example, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C or 250°C, and the casting pressure is 70-80MPa. a, for example, it can be 70MPa, 71MPa, 72MPa, 73MPa, 74MPa, 75MPa, 76MPa, 77MPa, 78MPa, 79MPa or 80MPa, the injection time is 8-12s, for example, it can be 8s, 9s, 10s, 11s or 12s, and the cooling time is 20-25s, for example, it can be 20s, 21s, 22s, 23s, 24s or 25s, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0064] As a preferred technical solution of the second aspect of the present invention, the preparation method comprises the following steps:

[0065] (1) Adding primary aluminum and recycled aluminum in a mass ratio of 1:(0.5-2) into a reverberatory furnace, controlling the melting temperature to 760-780°C, and removing slag during the melting process to obtain aluminum liquid;

[0066] (2) adding doping components to the aluminum liquid and performing composition control and cooling treatment, wherein the doping components include metallic silicon, electrolytic manganese, pure magnesium ingot, aluminum-titanium alloy, aluminum-vanadium alloy, aluminum-molybdenum alloy and aluminum-zirconium alloy, and the cooling treatment includes air blowing cooling, with a target temperature of 700-740°C, and then adding Al-Ti-B alloy as a refiner for alloying;

[0067] (3) Add refining agent to the aluminum liquid, and perform refining and degassing at 700-740℃ for 15-30min, using nitrogen at an absolute pressure of 0.25-0.35MPa. After slagging, let it stand for more than 10min and confirm the composition, then perform density equivalent test and slag content test to ensure that the density equivalent is ≤0.5% and the slag content K is ≤2 / 20;

[0068] (4) Aluminum strontium alloy is added to the aluminum liquid as a modifier, and the liquid is blown and stirred to produce a soup, which is then die-casted. The temperature of the aluminum liquid is controlled at 660-680°C, the temperature of the mold is 150-250°C, the casting pressure is 70-80MPa, the injection time is 8-12s, and the cooling time is 20-25s to obtain a high-strength and high-toughness aluminum alloy.

[0069] The air blowing and cooling in step (2), the refining and degassing in step (3) and the air blowing and stirring in step (4) are each independently carried out using nitrogen, and the nitrogen is liquid nitrogen converted into gas at the smelting site and directly used in the corresponding process, and the purity of the obtained nitrogen is ≥5N grade.

[0070] In a third aspect, the present invention provides an application of the high-strength and high-toughness aluminum alloy as described in the first aspect, wherein the high-strength and high-toughness aluminum alloy is used to manufacture automotive structural parts.

[0071] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0072] Compared with the prior art, the present invention has the following beneficial effects:

[0073] (1) The aluminum alloy provided by the present invention uses relatively low-cost elements and does not add high-cost trace elements such as rare earth. Through the matching mechanism between various elements and with the help of specific smelting conditions, a high-strength and high-toughness aluminum alloy that does not require heat treatment is finally produced, which fully meets the performance requirements of automotive structural parts and expands the application prospects of the material.

[0074] (2) The present invention specifically limits the gas used for air blowing for cooling, refining degassing and air blowing for stirring during the smelting process to high-purity nitrogen converted from liquid nitrogen at the smelting site, which has a better degassing effect and avoids the adverse effects of impurity elements in nitrogen on material properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 This is a metallographic micrograph of the aluminum alloy cross section provided in Example 1. DETAILED DESCRIPTION

[0076] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0077] Examples 1-5 and Comparative Examples 1-2

[0078] The present group of embodiments and comparative examples respectively provide an aluminum alloy. The relationship between the constituent elements and the element contents of the aluminum alloy, measured in mass percentage, is shown in Table 1 below.

[0079] Table 1

[0080]

[0081] The balance is Al and unavoidable impurities, and the content of a single impurity is ≤0.05%, and the total amount of impurities is ≤0.15%.

[0082] Preparation Example 1

[0083] This preparation example is used to prepare the aluminum alloy described in Example 1, and the specific preparation method includes the following steps:

[0084] (1) Adding primary aluminum and recycled aluminum in a mass ratio of 1:1 into a reverberatory furnace, controlling the melting temperature to 770°C, and removing slag during the melting process to obtain aluminum liquid;

[0085] (2) adding doping components to the aluminum liquid and performing composition control and cooling treatment, wherein the doping components include 3303 specification metal silicon, electrolytic manganese, pure magnesium ingot, aluminum-titanium alloy, aluminum-vanadium alloy, aluminum-molybdenum alloy and aluminum-zirconium alloy, and the cooling treatment includes air blowing cooling, with a target temperature of 720°C, and then adding Al-Ti-B alloy as a refiner for alloying;

[0086] (3) Add refining agent YHRJ1-2 to the aluminum liquid, perform refining and degassing at 720°C for 20 minutes, use nitrogen at an absolute pressure of 0.3 MPa, let it stand for more than 10 minutes after slagging and confirm the composition, then perform density equivalent test and slag content test to ensure that the density equivalent is ≤0.5% and the slag content K is ≤2 / 20;

[0087] (4) Aluminum strontium alloy is added to the aluminum liquid as a modifier, and the liquid is blown and stirred to form a soup, which is then die-casted. The temperature of the aluminum liquid is controlled to be 670°C, the clamping force of the die-casting machine is 4500 kN, and the thickness of the die-casting machine cake is 45 mm. The mold surface temperature is controlled by a mold temperature controller, and the mold temperature is set to 200°C, the casting pressure is 75 MPa, the injection time is 10 s, and the cooling time is 22 s. Among them, the punch stroke position during die-casting is: when the punch stroke reaches 100 mm, the speed is 0.2 m / s; when the punch stroke reaches 550 mm, the speed is 4.5 m / s; when the punch stroke reaches 670 mm, the pressurization is performed, and the pressurization value is 60% for 2 s, and finally a high-strength and high-toughness aluminum alloy is obtained.

[0088] In this preparation example, the air blowing and cooling in step (2), the refining and degassing in step (3), and the air blowing and stirring in step (4) are each independently performed using nitrogen, and the nitrogen is liquid nitrogen converted into gas at the smelting site and directly used in the corresponding process, and the purity of the obtained nitrogen is 5N grade.

[0089] Preparation Example 2

[0090] This preparation example is used to prepare the aluminum alloy described in Example 2, and the specific preparation method includes the following steps:

[0091] (1) Adding primary aluminum and recycled aluminum in a mass ratio of 1:0.5 into a reverberatory furnace, controlling the melting temperature to 760°C, and removing slag during the melting process to obtain aluminum liquid;

[0092] (2) adding doping components to the aluminum liquid and performing composition control and cooling treatment, wherein the doping components include 3303 specification metal silicon, electrolytic manganese, pure magnesium ingot, aluminum-titanium alloy, aluminum-vanadium alloy, aluminum-molybdenum alloy and aluminum-zirconium alloy, and the cooling treatment includes air blowing cooling, with a target temperature of 700° C., and then adding Al-Ti-B alloy as a refiner for alloying;

[0093] (3) Add refining agent YHRJ1-2 to the aluminum liquid, perform refining and degassing at 700°C for 30 minutes, use nitrogen at an absolute pressure of 0.25MPa, let it stand for more than 10 minutes after slagging and confirm the composition, then perform density equivalent test and slag content test to ensure that the density equivalent is ≤0.5% and the slag content K is ≤2 / 20;

[0094] (4) Aluminum strontium alloy is added to the aluminum liquid as a modifier, and the liquid is blown and stirred to form a soup, which is then die-casted. The temperature of the aluminum liquid is controlled to be 660°C, the clamping force of the die-casting machine is 4500 kN, and the thickness of the die-casting machine cake is 45 mm. The mold surface temperature is controlled by a mold temperature controller, and the mold temperature is set to 150°C, the casting pressure is 70 MPa, the injection time is 8 s, and the cooling time is 20 s. Among them, the punch stroke position during die-casting is: when the punch stroke reaches 100 mm, the speed is 0.2 m / s; when the punch stroke reaches 550 mm, the speed is 4.5 m / s; when the punch stroke reaches 670 mm, the pressurization is performed, and the pressurization value is 60% for 2 s, and finally a high-strength and high-toughness aluminum alloy is obtained.

[0095] In this preparation example, the air blowing and cooling in step (2), the refining and degassing in step (3), and the air blowing and stirring in step (4) are each independently performed using nitrogen, and the nitrogen is liquid nitrogen converted into gas at the smelting site and directly used in the corresponding process, and the purity of the obtained nitrogen is 5N5 grade.

[0096] Preparation Example 3

[0097] This preparation example is used to prepare the aluminum alloy described in Example 3. The specific preparation method includes the following steps:

[0098] (1) Adding primary aluminum and recycled aluminum in a mass ratio of 1:2 into a reverberatory furnace, controlling the melting temperature to 780°C, and removing slag during the melting process to obtain aluminum liquid;

[0099] (2) adding doping components to the aluminum liquid and performing composition control and cooling treatment, wherein the doping components include 3303 specification metal silicon, electrolytic manganese, pure magnesium ingot, aluminum-titanium alloy, aluminum-vanadium alloy, aluminum-molybdenum alloy and aluminum-zirconium alloy, and the cooling treatment includes air blowing cooling, with a target temperature of 740°C, and then adding Al-Ti-B alloy as a refiner for alloying;

[0100] (3) Add refining agent YHRJ1-2 to the aluminum liquid, perform refining and degassing at 740°C for 15 minutes, use nitrogen at an absolute pressure of 0.35 MPa, let it stand for more than 10 minutes after slagging and confirm the composition, then perform density equivalent test and slag content test to ensure that the density equivalent is ≤0.5% and the slag content K is ≤2 / 20;

[0101] (4) Aluminum strontium alloy is added to the aluminum liquid as a modifier, and the liquid is blown and stirred to form a soup, which is then die-casted. The temperature of the aluminum liquid is controlled to be 680°C, the clamping force of the die-casting machine is 4500 kN, and the thickness of the die-casting machine cake is 45 mm. The mold surface temperature is controlled by a mold temperature controller, and the mold temperature is set to 250°C, the casting pressure is 80 MPa, the injection time is 12 s, and the cooling time is 25 s. Among them, the punch stroke position during die-casting is: when the punch stroke reaches 100 mm, the speed is 0.2 m / s; when the punch stroke reaches 550 mm, the speed is 4.5 m / s; when the punch stroke reaches 670 mm, the pressurization is performed, and the pressurization value is 60% for 2 s, and finally a high-strength and high-toughness aluminum alloy is obtained.

[0102] In this preparation example, the air blowing and cooling in step (2), the refining and degassing in step (3), and the air blowing and stirring in step (4) are each independently performed using nitrogen, and the nitrogen is liquid nitrogen converted into gas at the smelting site and directly used in the corresponding process, and the purity of the obtained nitrogen is 6N grade.

[0103] Preparation Example 4-5

[0104] This group of preparation examples is used to prepare the aluminum alloys described in Examples 4-5 respectively. Except that the amount of each doping component added is adaptively adjusted according to the content of the constituent elements in Table 1, the remaining steps and conditions are the same as those in Preparation Example 1, so they are not repeated here.

[0105] Comparative Preparation Example 1-2

[0106] This group of comparative preparation examples is respectively used to prepare the aluminum alloys described in comparative examples 1-2. Except that the amount of each doping component added is adaptively adjusted according to the content of the constituent elements in Table 1, the remaining steps and conditions are the same as those in Preparation Example 1, so they are not repeated here.

[0107] Comparative Preparation Example 3

[0108] This comparative preparation example provides a method for preparing an aluminum alloy. Except that the air blowing and cooling in step (2), the refining and degassing in step (3), and the air blowing and stirring in step (4) are each independently performed using bottled nitrogen (with a purity of 3N grade), the remaining steps and conditions are the same as those in Preparation Example 1, and therefore are not described in detail here.

[0109] The aluminum alloy obtained in this comparative preparation 3 is defined as the aluminum alloy of comparative example 3.

[0110] Performance Testing

[0111] The yield strength, tensile strength and elongation of the aluminum alloys obtained in Examples 1-5 and Comparative Examples 1-3 were tested respectively, and the relevant test results are shown in Table 2 below.

[0112] Table 2

[0113]

[0114] In the above table, the yield strength, tensile strength and elongation tests refer to GB / T 228.1-2021.

[0115] Figure 1 The metallographic micrograph of the aluminum alloy cross section provided in Example 1, wherein the white area is the aluminum matrix and the black area is the grain boundary. The microstructure morphology of the aluminum alloy obtained in Examples 2-5 is similar to that in Example 1, so it will not be described here.

[0116] It can be seen that the aluminum alloy provided by the present invention uses low-cost elements and does not add high-cost trace elements such as rare earth. Through the matching mechanism between various elements and with the help of specific smelting conditions, a high-strength and high-toughness aluminum alloy that does not require heat treatment is finally produced, which fully meets the performance requirements of automotive structural parts and expands the application prospects of the material.

[0117] In addition, the present invention specifically limits the gas used for air blowing for cooling, refining degassing and air blowing stirring during the smelting process to high-purity nitrogen converted from liquid nitrogen at the smelting site, which has a better degassing effect and avoids the adverse effects of impurity elements in nitrogen on material properties.

[0118] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-strength and high-toughness aluminum alloy that does not require heat treatment, characterized in that: In terms of mass percentage, the constituent elements of the high-strength and high-toughness aluminum alloy include: Si 7%-8%; Fe ≤0.14%; Cu ≤0.008%; Mn 0.6%-0.7%; Mg 0.2%-0.26%; Zn ≤0.005%; Ca ≤0.001%; Pb ≤0.003%; Sb ≤0.0003%; Be ≤0.00008%; Ti 0.08%-0.15%; Mo 0.01%-0.08%; V 0.01%-0.08%； Zr 0.06%-0.25%； Sr 0.016%-0.026%； The balance is Al and inevitable impurities.

2. The high-strength and high-toughness aluminum alloy according to claim 1, characterized in that: In terms of mass percentage, the elements in the high-strength and high-toughness aluminum alloy satisfy: (Fe+Mn) / Zr≤10, and Mo+V≥0.04%; Measured by mass percentage, the impurities in the high-strength and high-toughness aluminum alloy satisfy the following requirements: the content of a single impurity is ≤0.05%, and the total amount of impurities is ≤0.15%.

3. The high-strength and high-toughness aluminum alloy according to claim 1 or 2, characterized in that: The high-strength and high-toughness aluminum alloy has a yield strength of ≥130 MPa, a tensile strength of ≥270 MPa, and an elongation of ≥10%.

4. A method for preparing the high-strength and high-toughness aluminum alloy according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: (1) Melting aluminum raw materials and removing slag during the melting process to obtain aluminum liquid; (2) adding doping components to the aluminum liquid and performing composition control and cooling treatment, wherein the cooling treatment includes air blowing cooling, and then adding a refiner for alloying; (3) Add refining agent to the aluminum liquid for refining and degassing, let it stand after slagging and confirm the composition; (4) Add a modifier to the aluminum liquid, blow air and stir it, and then get the liquid out. After die casting, a high-strength and high-toughness aluminum alloy is obtained; The air blowing and cooling in step (2), the refining and degassing in step (3) and the air blowing and stirring in step (4) are each independently carried out using nitrogen, and the nitrogen is liquid nitrogen converted into gas at the smelting site and directly used in the corresponding process, and the purity of the obtained nitrogen is ≥5N grade.

5. The preparation method according to claim 4, characterized in that: The melting in step (1) is carried out in a reverberatory furnace, and the melting temperature is 760-780°C; The aluminum raw material in step (1) includes primary aluminum and recycled aluminum, and the mass ratio of the primary aluminum to the recycled aluminum is 1:(0.5-2).

6. The preparation method according to claim 4 or 5, characterized in that: The doping components in step (2) include metallic silicon, electrolytic manganese, pure magnesium ingot, aluminum-titanium alloy, aluminum-vanadium alloy, aluminum-molybdenum alloy and aluminum-zirconium alloy; The target temperature of the cooling treatment in step (2) is 700-740°C; The refiner in step (2) includes Al-Ti-B alloy.

7. The preparation method according to any one of claims 4 to 6, characterized in that: The refining and degassing temperature in step (3) is 700-740°C and the time is 15-30 minutes; The absolute pressure of nitrogen used in the refining and degassing in step (3) is 0.25-0.35 MPa; The standing time in step (3) is ≥ 10 min; After the composition confirmation in step (3), the density equivalent test and slag content test are also included to ensure that the density equivalent is ≤0.5% and the slag content K is ≤2 / 20.

8. The preparation method according to any one of claims 4 to 7, characterized in that: The modifier in step (4) comprises an aluminum-strontium alloy; The blowing and stirring time in step (4) is ≤ 5 min; During the die casting in step (4), the temperature of the aluminum liquid is controlled to be 660-680°C, the temperature of the mold is controlled to be 150-250°C, the casting pressure is controlled to be 70-80MPa, the injection time is controlled to be 8-12s, and the cooling time is controlled to be 20-25s.

9. The preparation method according to any one of claims 4 to 8, characterized in that: The preparation method comprises the following steps: (1) Adding primary aluminum and recycled aluminum in a mass ratio of 1:(0.5-2) into a reverberatory furnace, controlling the melting temperature to 760-780°C, and removing slag during the melting process to obtain aluminum liquid; (2) adding doping components to the aluminum liquid and performing composition control and cooling treatment, wherein the doping components include metallic silicon, electrolytic manganese, pure magnesium ingot, aluminum-titanium alloy, aluminum-vanadium alloy, aluminum-molybdenum alloy and aluminum-zirconium alloy, and the cooling treatment includes air blowing cooling, with a target temperature of 700-740°C, and then adding Al-Ti-B alloy as a refiner for alloying; (3) Add refining agent to the aluminum liquid, and perform refining and degassing at 700-740℃ for 15-30min, using nitrogen at an absolute pressure of 0.25-0.35MPa. After slagging, let it stand for more than 10min and confirm the composition, then perform density equivalent test and slag content test to ensure that the density equivalent is ≤0.5% and the slag content K is ≤2 / 20; (4) Add aluminum strontium alloy as a modifier to the aluminum liquid, blow and stir it to get out the soup, and then perform die casting, and control the temperature of the aluminum liquid to 660-680°C, the temperature of the mold to 150-250°C, the casting pressure to 70-80MPa, the injection time to 8-12s, and the cooling time to 20-25s to obtain a high-strength and high-toughness aluminum alloy; The air blowing and cooling in step (2), the refining and degassing in step (3) and the air blowing and stirring in step (4) are each independently carried out using nitrogen, and the nitrogen is liquid nitrogen converted into gas at the smelting site and directly used in the corresponding process, and the purity of the obtained nitrogen is ≥5N grade.

10. An application of the high-strength and high-toughness aluminum alloy according to any one of claims 1 to 3, characterized in that: The high-strength and high-toughness aluminum alloy is used for manufacturing automobile structural parts.

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