Die-casting aluminum alloy capable of being anodized and preparation method thereof

Abstract

The invention provides a die-casting aluminum alloy capable of being anodized and a preparation method thereof. The die-casting aluminum alloy comprises the following elements in percentage by mass: 3.0-6.0 wt% of Zn, 0.3-2.0 wt% of Mg, less than or equal to 0.5 wt% of Cu, less than or equal to 0.5 wt% of Ti, less than or equal to 0.5 wt% of Sr, less than or equal to 0.5 wt% of Sc, less than or equal to 0.5 wt% of Zr and the balance of Al. According to the aluminum alloy, through selection of alloy elements such as Zn, Mg and Cu, the flowing property, the die-casting property and the mechanical property of the aluminum alloy are improved, then elements such as Ti, Sc, Zr and Sr are supplemented, internal stress and defects of the aluminum alloy are eliminated, grains are refined, the dispersion strengthening effect is achieved, the aluminum alloy can be prepared through die casting through selection of the elements and composition, the machining cost is greatly reduced, and the aluminum alloy is suitable for large-scale production. The production efficiency is improved, the mechanical property is excellent, and the strength and hardness are higher; the aluminum alloy is suitable for further anodic oxidation, and the coloring effect is good.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy materials and relates to an anodized die-casting aluminum alloy and a preparation method thereof. Background Art

[0002] Aluminum alloys are an important type of metal material. They are divided into different types according to their elemental composition. They are widely used in aerospace, aviation, transportation, construction, electromechanical, light chemical and daily necessities. According to different aluminum alloy processing methods, they can be divided into deformed aluminum alloys and cast aluminum alloys. Among them, die-cast aluminum alloys, as one of the cast aluminum alloys, can be used to produce products with complex structures and thin walls. However, aluminum alloy materials suitable for die-casting need to have good fluidity. Conventional aluminum alloys that can be used for die-casting are usually aluminum-silicon alloys. The high silicon content in the material gives it good fluidity. However, due to the high silicon content, flow marks may appear on the surface of aluminum-silicon alloys during anodizing, resulting in surface color difference, making them unsuitable for anodizing treatment, affecting their application range.

[0003] For the existing aluminum alloys suitable for anodizing, die-casting is usually not possible, but mechanical processing is required for production, such as the currently commonly used CNC machining center. For aluminum alloy products with more complex structures, this processing method has many processing steps and low processing efficiency, resulting in a long production process, high cost, and low material utilization. Therefore, it is necessary to improve the composition of the aluminum alloy to obtain an aluminum alloy material suitable for die-casting and can be used for color anodizing.

[0004] At present, although some anodized aluminum alloys that can be used for die casting are disclosed, their mechanical properties such as strength and hardness are relatively low, and the die casting fluidity is relatively poor, which increases the difficulty of die casting. CN 103526088A discloses a die casting aluminum alloy for digital electronic products, the chemical composition and proportion of the aluminum alloy include Zn 4.5-4.8wt%, Cu 1.8-2.0wt%, Mg 1.6-1.8wt%, Si 2.2-2.5wt%, Zr0.05-0.1%, Ni 0.4-0.6wt%, Ti0.5-1wt%, and the balance is aluminum and inevitable impurities; the preparation method of the aluminum alloy includes: raw material preparation, smelting, die casting, solution-quenching treatment, artificial aging and anodizing treatment. The silicon content in the aluminum alloy is still relatively high, and it can be prepared by die casting, but the difficulty of anodizing is relatively large, and it is easy to cause performance degradation, and there are many types of high-content elements, which are easy to cause performance conflicts.

[0005] CN 112481529A discloses an environmentally friendly die-cast aluminum alloy anodized film and its environmentally friendly preparation process. The die-cast aluminum alloy for anodization contains: Mg 3.0-6.0wt%, Zn 2.5-4.5wt%, Si 1.0-2.5wt%, Mn 0.5-1.0wt%, Cr 0.3-0.8%, and the balance is Al; the preparation method of the aluminum alloy includes: weighing raw materials according to mass ratio and then smelting to obtain molten metal, adding refining agent for refining, and stirring during the refining process; removing impurities from the refined molten metal and then casting to obtain an aluminum alloy ingot, melting the aluminum alloy ingot and then die-casting to obtain a die-cast aluminum alloy. The contents of Mg, Zn, and Si in the aluminum alloy are relatively high, and the role of each element and the specific operation of the die-casting process are not clarified. The focus is on the improvement of the anodized film process and the performance of the anodized film, and the performance after die-casting is not clarified.

[0006] In summary, for the selection of aluminum alloy components suitable for die casting and anodizing, it is necessary to select appropriate component ratios and preparation processes according to the characteristics of each element to ensure the mechanical properties of the die-casting aluminum alloy, reduce production costs, and improve production efficiency. Summary of the invention

[0007] In view of the problems existing in the prior art, the object of the present invention is to provide an anodizable die-casting aluminum alloy and a preparation method thereof. The aluminum alloy improves the flowability, die-casting performance and mechanical properties of the aluminum alloy by selecting alloying elements such as Zn, Mg, and Cu, and is supplemented with elements such as Ti, Sc, Zr, and Sr to eliminate the internal stress and defects of the aluminum alloy, refine the grains, play a dispersion strengthening role, and improve the coloring effect during anodizing, so that the aluminum alloy is suitable for die-casting preparation, has excellent mechanical properties, can be anodized, and has low production cost.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In one aspect, the present invention provides an anodizable die-casting aluminum alloy, wherein the element composition of the die-casting aluminum alloy comprises, by mass fraction, 3.0 to 6.0 wt% Zn, such as 3.0 wt%, 3.5 wt%, 4.0 wt%, 4.5 wt%, 5.0 wt%, 5.5 wt% or 6.0 wt%, etc., Mg 0.3-2.0wt%, for example, 0.3wt%, 0.5wt%, 0.8wt%, 1.0wt%, 1.2wt%, 1.5wt%, 1.8wt% or 2.0wt%, etc., Cu≤0.5wt%, for example, 0.5wt%, 0.45wt%, 0.4wt%, 0.35wt%, 0.3wt%, 0.25wt%, 0.2wt% or 0.1wt%, etc., Ti≤0.5wt%, for example, 0.5wt%, 0.45wt%, 0.4wt%, 0.35wt%, 0.3wt%, 0.25wt%, 0.2wt% or 0.1wt%, etc., Sr≤0.5wt%, for example, 0.5wt%, 0. %, 0.45wt%, 0.4wt%, 0.35wt%, 0.3wt%, 0.25wt%, 0.2wt% or 0.1wt%, etc., Sc≤0.5wt%, for example, 0.5wt%, 0.45wt%, 0.4wt%, 0.35wt%, 0.3wt%, 0.25wt%, 0.2wt% or 0.1wt%, etc., Zr≤0.5wt%, for example, 0.5wt%, 0.45wt%, 0.4wt%, 0.35wt%, 0.3wt%, 0.25wt%, 0.2wt% or 0.1wt%, etc., and the balance is Al; but are not limited to the listed values, and other unlisted values ​​within the respective numerical ranges are equally applicable.

[0010] In the present invention, according to the different elemental compositions of the aluminum alloy, its suitable preparation method and application direction will also be different. In order to obtain an aluminum alloy suitable for die casting and anodization, the present invention uses Zn and Mg as main alloying elements on the basis of Al, and improves the fluidity and die casting forming performance of the material after melting according to the characteristics of the two, while having high strength and hardness, and then improves the mechanical properties of the alloy material by adding Cu element, and then supplemented with Ti, Sr, Sc, Zr and other elements. Ti element can effectively refine the grains, eliminate defects, and improve uniformity. Sr element can form a stable mutual dissolution body with aluminum, so that the grain boundaries and dislocations of the aluminum alloy have a damping effect, thereby improving the strength, hardness and heat resistance of the alloy. Sc and Zr elements can also eliminate the inhomogeneity and residual stress of the alloy structure, and play a strengthening role. Through the selection of the above-mentioned element types and compositions, the aluminum alloy can be obtained by die casting, which greatly reduces the processing cost of the aluminum alloy, improves production efficiency, and has excellent mechanical properties, high strength and hardness, and can be further anodized to expand its application range.

[0011] The following are preferred technical solutions of the present invention, but are not intended to be limitations of the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0012] As a preferred technical solution of the present invention, the element composition in the die-cast aluminum alloy also includes Si≤0.06wt%, such as 0.06wt%, 0.05wt%, 0.04wt%, 0.03wt%, 0.02wt% or 0.01wt%, etc., Fe≤0.08wt%, such as 0.08wt%, 0.07wt%, 0.06wt%, 0.05wt%, 0.04wt%, 0.03wt%, 0.02wt% or 0.01wt%, etc., and inevitable impurities, but are not limited to the listed values, and other unlisted values ​​within the respective numerical ranges are equally applicable.

[0013] In the present invention, the Si content in the element composition of the aluminum alloy is extremely low. Although Si is the main component for improving fluidity and is suitable for die casting, it is not suitable for anodizing. Whether Si is distributed on the grain boundary or in the matrix, it will cause the aluminum oxide film to be uneven and incomplete. If it is distributed in the matrix, the oxide film thickness will be uneven. If it is distributed on the grain boundary, it will be mixed in the aluminum oxide film, causing the oxide film to be discontinuous. Therefore, it is necessary to reduce Si and select other elements that can improve the die casting performance.

[0014] The present invention also needs to control the iron content. Iron will generate hard and brittle Al6 (FeMn) phase in aluminum alloy, which will reduce the ductility and machinability of aluminum alloy, making it more fragile and brittle. In addition, although increasing the Fe content will reduce the mold sticking phenomenon to a certain extent, too high an iron content will cause the generated metal compounds to form hard spots, reducing the mechanical properties and casting quality.

[0015] On the other hand, the present invention provides a method for preparing the above die-cast aluminum alloy, the preparation method comprising the following steps:

[0016] (1) melting aluminum and removing slag, then adding preheated raw materials of various elements according to mass ratio for smelting to obtain a molten liquid;

[0017] (2) transferring the molten liquid obtained in step (1) to a mold for die casting to obtain a die casting;

[0018] (3) The die-casting obtained in step (2) is subjected to homogenization treatment and aging treatment in sequence to obtain a die-cast aluminum alloy.

[0019] As a preferred technical solution of the present invention, the purity of the aluminum element in step (1) is above 99.9%, for example, 99.9%, 99.91%, 99.92%, 99.93%, 99.94%, 99.95%, 99.96%, 99.97%, 99.98% or 99.99%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] Preferably, in step (1), the aluminum element is melted in a crucible, the crucible is cleaned before use, and the inside of the crucible is coated with aluminum oxide.

[0021] Preferably, the temperature for melting the aluminum element in step (1) is 750-800°C, for example, 750°C, 760°C, 770°C, 780°C, 790°C or 800°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] Preferably, in step (1), slag removal is performed by introducing an inert gas, wherein the inert gas includes helium, neon, argon, etc.

[0023] As a preferred technical solution of the present invention, among the raw materials of each element in step (1), Zn, Mg, and Cu are added in the form of simple substances, and Ti, Sr, Sc, and Zr are added in the form of alloys.

[0024] In the present invention, magnesium is a relatively active metal among the metals to be added to the aluminum liquid, and the protective cover needs to be completely immersed in the aluminum liquid to avoid oxidation resulting in unqualified components, wherein the protective cover can be made of silicon carbide material, which will not affect the composition of the aluminum liquid; magnesium can form a solid solution with aluminum to increase the lattice compactness and form a high-strength Mg2Al3 compound, which significantly improves the strength and rigidity of the aluminum alloy. The addition of magnesium can also increase the hardness of the aluminum alloy, but if the magnesium content is too high, the hardness will decrease instead. This is because the addition of magnesium will cause the grains to become finer, thereby causing the strength of the grain boundaries to decrease, and the toughness of the aluminum alloy will be affected.

[0025] Ti, Sr, Sc, and Zr are basically added in the form of alloys of the elements with aluminum, such as aluminum-titanium-boron wire, aluminum-strontium alloy, aluminum-scandium alloy, and aluminum-zirconium alloy.

[0026] Preferably, the preheating temperature of each element raw material in step (1) is independently 150-250°C, for example, 150°C, 160°C, 180°C, 200°C, 220°C, 240°C or 250°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] Preferably, the raw materials of each element in step (1) are added in batches in sequence, first adding Cu and Zn, then adding Mg, then adding Sc and Zr, and finally adding Ti and Sr.

[0028] In the present invention, in the order of adding the elements, the density of Cu and Zn is greater than that of Al and they sink to the bottom, while the density of Mg is less than that of Al and it floats on the aluminum liquid. The Sc and Zr elements are added together, mainly because the combination of scandium and zirconium can enhance the mechanical properties of the aluminum alloy. The addition of Ti and Sr has a time limit, and the aluminum liquid should be poured out within 30 minutes as much as possible, otherwise there will be no refinement and deterioration effects, so they are added last.

[0029] Preferably, the smelting temperature in step (1) is 700-770°C, for example 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C or 780°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] Preferably, after all the raw materials of each element in step (1) are melted, the composition of the melt is checked to see if it is qualified.

[0031] Preferably, the method for inspecting the composition of the melt includes OES testing.

[0032] As a preferred technical solution of the present invention, the molten liquid in step (2) is transferred to a die-casting mold for direct die-casting.

[0033] Preferably, the die-casting mold is preheated to 120-200°C, for example, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C or 200°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, and then the molten liquid is added to the cavity of the mold.

[0034] In the present invention, the die-casting mold is preheated to reduce the water vapor in the mold as much as possible to prevent air bubbles from being generated during die-casting.

[0035] Preferably, the flow rate of the molten liquid in the mold cavity is 50 to 180 mm / s, for example, 50 mm / s, 60 mm / s, 80 mm / s, 100 mm / s, 120 mm / s, 140 mm / s, 160 mm / s or 180 mm / s, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] Preferably, the die-casting pressure is 100-150 MPa, for example, 100 MPa, 110 MPa, 120 MPa, 130 MPa, 140 MPa or 150 MPa, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] In the present invention, the titanium element in the aluminum alloy is added in the form of aluminum-titanium-boron wire, which can refine the grains of pure aluminum and aluminum alloys and eliminate casting defects, thereby improving the mechanical properties of the products, such as improving the plasticity, mechanical properties and heat treatment effects of the products, and further enhancing the strength and toughness of the materials; it can also improve the surface quality of the products, such as improving the coloring effect and uniformity during subsequent anodizing.

[0038] As a preferred technical solution of the present invention, the molten liquid in step (2) is first transferred to a water-cooled mold for casting to obtain an aluminum alloy casting, and the aluminum alloy casting is then melted and die-casted.

[0039] Preferably, the molten liquid is cast into a water-cooled mold to be condensed and solidified, and a cooling water channel is provided in the water-cooled mold.

[0040] Preferably, the molten liquid casting rate is 10 to 50 mm / s, for example, 10 mm / s, 15 mm / s, 20 mm / s, 25 mm / s, 30 mm / s, 35 mm / s, 40 mm / s, 45 mm / s or 50 mm / s, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0041] Preferably, the cooling rate of the molten liquid before condensation and solidification is 1 to 10°C / min, for example, 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 8°C / min or 10°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable; the cooling rate after condensation and solidification is 1 to 10°C / min, for example, 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 8°C / min or 10°C / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable.

[0042] Preferably, the molten liquid is removed from the water-cooled mold after condensation and solidification, and is melted again and die-casted using the die-casting mold.

[0043] In the present invention, the aluminum alloy melt can be first cast to obtain a casting, and then melted again for die casting. This is mainly for the convenience of making castings first for transportation when the melting process and the die casting process are not in the same place and cannot be operated continuously.

[0044] As a preferred technical solution of the present invention, the temperature of the homogenization treatment in step (3) is 350-550°C, for example, 350°C, 380°C, 400°C, 420°C, 450°C, 480°C, 500°C, 520°C or 550°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] Preferably, the homogenization treatment time in step (3) is 1 to 12 hours, for example, 1 hour, 2 hours, 4 hours, 6 hours, 8 hours, 10 hours or 12 hours, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] In the present invention, the copper in the aluminum alloy is mainly dissolved in the aluminum matrix, plays a solid solution strengthening role, and can improve the corrosion resistance of the aluminum alloy.

[0047] The purpose of homogenization treatment of aluminum alloys containing Sc and Zr elements is to eliminate the inhomogeneity of alloy structure and composition, eliminate the residual stress generated during non-equilibrium solidification, and precipitate nanometer-scale secondary Al (Sc, Zr) particles from the supersaturated solid solution to play a role in dispersion strengthening.

[0048] Preferably, the homogenization treatment in step (3) is followed by water cooling to lower the temperature to room temperature.

[0049] In the present invention, when the aluminum alloy is die-cast, the melt cools quickly and is basically close to a supersaturated solid solution. There are low-melting-point non-equilibrium phases rich in Zn and Mg at the grain boundaries. The ingot needs to be homogenized. During the homogenization process, on the one hand, the low-melting-point non-equilibrium phases rich in Zn and Mg in the grain boundary region are gradually dissolved into the matrix, and on the other hand, the supersaturated solid solution decomposes and precipitates non-equilibrium phases. As the homogenization temperature increases, the precipitated non-equilibrium phases will dissolve back into the matrix again.

[0050] As a preferred technical solution of the present invention, the temperature of the aging treatment in step (3) is 100-150°C, for example, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0051] Preferably, the aging treatment time in step (3) is 12 to 24 hours, for example, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0052] Preferably, the aging treatment in step (3) is followed by natural cooling to room temperature.

[0053] Based on the above description of the role of zinc, in addition to providing die-casting performance and mechanical properties, it also has a good natural aging strengthening effect, making die-cast products suitable for application scenarios with relatively high expected strength.

[0054] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0055] (1) melting aluminum and removing slag, wherein the purity of the aluminum is above 99.9%, and melting is performed in a crucible, which is cleaned before use and coated with alumina inside the crucible; the temperature of the aluminum melting is 750-800°C, and the slag is removed by introducing an inert gas, and then the preheated raw materials of various elements are added according to the mass ratio for smelting, wherein Zn, Mg, and Cu are added in the form of single substances, and Ti, Sr, Sc, and Zr are added in the form of alloys, and the preheating temperature is independently 150-250°C, and the raw materials of various elements are added in batches in sequence, first adding Cu and Zn, then adding Mg, then adding Sc and Zr, and finally adding Ti and Sr, and the smelting temperature is 700-770°C to obtain a molten liquid, and checking whether the composition of the molten liquid is qualified, and the inspection method includes OES testing;

[0056] (2) transferring the molten liquid obtained in step (1) to a die-casting mold for direct die-casting, wherein the die-casting mold is preheated to 120-200° C., and then adding the molten liquid into the mold cavity, wherein the flow rate of the molten liquid in the mold cavity is 50-180 mm / s, and the pressure of the die-casting is 100-150 MPa; or the molten liquid is first transferred to a water-cooled mold for casting to obtain an aluminum alloy casting, wherein the molten liquid is cast into the water-cooled mold for condensation and solidification, wherein a cooling water channel is provided in the water-cooled mold, wherein the cooling rate of the molten liquid before condensation and solidification is 1-10° C. / min, and the cooling rate after condensation and solidification is 1-10° C. / min, and the casting rate of the molten liquid is 10-50 mm / s, wherein the molten liquid is removed from the water-cooled mold after condensation and solidification, and is melted again for die-casting using the die-casting mold to obtain a die-casting;

[0057] (3) The die casting obtained in step (2) is subjected to homogenization treatment and aging treatment in sequence, wherein the temperature of the homogenization treatment is 350-550° C. and the time is 1-12 h. After the homogenization treatment, the die casting is water-cooled to room temperature. The temperature of the aging treatment is 100-150° C. and the time is 12-24 h. The die casting is naturally cooled to room temperature to obtain a die-cast aluminum alloy.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] (1) The aluminum alloy of the present invention improves the flowability, die-casting performance and mechanical properties of the aluminum alloy by selecting alloying elements such as Zn, Mg and Cu, and is supplemented by elements such as Ti, Sc, Zr and Sr to eliminate the internal stress and defects of the aluminum alloy, refine the grains, and play a role in dispersion strengthening;

[0060] (2) The present invention selects the type and composition of aluminum alloy elements so that the aluminum alloy can be made by die casting, which greatly reduces the processing cost of the aluminum alloy and improves production efficiency. The aluminum alloy has excellent mechanical properties, high strength and hardness, a tensile strength of more than 350 MPa, a yield strength of more than 300 MPa, a hardness of more than 110 HB, and an elongation of more than 4%.

[0061] (3) The die-cast aluminum alloy of the present invention is suitable for further anodization, has good coloring effect, and has a wider application field. DETAILED DESCRIPTION

[0062] In order to better illustrate the present invention and facilitate understanding of the technical solution of the present invention, the present invention is further described in detail below. However, the following embodiments are only simple examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0063] The specific implementation method of the present invention provides an anodizable die-cast aluminum alloy and a preparation method thereof. The element composition of the die-cast aluminum alloy includes, by mass fraction, 3.0-6.0wt% Zn, 0.3-2.0wt% Mg, ≤0.5wt% Cu, ≤0.5wt% Ti, ≤0.5wt% Sr, ≤0.5wt%, Sc≤0.5wt%, Zr≤0.5wt%, and the balance is Al.

[0064] The preparation method comprises the following steps:

[0065] (1) melting aluminum and removing slag, then adding preheated raw materials of various elements according to mass ratio for smelting to obtain a molten liquid;

[0066] (2) transferring the molten liquid obtained in step (1) to a mold for die casting to obtain a die casting;

[0067] (3) The die-casting obtained in step (2) is subjected to homogenization treatment and aging treatment in sequence to obtain a die-cast aluminum alloy.

[0068] The following are typical but non-limiting embodiments of the present invention:

[0069] Embodiment 1:

[0070] The present embodiment provides an anodizable die-cast aluminum alloy and a preparation method thereof. The element composition of the die-cast aluminum alloy comprises, by mass fraction, 4.5wt% Zn, 1.0wt% Mg, 0.5wt% Cu, 0.3wt% Ti, 0.3wt% Sr, 0.4wt% Sc, 0.4wt% Zr, and the balance is Al.

[0071] The element composition of the die-casting aluminum alloy further includes 0.05wt% Si, 0.06wt% Fe and inevitable impurities.

[0072] The preparation method comprises the following steps:

[0073] (1) melting aluminum and removing slag, wherein the purity of the aluminum is 99.95%, and a crucible is used for melting, and the crucible is cleaned before use, and alumina is coated inside the crucible; the melting temperature of the aluminum is 780°C, and argon is introduced to remove slag, and then the preheated raw materials of each element are added according to the mass ratio for smelting, wherein Zn, Mg, and Cu are added in the form of single substances, and Ti, Sr, Sc, and Zr are added in the form of alloys, and the preheating temperature is independently 200°C, and the raw materials of each element are added in batches in sequence, first adding Cu and Zn, then adding Mg, then adding Sc and Zr, and finally adding Ti and Sr, and the melting temperature is 750°C to obtain a molten liquid, and after checking that the composition of the molten liquid is qualified, the next step is carried out, and the inspection method is OES test;

[0074] (2) transferring the molten liquid obtained in step (1) to a die-casting mold for direct die-casting, wherein the die-casting mold is preheated to 150° C., and then adding the molten liquid into the mold cavity of the mold, wherein the flow rate of the molten liquid in the mold cavity is 100 mm / s, and the die-casting pressure is 120 MPa, to obtain a die-casting;

[0075] (3) The die casting obtained in step (2) is subjected to homogenization treatment and aging treatment in sequence, wherein the temperature of the homogenization treatment is 450° C. and the time is 6 h. After the homogenization treatment, the die casting is water-cooled to room temperature. The temperature of the aging treatment is 120° C. and the time is 18 h. The die casting is naturally cooled to room temperature to obtain a die-cast aluminum alloy.

[0076] In this embodiment, according to the selection of the above-mentioned aluminum alloy components, a die-casting method can be used for preparation. The obtained die-cast aluminum alloy has a tensile strength of 375 MPa, a yield strength of 320 MPa, a Brinell hardness of 118 HB, an elongation of 4.7%, and a good coloring effect after anodizing.

[0077] Embodiment 2:

[0078] The present embodiment provides an anodizable die-cast aluminum alloy and a preparation method thereof. The element composition of the die-cast aluminum alloy comprises, by mass fraction, 6.0wt% Zn, 0.3wt% Mg, 0.4wt% Cu, 0.5wt% Ti, 0.5wt% Sr, 0.3wt% Sc, 0.3wt% Zr, and the balance is Al.

[0079] The element composition of the die-casting aluminum alloy further includes 0.06wt% Si, 0.05wt% Fe and inevitable impurities.

[0080] The preparation method comprises the following steps:

[0081] (1) melting aluminum and removing slag, wherein the purity of the aluminum is 99.92%, and a crucible is used for melting, and the crucible is cleaned before use, and alumina is coated inside the crucible; the temperature of the aluminum melting is 750°C, and argon is introduced to remove slag, and then the preheated raw materials of each element are added according to the mass ratio for smelting, wherein Zn, Mg, and Cu are added in the form of single substances, and Ti, Sr, Sc, and Zr are added in the form of alloys, and the preheating temperature is independently 150°C, and the raw materials of each element are added in batches in sequence, first adding Cu and Zn, then adding Mg, then adding Sc and Zr, and finally adding Ti and Sr, and the melting temperature is 700°C to obtain a molten liquid, and after checking that the composition of the molten liquid is qualified, the next step is carried out, and the inspection method is OES test;

[0082] (2) transferring the molten liquid obtained in step (1) to a die-casting mold for direct die-casting, wherein the die-casting mold is preheated to 120° C., and then adding the molten liquid into the mold cavity of the mold, wherein the flow rate of the molten liquid in the mold cavity is 60 mm / s, and the die-casting pressure is 100 MPa, to obtain a die-casting;

[0083] (3) The die casting obtained in step (2) is subjected to homogenization treatment and aging treatment in sequence, wherein the temperature of the homogenization treatment is 350° C. and the time is 12 h. After the homogenization treatment, the die casting is water-cooled to room temperature. The temperature of the aging treatment is 100° C. and the time is 24 h. The die casting is naturally cooled to room temperature to obtain a die-cast aluminum alloy.

[0084] In this embodiment, according to the selection of the above-mentioned aluminum alloy components, a die-casting method can be used for preparation. The obtained die-cast aluminum alloy has a tensile strength of 368 MPa, a yield strength of 315 MPa, a Brinell hardness of 115 HB, an elongation of 4.5%, and a good coloring effect after anodizing.

[0085] Embodiment 3:

[0086] The present embodiment provides an anodizable die-cast aluminum alloy and a preparation method thereof. The element composition of the die-cast aluminum alloy comprises, by mass fraction, 3.0wt% Zn, 2.0wt% Mg, 0.3wt% Cu, 0.4wt% Ti, 0.4wt% Sr, 0.5wt% Sc, 0.5wt% Zr, and the balance is Al.

[0087] The element composition of the die-casting aluminum alloy further includes 0.04wt% Si, 0.08wt% Fe and inevitable impurities.

[0088] The preparation method comprises the following steps:

[0089] (1) melting aluminum and removing slag, wherein the purity of the aluminum is 99.98%, and a crucible is used for melting, and the crucible is cleaned before use, and alumina is coated inside the crucible; the temperature of the aluminum melting is 800°C, and argon is introduced to remove slag, and then the preheated raw materials of each element are added according to the mass ratio for smelting, wherein Zn, Mg, and Cu are added in the form of single substances, and Ti, Sr, Sc, and Zr are added in the form of alloys, and the preheating temperature is independently 250°C. The raw materials of each element are added in batches in sequence, first adding Cu and Zn, then adding Mg, then adding Sc and Zr, and finally adding Ti and Sr, and the melting temperature is 770°C to obtain a molten liquid, and after checking that the composition of the molten liquid is qualified, the next step is carried out, and the inspection method is OES test;

[0090] (2) The molten liquid obtained in step (1) is first transferred to a water-cooled mold for casting to obtain an aluminum alloy casting, the molten liquid is cast into the water-cooled mold for condensation and solidification, the water-cooled mold is provided with a cooling water channel, the molten liquid casting rate is 40 mm / s, the cooling rate of the molten liquid before condensation and solidification is 5°C / min, and the cooling rate after condensation and solidification is 7°C / min, the molten liquid is removed from the water-cooled mold after condensation and solidification, and is melted again and die-casted using a die-casting mold, the die-casting mold is first preheated to 200°C, and then the molten liquid is added to the mold cavity, the flow rate of the molten liquid in the mold cavity is 150 m / s, and the pressure of the die-casting is 150 MPa to obtain a die-casting;

[0091] (3) The die casting obtained in step (2) is subjected to homogenization treatment and aging treatment in sequence, wherein the homogenization treatment is performed at a temperature of 550° C. and a time of 2 h, the homogenization treatment is water-cooled to a room temperature, the aging treatment is performed at a temperature of 150° C. and a time of 12 h, and the die casting is naturally cooled to a room temperature to obtain a die-cast aluminum alloy.

[0092] In this embodiment, according to the selection of the above-mentioned aluminum alloy components, a die-casting method can be used for preparation. The obtained die-cast aluminum alloy has a tensile strength of 365 MPa, a yield strength of 312 MPa, a Brinell hardness of 116 HB, an elongation of 4.3%, and a good coloring effect after anodizing.

[0093] Embodiment 4:

[0094] The present embodiment provides an anodizable die-cast aluminum alloy and a preparation method thereof. The element composition of the die-cast aluminum alloy comprises, by mass fraction, 4.0wt% Zn, 1.5wt% Mg, 0.2wt% Cu, 0.35wt% Ti, 0.45wt% Sr, 0.25wt% Sc, 0.25wt% Zr, and the balance is Al.

[0095] The element composition of the die-casting aluminum alloy further includes 0.03wt% Si, 0.07wt% Fe and inevitable impurities.

[0096] The preparation method comprises the following steps:

[0097] (1) melting aluminum and removing slag, wherein the purity of the aluminum is 99.9%, and a crucible is used for melting. The crucible is cleaned before use and coated with alumina inside the crucible. The melting temperature of the aluminum is 760°C, and argon is introduced to remove slag. Then, the preheated raw materials of various elements are added according to the mass ratio for smelting. Among the raw materials of various elements, Zn, Mg, and Cu are added in the form of simple substances, and Ti, Sr, Sc, and Zr are added in the form of alloys. The preheating temperature is independently 180°C. The raw materials of various elements are added in batches in sequence, first adding Cu and Zn, then adding Mg, then adding Sc and Zr, and finally adding Ti and Sr. The melting temperature is 720°C to obtain a molten liquid. After checking that the composition of the molten liquid is qualified, the next step is carried out. The inspection method is OES test;

[0098] (2) transferring the molten liquid obtained in step (1) to a die-casting mold for direct die-casting, wherein the die-casting mold is preheated to 140° C., and then adding the molten liquid into the mold cavity of the mold, wherein the flow rate of the molten liquid in the mold cavity is 80 mm / s, and the die-casting pressure is 110 MPa, to obtain a die-casting;

[0099] (3) The die casting obtained in step (2) is subjected to homogenization treatment and aging treatment in sequence, wherein the temperature of the homogenization treatment is 500° C. and the time is 10 h. After the homogenization treatment, the die casting is water-cooled to room temperature. The temperature of the aging treatment is 140° C. and the time is 20 h. The die casting is naturally cooled to room temperature to obtain a die-cast aluminum alloy.

[0100] In this embodiment, according to the selection of the above-mentioned aluminum alloy components, a die-casting method can be used for preparation. The obtained die-cast aluminum alloy has a tensile strength of 357 MPa, a yield strength of 310 MPa, a Brinell hardness of 112 HB, an elongation of 4.2%, and a good coloring effect after anodizing.

[0101] Embodiment 5:

[0102] The present embodiment provides an anodizable die-cast aluminum alloy and a preparation method thereof. The element composition of the die-cast aluminum alloy comprises, by mass fraction, 5.0wt% Zn, 0.7wt% Mg, 0.35wt% Cu, 0.2wt% Ti, 0.4wt% Sr, 0.45wt% Sc, 0.35wt% Zr, and the balance is Al.

[0103] The element composition of the die-casting aluminum alloy further includes 0.05wt% Si, 0.04wt% Fe and inevitable impurities.

[0104] The preparation method comprises the following steps:

[0105] (1) melting aluminum and removing slag, the purity of the aluminum is 99.92%, and melting is carried out in a crucible, the crucible is cleaned before use, and alumina is coated inside the crucible; the melting temperature of the aluminum is 790°C, argon is introduced to remove slag, and then the preheated raw materials of each element are added according to the mass ratio for smelting, among which Zn, Mg, and Cu are added in the form of single substances, and Ti, Sr, Sc, and Zr are added in the form of alloys, and the preheating temperature is independently 220°C. The raw materials of each element are added in batches in sequence, first adding Cu and Zn, then adding Mg, then adding Sc and Zr, and finally adding Ti and Sr, and the melting temperature is 760°C to obtain a molten liquid, and after checking that the composition of the molten liquid is qualified, the next step is carried out, and the inspection method is OES test;

[0106] (2) The molten liquid obtained in step (1) is first transferred to a water-cooled mold for casting to obtain an aluminum alloy casting, the molten liquid is cast into the water-cooled mold for condensation and solidification, the water-cooled mold is provided with a cooling water channel, the molten liquid casting rate is 20 mm / s, the cooling rate of the molten liquid before condensation and solidification is 3°C / min, and the cooling rate after condensation and solidification is 5°C / min, the molten liquid is removed from the water-cooled mold after condensation and solidification, and is melted again and die-casted using a die-casting mold, the die-casting mold is first preheated to 180°C, and then the molten liquid is added to the mold cavity, the flow rate of the molten liquid in the mold cavity is 120 mm / s, and the pressure of the die-casting is 135 MPa to obtain a die-casting;

[0107] (3) The die casting obtained in step (2) is subjected to homogenization treatment and aging treatment in sequence, wherein the temperature of the homogenization treatment is 400° C. and the time is 5 h. After the homogenization treatment, the die casting is water-cooled to room temperature. The temperature of the aging treatment is 130° C. and the time is 16 h. The die casting is naturally cooled to room temperature to obtain a die-cast aluminum alloy.

[0108] In this embodiment, according to the selection of the above-mentioned aluminum alloy components, a die-casting method can be used for preparation. The obtained die-cast aluminum alloy has a tensile strength of 360 MPa, a yield strength of 308 MPa, a Brinell hardness of 116 HB, an elongation of 4.4%, and a good coloring effect after anodizing.

[0109] Comparative Example 1:

[0110] This comparative example provides an anodizable die-cast aluminum alloy, the elemental composition of the die-cast aluminum alloy refers to the elemental composition in Example 1, except that the Zn content is 2.0 wt %, and the reduced Zn content is added to the Al content.

[0111] Comparative Example 2:

[0112] This comparative example provides an anodizable die-cast aluminum alloy, the elemental composition of the die-cast aluminum alloy refers to the elemental composition in Example 1, except that the Zn content is 7.5 wt %, and the increased Zn content is provided by reducing the Al content.

[0113] In Comparative Examples 1 and 2, when the zinc content is too low, the mechanical properties of the aluminum alloy do not meet the requirements, and the tensile strength is about 300 MPa and the hardness is about 60 HB; when the zinc content is too high, zinc segregation is likely to occur after die casting, resulting in uneven color after anodizing.

[0114] Comparative Example 3:

[0115] This comparative example provides an anodizable die-cast aluminum alloy, the elemental composition of the die-cast aluminum alloy refers to the elemental composition in Example 1, except that the Mg content is 2.5 wt %, and the increased Mg content is provided by reducing the Al content.

[0116] Comparative Example 4:

[0117] This comparative example provides an anodizable die-cast aluminum alloy, the elemental composition of which refers to the elemental composition in Example 1, except that the Mg content is 0.2 wt %, and the reduced Mg content is added to the Al content.

[0118] In Comparative Examples 3 and 4, based on the role of metallic magnesium in aluminum alloys, when the magnesium content is too low, the improvement in the performance of the aluminum alloy is very limited. At this time, the strength and rigidity of the aluminum alloy are reduced, and the tensile strength is about 315 MPa, but the ductility and toughness are improved, and the elongation reaches about 5.0%. At the same time, there is a tendency of stress corrosion cracking; when the magnesium content is too high, the grain size in the aluminum alloy becomes smaller, resulting in a decrease in the plasticity and toughness of the aluminum alloy, and cracks are easily generated. At this time, the elongation is about 3.2%, and the hardness is reduced to about 98 HB.

[0119] It can be seen from the above embodiments and comparative examples that the aluminum alloy of the present invention improves the flowability, die-casting performance and mechanical properties of the aluminum alloy by selecting alloying elements such as Zn, Mg, and Cu, and is supplemented by elements such as Ti, Sc, Zr, and Sr to eliminate the internal stress and defects of the aluminum alloy, refine the grains, and play a role in dispersion strengthening; by selecting the type and composition of aluminum alloy elements, the aluminum alloy can be obtained by die casting, which greatly reduces the processing cost of the aluminum alloy and improves production efficiency, and has excellent mechanical properties, high strength and hardness, a tensile strength of more than 350MPa, a yield strength of more than 300MPa, a hardness of more than 110HB, and an elongation of more than 4%; the die-cast aluminum alloy is suitable for further anodizing, has a good coloring effect, and has a wider range of applications.

[0120] The applicant declares that the present invention uses the above embodiments to illustrate the detailed products and methods of the present invention, but the present invention is not limited to the above detailed products and methods, that is, it does not mean that the present invention must rely on the above detailed products and methods to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. An anodizable die-cast aluminum alloy, characterized in that: The element composition of the die-casting aluminum alloy includes, by mass fraction, 3.0-6.0wt% Zn, 0.3-2.0wt% Mg, Cu≤0.5wt%, Ti≤0.5wt%, Sr≤0.5wt%, Sc≤0.5wt%, Zr≤0.5wt%, and the balance is Al.

2. The die-cast aluminum alloy according to claim 1, characterized in that: The element composition of the die-casting aluminum alloy also includes Si≤0.06wt%, Fe≤0.08wt% and inevitable impurities.

3. The method for preparing a die-cast aluminum alloy according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: (1) melting aluminum and removing slag, then adding preheated raw materials of various elements according to mass ratio for smelting to obtain a molten liquid; (2) transferring the molten liquid obtained in step (1) to a mold for die casting to obtain a die casting; (3) The die-casting obtained in step (2) is subjected to homogenization treatment and aging treatment in sequence to obtain a die-cast aluminum alloy.

4. The preparation method according to claim 3, characterized in that: The purity of the aluminum element in step (1) is above 99.9%; Preferably, the aluminum element in step (1) is melted in a crucible, the crucible is cleaned before use, and the inside of the crucible is coated with aluminum oxide; Preferably, the temperature of melting the aluminum element in step (1) is 750-800°C; Preferably, in step (1), slag removal is performed by introducing an inert gas.

5. The preparation method according to claim 3 or 4, characterized in that: Among the raw materials of each element in step (1), Zn, Mg, and Cu are added in the form of single substances, and Ti, Sr, Sc, and Zr are added in the form of alloys; Preferably, the preheating temperature of each element raw material in step (1) is independently 150-250°C; Preferably, the raw materials of each element in step (1) are added in batches in sequence, first adding Cu and Zn, then adding Mg, then adding Sc and Zr, and finally adding Ti and Sr; Preferably, the smelting temperature in step (1) is 700-770°C; Preferably, after all the raw materials of each element in step (1) are melted, check whether the composition of the melt is qualified; Preferably, the method for inspecting the composition of the melt includes OES testing.

6. The preparation method according to any one of claims 3 to 5, characterized in that: The molten liquid in step (2) is transferred to a die-casting mold for direct die-casting; Preferably, the die casting mold is preheated to 120-200° C., and then the molten liquid is added into the mold cavity; Preferably, the flow rate of the molten liquid in the mold cavity is 50 to 180 mm / s; Preferably, the die-casting pressure is 100-150 MPa.

7. The preparation method according to any one of claims 3 to 6, characterized in that: The molten liquid in step (2) is first transferred to a water-cooled mold for casting to obtain an aluminum alloy casting, and the aluminum alloy casting is then melted and die-casted; Preferably, the molten liquid is cast into a water-cooled mold for condensation and solidification, and a cooling water channel is provided in the water-cooled mold; Preferably, the casting rate of the molten liquid is 10 to 50 mm / s; Preferably, the cooling rate of the molten liquid before condensation and solidification is 1 to 10°C / min, and the cooling rate of the molten liquid after condensation and solidification is 1 to 10°C / min; Preferably, the molten liquid is removed from the water-cooled mold after condensation and solidification, and is melted again and die-casted using the die-casting mold.

8. The preparation method according to any one of claims 3 to 7, characterized in that: The temperature of the homogenization treatment in step (3) is 350-550° C. Preferably, the homogenization treatment time in step (3) is 1 to 12 hours; Preferably, the homogenization treatment in step (3) is followed by water cooling to lower the temperature to room temperature.

9. The preparation method according to any one of claims 3 to 8, characterized in that: The temperature of the aging treatment in step (3) is 100-150°C; Preferably, the aging treatment time in step (3) is 12 to 24 hours; Preferably, the aging treatment in step (3) is followed by natural cooling to room temperature.

10. The preparation method according to any one of claims 3 to 9, characterized in that: The preparation method comprises the following steps: (1) melting aluminum and removing slag, wherein the purity of the aluminum is above 99.9%, and melting is performed in a crucible, which is cleaned before use and coated with alumina inside the crucible; the temperature of the aluminum melting is 750-800°C, and the slag is removed by introducing an inert gas, and then the preheated raw materials of various elements are added according to the mass ratio for smelting, wherein Zn, Mg, and Cu are added in the form of single substances, and Ti, Sr, Sc, and Zr are added in the form of alloys, and the preheating temperature is independently 150-250°C, and the raw materials of various elements are added in batches in sequence, first adding Cu and Zn, then adding Mg, then adding Sc and Zr, and finally adding Ti and Sr, and the smelting temperature is 700-770°C to obtain a molten liquid, and checking whether the composition of the molten liquid is qualified, and the inspection method includes OES testing; (2) transferring the molten liquid obtained in step (1) to a die-casting mold for direct die-casting, wherein the die-casting mold is preheated to 120-200° C., and then adding the molten liquid into the mold cavity, wherein the flow rate of the molten liquid in the mold cavity is 50-180 mm / s, and the pressure of the die-casting is 100-150 MPa; or the molten liquid is first transferred to a water-cooled mold for casting to obtain an aluminum alloy casting, wherein the molten liquid is cast into the water-cooled mold for condensation and solidification, wherein a cooling water channel is provided in the water-cooled mold, wherein the casting rate of the molten liquid is 10-50 mm / s, wherein the cooling rate of the molten liquid before condensation and solidification is 1-10° C. / min, and the cooling rate after condensation and solidification is 1-10° C. / min, wherein the molten liquid is removed from the water-cooled mold after condensation and solidification, and then melted again for die-casting using the die-casting mold to obtain a die-casting; (3) The die casting obtained in step (2) is subjected to homogenization treatment and aging treatment in sequence, wherein the temperature of the homogenization treatment is 350-550° C. and the time is 1-12 h. After the homogenization treatment, the die casting is water-cooled to room temperature. The temperature of the aging treatment is 100-150° C. and the time is 12-24 h. The die casting is naturally cooled to room temperature to obtain a die-cast aluminum alloy.