Anodic oxidation die-casting aluminum alloy and preparation method thereof

Abstract

The invention provides an anodic oxidation die-casting aluminum alloy and a preparation method thereof. The anodic oxidation die-casting aluminum alloy comprises the following elements in percentage by mass: 2-4% of Mg element, 0.2-2% of Si element, 1.6-2.4% of Mn element, 0.2-0.3% of Cu element, less than or equal to 2% of Zn element, less than or equal to 0.2% of Fe element, less than or equal to 0.2% of inevitable impurities and the balance of Al, wherein the sum of the mass content of the Mg element and the mass content of the Zn element is 2-4%; the surface chromatic aberration of the anodic oxidation die-casting aluminum alloy is lt; the white brightness L is larger than or equal to 85, the tensile strength ranges from 180 MPa to 210 MPa, the yield strength ranges from 80 MPa to 120 MPa, and the elongation ranges from 3% to 5%. The anodic oxidation die-casting aluminum alloy has excellent flowability and surface glossiness, and is good in surface quality and high in yield.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and in particular to an anodized die-casting aluminum alloy and a preparation method thereof. Background Art

[0002] There are many types of 3C products, including mobile phone frames, headphones, smart wearables and wireless headphone shells. Due to the high requirements for the use and appearance of 3C products, anodizing treatment is required in the process of obtaining 3C products. Currently, 5xxx and 6xxx aluminum alloy products are mainly used. However, the price of deformed alloys is high and the shape is single. When producing products with complex structures, a lot of CNC processing is required, which is time-consuming and labor-intensive, and wastes a lot of materials.

[0003] At the same time, the current anodized die-casting alloys have the problem of difficulty in balancing fluidity and surface gloss. Many products with thin walls, such as wireless headset shells, have a wall thickness of about 1.5 mm, which is difficult to form using anodized die-casting alloys. In die-casting alloys, the fluidity of the alloy is generally improved by adding an appropriate amount of Si element, but the addition of Si element will cause the fluidity of anodized die-casting alloys to be lower than that of conventional Al-Si die-casting alloys.

[0004] The Chinese patent with patent application announcement number CN115522104B provides an anodized die-casting alloy, which improves the fluidity of the alloy by adding an appropriate amount of Si element to a content of 2-7%, but this method easily makes the surface dark after anodization. At the same time, part of the Al-Si eutectic phase will be exposed on the surface layer of the die-casting, and black spot defects are likely to appear near this position after anodization, resulting in reduced surface quality and yield of the die-casting, and poor surface gloss of the die-casting, which makes it difficult for the synthesized die-casting to be used in 3C products with high surface quality requirements. Summary of the invention

[0005] The main purpose of the present invention is to provide an anodized die-cast aluminum alloy and a preparation method thereof, so as to solve the problems in the prior art that the anodized die-cast aluminum alloy is difficult to achieve both excellent fluidity and surface gloss, and the anodized die-cast aluminum alloy has poor surface quality and low yield.

[0006] In order to achieve the above-mentioned object, according to one aspect of the present invention, there is provided an anodized die-casting aluminum alloy, which comprises the following elements, in percentage by mass: 2-4% of Mg, 0.2-2% of Si, 1.6-2.4% of Mn, 0.2-0.3% of Cu, ≤2% of Zn and ≤0.2% of Fe, the total content of inevitable impurities is ≤0.2%, and the balance is Al; wherein the sum of the mass contents of Mg and Zn is 2-4%; the surface color difference of the anodized die-casting aluminum alloy is <0.3, and the white brightness L of the anodized die-casting aluminum alloy is ≥85; the tensile strength of the anodized die-casting aluminum alloy is 180-210 MPa, the yield strength of the anodized die-casting aluminum alloy is 80-120 MPa, and the elongation of the anodized die-casting aluminum alloy is 3-5%.

[0007] Furthermore, the above-mentioned anodized die-casting aluminum alloy includes the following elements, in terms of mass percentage: 2-3% Mg element, 0.8-1.3% Si element, 1.6-2.4% Mn element, 0.2-0.3% Cu element, ≤1% Zn element and ≤0.15% Fe element, the total amount of unavoidable impurities is ≤0.1%, and the balance is Al element.

[0008] Furthermore, the sum of the contents of Mg and Zn elements is 2.3-3%.

[0009] Furthermore, the maximum size of the second phase in the anodized die-cast aluminum alloy is <30 μm, and / or the average size of the second phase in the anodized die-cast aluminum alloy is <15 μm; and / or the area proportion of the Fe-containing second phase in the anodized die-cast aluminum alloy is <2%.

[0010] According to another aspect of the present invention, a method for preparing the above-mentioned anodized die-casting aluminum alloy is provided, and the preparation method comprises: step S1, after raw materials including Al ingots, Zn ingots, Al-Mn master alloys, Al-Cu master alloys, Al-Si master alloys, and iron agents are sequentially batched and first smelted, Mg ingots are added for second smelting to obtain a first melt; step S2, raw materials including the first melt and the first refining agent are sequentially subjected to first stirring, first degassing and casting to obtain an ingot; step S3, the ingot is subjected to third smelting to obtain a second melt; step S4, raw materials including the second melt and the second refining agent are sequentially subjected to second stirring, second degassing and die-casting to obtain a die-casting aluminum alloy; and step S5, the die-casting aluminum alloy is subjected to anodizing treatment to obtain anodized die-casting aluminum alloy; wherein the anodizing treatment comprises chemical polishing, and the time of chemical polishing is 30 to 50 seconds.

[0011] Furthermore, in the above step S1, the temperature of the first smelting is 780-820°C; and / or the temperature of the second smelting is 740-760°C.

[0012] Furthermore, the above-mentioned step S2 also includes: performing a first standing and slagging in sequence after the first degassing; and / or, performing the first degassing in a nitrogen or argon atmosphere, and the first degassing time is 10 to 15 minutes; and / or, the first standing time is 15 to 20 minutes; and / or, the mass ratio of the first melt to the first refining agent is 1000:0.1 to 0.3; and / or, the first stirring time is 2 to 5 minutes, and / or, the casting temperature is 720 to 740°C, and / or, the casting mold temperature is 180 to 200°C.

[0013] Furthermore, the maximum size of the second phase in the ingot is <120 μm, and / or the area ratio of the Fe-containing second phase in the ingot is ≤2.5%, preferably ≤2%.

[0014] Furthermore, in the above step S3, the third smelting is to first increase the temperature to 770-800°C for insulation and then decrease the temperature to 750-760°C.

[0015] Furthermore, the above-mentioned step S4 also includes: performing a second standing and slagging in sequence after the second degassing; and / or, performing the second degassing in a nitrogen or argon atmosphere, and the second degassing time is 10 to 12 minutes; and / or, the second standing time is 15 to 20 minutes; and / or, the mass ratio of the second melt to the second refining agent is 1000:0.1 to 0.3; and / or, the second stirring time is 2 to 3 minutes, and / or, the die-casting temperature is 710 to 720°C, and / or, the die-casting mold temperature is 180 to 250°C.

[0016] By applying the technical solution of the present invention, the anodized die-casting aluminum alloy of the present application can ensure that the anodized die-casting aluminum alloy has good mechanical properties by adding Mg elements, but the substantial addition of Mg elements will significantly reduce the fluidity of the alloy, so controlling the content of Mg elements within the above range can ensure that the anodized die-casting aluminum alloy has good forming properties. The addition of Zn elements can effectively improve the mechanical properties of anodized die-casting aluminum alloys, but excessive addition of Zn elements will significantly reduce the fluidity of the alloy and aggravate the tendency of hot cracking, making it difficult to apply to high-quality 3C accessories. The present application can not only alleviate the reduction of alloy fluidity by controlling the total content of Mg elements and Zn elements within the above range, but also make the anodized die-casting aluminum alloy better applied to high-quality 3C accessories in combination with the above-mentioned other elements. Adding Si elements can not only greatly improve the fluidity of the melt and the forming properties of the anodized die-casting aluminum alloy, but also facilitate die-casting demolding, thereby significantly improving the yield of the anodized die-casting aluminum alloy, but when the content of Si elements increases to about 3%, the fluidity of the melt will also decrease, which is not conducive to the improvement of the forming properties of the anodized die-casting aluminum alloy. At the same time, since the less the content of Si element, the higher the white brightness of the surface of the anodized die-cast aluminum alloy, the present application controls the Si element to about 1%, so that the forming performance of the anodized die-cast aluminum alloy and the surface effect after anodization can be optimally balanced. Adding 0.2-0.3% of Cu element can make it completely dissolved into the matrix during the corresponding rapid cooling process, thereby improving the overall electrochemical activity of the anodized die-cast aluminum alloy. At the same time, during the anodizing stage, by coordinating the chemical polishing process with the Cu element content, the gloss and brightness of the anodized die-cast aluminum alloy can be further improved, so that the surface color difference of the anodized die-cast aluminum alloy is <0.3 and the white brightness L≥85. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0018] Figure 1 A scan of an anodized die-cast aluminum alloy in Example 1 of the present application is shown. DETAILED DESCRIPTION

[0019] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0020] As analyzed in the background technology of this application, in the prior art, there are problems such as it is difficult to achieve both excellent fluidity and surface gloss in anodized die-cast aluminum alloys, and the surface quality of anodized die-cast aluminum alloys is poor and the yield rate is low. In order to solve the above problems, this application provides an anodized die-cast aluminum alloy and a preparation method thereof.

[0021] In a typical embodiment of the present application, an anodized die-casting aluminum alloy is provided, which includes the following elements, in percentage by mass: 2-4% Mg element, 0.2-2% Si element, 1.6-2.4% Mn element, 0.2-0.3% Cu element, ≤2% Zn element and ≤0.2% Fe element, wherein the sum of the mass contents of Mg element and Zn element is 2-4%, the sum of the contents of unavoidable impurities is ≤0.2%, and the remainder is Al element; the surface color difference of the anodized die-casting aluminum alloy is <0.3, and the white brightness L of the anodized die-casting aluminum alloy is ≥85; the tensile strength of the anodized die-casting aluminum alloy is 180-210MPa, the yield strength of the anodized die-casting aluminum alloy is 80-120MPa, and the elongation of the anodized die-casting aluminum alloy is 3-5%.

[0022] The anodized die-casting aluminum alloy of the present application can ensure that the anodized die-casting aluminum alloy has good mechanical properties by adding Mg elements, but a large addition of Mg elements will significantly reduce the fluidity of the alloy. Therefore, controlling the content of Mg elements within the above range can ensure that the anodized die-casting aluminum alloy has good forming properties. The addition of Zn elements can effectively improve the mechanical properties of anodized die-casting aluminum alloys, but excessive addition of Zn elements will significantly reduce the fluidity of the alloy and aggravate the tendency of hot cracking, making it difficult to apply to high-quality 3C accessories. The present application can not only alleviate the reduction of alloy fluidity by controlling the total content of Mg elements and Zn elements within the above range, but also make the anodized die-casting aluminum alloy better applied to high-quality 3C accessories in combination with the above-mentioned other elements. Adding Si elements can not only greatly improve the fluidity of the melt and the forming properties of the anodized die-casting aluminum alloy, but also facilitate die-casting demolding, thereby significantly improving the yield of the anodized die-casting aluminum alloy, but when the content of Si elements increases to about 3%, the fluidity of the melt will also decrease, which is not conducive to the improvement of the forming properties of the anodized die-casting aluminum alloy. At the same time, since the less the content of Si element, the higher the white brightness of the surface of the anodized die-cast aluminum alloy, the present application controls the Si element to about 1%, so that the forming performance of the anodized die-cast aluminum alloy and the surface effect after anodization can be optimally balanced. Adding 0.2-0.3% of Cu element can make it completely dissolved into the matrix during the corresponding rapid cooling process, thereby improving the overall electrochemical activity of the anodized die-cast aluminum alloy. At the same time, during the anodizing stage, by coordinating the chemical polishing process with the Cu element content, the gloss and brightness of the anodized die-cast aluminum alloy can be further improved, so that the surface color difference of the anodized die-cast aluminum alloy is <0.3 and the white brightness L≥85.

[0023] In order to further improve the gloss, brightness and yield of the anodized die-cast aluminum alloy, in one embodiment of the present application, in order to further improve the synergistic effect between the elements, the anodized die-cast aluminum alloy preferably includes the following elements, in terms of mass percentage: 2-3% Mg element, 0.8-1.3% Si element, 1.6-2.4% Mn element, 0.2-0.3% Cu element, ≤1% Zn element and ≤0.15% Fe element, wherein the sum of the Mg element and the Zn element content is 2-3%, the total of unavoidable impurities is ≤0.1%, and the balance is Al element.

[0024] In order to further alleviate the reduction in alloy fluidity and enable the anodized die-cast aluminum alloy to be better applied to high-quality 3C accessories, in one embodiment of the present application, the sum of the content of Mg element and Zn element is 2.3-3%.

[0025] In one embodiment of the present application, the maximum size of the second phase in the anodized die-cast aluminum alloy is <30 μm, and / or the average size of the second phase in the anodized die-cast aluminum alloy is <15 μm; and / or the area proportion of the Fe-containing second phase in the anodized die-cast aluminum alloy is <2%.

[0026] It is preferred that the maximum size and average size of the second phase in the anodized die-cast aluminum alloy are within the above ranges, which helps to prevent the problem of stress concentration in the large-sized second phase as much as possible, thereby helping to improve the strength of the anodized die-cast aluminum alloy. It is preferred to control the area ratio of the Fe-containing second phase in the anodized die-cast aluminum alloy within the above range, which helps to reduce the deterioration effect of the Fe-containing second phase on the strength and anodizing performance of the anodized die-cast aluminum alloy, thereby helping to reduce the surface color difference of the anodized die-cast aluminum alloy and improve the yield rate of the anodized die-cast aluminum alloy.

[0027] In another typical embodiment of the present application, a method for preparing the above-mentioned anodized die-casting aluminum alloy is provided, and the preparation method comprises: step S1, wherein raw materials including Al ingots, Zn ingots, Al-Mn master alloys, Al-Cu master alloys, Al-Si master alloys, and iron agents are sequentially batched and first smelted, and then Mg ingots are added for second smelting to obtain a first melt; step S2, wherein the raw materials including the first melt and the first refining agent are sequentially subjected to first stirring, first degassing, and casting to obtain an ingot; step S3, wherein the ingot is subjected to a third smelting to obtain a second melt; step S4, wherein the raw materials including the second melt and the second refining agent are sequentially subjected to second stirring, second degassing, and die-casting to obtain a die-casting aluminum alloy; and step S5, wherein the die-casting aluminum alloy is subjected to anodizing treatment to obtain anodized die-casting aluminum alloy; wherein the anodizing treatment comprises chemical polishing, and the time of the chemical polishing is 30 to 50 seconds.

[0028] The present application can effectively improve the purity of the anodized die-casting aluminum alloy melt by refining and degassing in step S2 and step S4 respectively, thereby reducing the black spots and black spot defects that appear on the surface of the anodized die-casting aluminum alloy after anodizing. At the same time, controlling the time of chemical polishing within the above range can better match the content of Cu element in the raw material, thereby further improving the gloss and brightness of the anodized die-casting aluminum alloy. Specifically, step S1 can fully melt the above raw materials, so that the element components in the first melt are evenly distributed. Among them, adding Al-Si master alloy to the raw material instead of the traditional Si agent can improve the melting speed and uniformity of the Al-Si master alloy, thereby preventing the formation of a large-sized second phase and avoiding affecting the effective effect of the Si element. When preparing the ingot, a refining and a first degassing are performed by step S2, which can reduce impurities and gases in the melt, thereby improving the quality of the melt. The ingot is subjected to a third smelting, which can further refine the grains and improve the fluidity of the third melt, thereby facilitating subsequent die casting. The second refining and second degassing in step S4 can further purify the melt and reduce the gas content of the die-cast aluminum alloy, thereby increasing the density of the die-cast aluminum alloy and reducing the impurity phase exposed on the surface of the die-cast aluminum alloy, thereby significantly improving the yield of the anodized die-cast aluminum alloy. Finally, the die-cast aluminum alloy is anodized, especially by adjusting the content of the Cu element in the raw material and controlling the time of chemical polishing within the above range, which can significantly improve the gloss and brightness of the anodized die-cast aluminum alloy.

[0029] In one embodiment of the present application, in the above step S1, the temperature of the first smelting is 780-820°C; and / or the temperature of the second smelting is 740-760°C.

[0030] The temperature of the first smelting is preferably controlled within the above range, which helps to fully melt the above raw materials, thereby making the distribution of element components in the first melt more uniform. The temperature of the second smelting is preferably controlled within the above range, which helps to fully melt the Mg ingot and reduce the probability of burning of the Mg ingot as much as possible.

[0031] In one embodiment of the present application, the above-mentioned step S2 also includes: performing a first standing and slagging in sequence after the first degassing; and / or, performing the first degassing in a nitrogen or argon atmosphere, and the first degassing time is 10 to 15 minutes; and / or, the first standing time is 15 to 20 minutes; and / or, the mass ratio of the first melt and the first refining agent is 1000:0.1 to 0.3; and / or, the first stirring time is 2 to 5 minutes, and / or, the casting temperature is 720 to 740°C, and / or, the casting mold temperature is 180 to 200°C.

[0032] It is preferred to control the mass ratio of the first melt and the first refining agent and the first stirring time within the above range, and the first refining agent is preferably a chloride salt, more preferably zinc chloride, manganese chloride and ferric chloride, which is helpful for the first melt and the first refining agent to be fully mixed, thereby helping to purify the melt. It is preferred to carry out the first degassing in a nitrogen or argon atmosphere, and control the first degassing time within the above range, which is helpful to further reduce impurities and gases in the melt, thereby helping to further improve the quality of the melt. It is preferred to carry out the first standing and slagging in sequence after the first degassing, and control the first standing time within the above range, which is helpful to fully release the gas in the melt, and to facilitate the removal of impurities in the melt by slagging.

[0033] In one embodiment of the present application, the maximum size of the second phase in the ingot is <120 μm, and / or the area ratio of the Fe-containing second phase in the ingot is ≤2.5%, preferably ≤2%.

[0034] Preferably, the maximum size of the second phase in the ingot is within the above range, which helps to improve the grain texture, thereby helping to improve the strength of the ingot. Preferably, the area ratio of the Fe-containing second phase in the ingot is controlled within the above range, which helps to slow down the deterioration of the strength and anodizing performance of the ingot by the Fe-containing second phase, thereby helping to reduce the surface color difference of the anodized die-cast aluminum alloy, and further improve the yield of the anodized die-cast aluminum alloy.

[0035] In order to fully melt the ingot, in one embodiment of the present application, in the above step S3, the third smelting is to first heat the temperature to 770-800°C, keep the temperature, and then cool it down to 750-760°C.

[0036] In one embodiment of the present application, the above-mentioned step S4 also includes: performing a second standing and slagging in sequence after the second degassing; and / or, performing the second degassing in a nitrogen or argon atmosphere, and the second degassing time is 10 to 12 minutes; and / or, the second standing time is 15 to 20 minutes; and / or, the mass ratio of the second melt and the second refining agent is 1000:0.1 to 0.3; and / or, the second stirring time is 2 to 3 minutes, and / or, the die-casting temperature is 710 to 720°C, and / or, the die-casting mold temperature is 180 to 250°C.

[0037] It is preferred to control the mass ratio of the second melt and the second refining agent and the time of the second stirring within the above range, and the type of the second refining agent is preferably chloride salt, and more preferably zinc chloride, manganese chloride and ferric chloride, which helps to promote the second melt and the second refining agent to be fully mixed, and at the same time prevent the second refining agent from remaining in the melt too much as possible, resulting in the appearance of impurities containing refining agent components such as Fe and Ca. In addition, too little second refining agent will lead to incomplete purification of the melt. Therefore, controlling the mass of the second melt and the second refining agent within the above range helps to thoroughly purify the melt. It is preferred to carry out the second degassing in an atmosphere of nitrogen or argon, and control the time of the second degassing within the above range, which helps to further reduce impurities and gases in the melt, thereby helping to further improve the quality of the melt. It is preferred that the second standing and slagging are carried out in sequence after the second degassing, and the time of the second standing is controlled within the above range, which helps to fully release the gas in the melt, and slagging is conducive to removing impurities in the melt, thereby helping to further improve the density of the die-cast aluminum alloy, and then help to improve the yield of the anodized die-cast aluminum alloy.

[0038] The beneficial effects of the present application will be further illustrated below in conjunction with embodiments.

[0039] Example 1

[0040] In terms of mass percentage, the anodized die-casting aluminum alloy raw material is smelted according to the composition ratio of 2% Mg element, 0.2% Si element, 1.6% Mn element, 0.2% Cu element, 0.1% Zn element, 0.2% Fe element, and the balance Al element. Specifically, the raw materials including Al ingot, Zn ingot, Al-Mn master alloy, Al-Cu master alloy, Al-Si master alloy, and iron agent are batched and smelted in sequence, and then Mg ingot is added for second smelting to obtain a first melt, wherein the temperature of the first smelting is 780°C and the temperature of the second smelting is 740°C.

[0041] The raw materials including 300 kg of the first melt and 30 g of the first refining agent ferric chloride are sequentially subjected to first stirring for 2 minutes, first degassing for 10 minutes in a nitrogen atmosphere, first standing for 15 minutes, slagging and casting to obtain an ingot, wherein the casting temperature is 720°C and the casting mold temperature is 180°C.

[0042] The ingot is put into a melting furnace of a die-casting machine for a third melting to obtain a second melt. Specifically, the temperature is first raised to 770° C. and kept warm until the ingot is completely melted, and then the temperature is lowered to 750° C. and kept warm.

[0043] The raw materials including 300 kg of the second melt and 60 g of the second refining agent ferric chloride were sequentially subjected to second stirring for 2 minutes, second degassing for 10 minutes in a nitrogen atmosphere, second standing for 15 minutes, slagging and die casting to obtain a die-casting aluminum alloy, wherein the die-casting temperature was 710°C and the die casting mold temperature was 180°C.

[0044] The die-cast aluminum alloy is anodized to obtain an anodized die-cast aluminum alloy, wherein the anodizing treatment includes alkali washing, neutralization, chemical polishing, anodizing, dyeing and sealing in sequence, wherein the chemical polishing time is 50s.

[0045] Example 2

[0046] The anodized die-casting aluminum alloy raw material is smelted according to the composition ratio of 3% Mg element, 1% Si element, 2% Mn element, 0.3% Cu element, 1% Zn element, 0.15% Fe element, and the balance Al element in terms of mass percentage. Specifically, the raw materials including Al ingot, Zn ingot, Al-Mn master alloy, Al-Cu master alloy, Al-Si master alloy, and iron agent are batched and smelted in sequence, and then Mg ingot is added for second smelting to obtain a first melt, wherein the temperature of the first smelting is 800°C and the temperature of the second smelting is 750°C.

[0047] The raw materials including 300 kg of the first melt and 60 g of the first refining agent ferric chloride are sequentially subjected to first stirring for 4 minutes, first degassing for 12 minutes in a nitrogen atmosphere, first standing for 18 minutes, slagging and casting to obtain an ingot, wherein the casting temperature is 730°C and the casting mold temperature is 190°C.

[0048] The ingot is put into a melting furnace of a die-casting machine for a third melting to obtain a second melt. Specifically, the temperature is first raised to 790° C. and kept warm until the ingot is completely melted, and then the temperature is lowered to 755° C. and kept warm.

[0049] The raw materials including 300 kg of the second melt and 30 g of the second refining agent ferric chloride were sequentially subjected to second stirring for 2.5 min, second degassing for 11 min in a nitrogen atmosphere, second standing for 18 min, slagging and die casting to obtain a die-cast aluminum alloy, wherein the die-casting temperature was 715° C. and the die-casting mold temperature was 215° C.

[0050] The die-cast aluminum alloy is anodized to obtain an anodized die-cast aluminum alloy, wherein the anodizing treatment includes alkali washing, neutralization, chemical polishing, anodizing, dyeing and sealing in sequence, wherein the chemical polishing time is 40s.

[0051] Example 3

[0052] The anodized die-casting aluminum alloy raw material is smelted according to the composition ratio of 4% Mg element, 2% Si element, 2.4% Mn element, 0.3% Cu element, 0.1% Fe element, and the balance Al element in terms of mass percentage. Specifically, the raw materials including Al ingot, Al-Mn master alloy, Al-Cu master alloy, Al-Si master alloy, and iron agent are batched and smelted in sequence, and then Mg ingot is added for second smelting to obtain a first melt, wherein the temperature of the first smelting is 820° C. and the temperature of the second smelting is 760° C.

[0053] The raw materials including 300 kg of the first melt and 90 g of the first refining agent ferric chloride are sequentially subjected to first stirring for 5 minutes, first degassing for 15 minutes in a nitrogen atmosphere, first standing for 20 minutes, slagging and casting to obtain an ingot, wherein the casting temperature is 740°C and the casting mold temperature is 200°C.

[0054] The ingot is put into a melting furnace of a die-casting machine for a third melting to obtain a second melt. Specifically, the temperature is first raised to 800° C. and kept warm until the ingot is completely melted, and then the temperature is lowered to 760° C. and kept warm.

[0055] The raw materials including 300 kg of the second melt and 60 g of the second refining agent ferric chloride were sequentially subjected to second stirring for 3 minutes, second degassing for 12 minutes in a nitrogen atmosphere, second standing for 20 minutes, slagging and die casting to obtain a die-casting aluminum alloy, wherein the die-casting temperature is 720°C and the die casting mold temperature is 250°C.

[0056] The die-cast aluminum alloy is anodized to obtain an anodized die-cast aluminum alloy, wherein the anodizing treatment includes alkali washing, neutralization, chemical polishing, anodizing, dyeing and sealing in sequence, wherein the chemical polishing time is 30s.

[0057] Example 4

[0058] The difference from Example 1 is that the mass content of the Mg element is 1.3%, the mass content of the Zn element is 1%, and the total mass of the Mg element and the Zn element is 2%, and finally an anodized die-casting aluminum alloy is obtained.

[0059] Example 5

[0060] The difference from Example 1 is that the mass content of the Mg element is 2%, the mass content of the Zn element is 1%, and the total mass of the Mg element and the Zn element is 3%, and finally an anodized die-casting aluminum alloy is obtained.

[0061] Example 6

[0062] The difference from Example 1 is that the mass content of Mg element is 1%, the mass content of Zn element is 2.5%, and the total mass of Mg element and Zn element is 3.5%, and finally an anodized die-casting aluminum alloy is obtained.

[0063] Example 7

[0064] The difference from Example 1 is that the raw materials including 300 kg of the first melt and 30 g of the first refining agent ferric chloride are sequentially subjected to a first stirring for 5 minutes, a first degassing for 15 minutes in a nitrogen atmosphere, a first standing for 20 minutes, slagging and casting to obtain an ingot, wherein the casting temperature is 740° C., the casting mold temperature is 200° C., and finally an anodized die-casting aluminum alloy is obtained.

[0065] Example 8

[0066] The difference from Example 1 is that the raw materials including 300 kg of the first melt and 30 g of the first refining agent ferric chloride are sequentially subjected to a first stirring for 7 minutes, a first degassing for 20 minutes in a nitrogen atmosphere, a first standing for 25 minutes, slagging and casting to obtain an ingot, wherein the casting temperature is 700° C., the casting mold temperature is 250° C., and finally an anodized die-casting aluminum alloy is obtained.

[0067] Example 9

[0068] The difference from Example 1 is that the raw materials including 300 kg of the second melt and 30 g of the second refining agent ferric chloride are sequentially subjected to a second stirring for 3 minutes, a second degassing for 12 minutes in a nitrogen atmosphere, a second standing for 20 minutes, slag removal and die casting to obtain a die-cast aluminum alloy, wherein the die-casting temperature is 720°C, the die-casting mold temperature is 250°C, and finally an anodized die-cast aluminum alloy is obtained.

[0069] Example 10

[0070] The difference from Example 1 is that the raw materials including 300 kg of the second melt and 30 g of the second refining agent ferric chloride are sequentially subjected to a second stirring for 5 minutes, a second degassing for 15 minutes in a nitrogen atmosphere, a second standing for 30 minutes, slag removal and die casting to obtain a die-cast aluminum alloy, wherein the die-casting temperature is 750°C, the die-casting mold temperature is 280°C, and finally an anodized die-cast aluminum alloy is obtained.

[0071] Embodiment 11

[0072] The difference from Example 1 is that the die-cast aluminum alloy is anodized to obtain an anodized die-cast aluminum alloy, wherein the anodizing treatment includes alkaline washing, neutralization, chemical polishing, anodizing, dyeing and sealing performed in sequence, and the chemical polishing time is 30s.

[0073] Comparative Example 1

[0074] The difference from Example 1 is that, in terms of mass percentage, the anodized die-casting aluminum alloy raw material is smelted according to the composition ratio of 4% Mg element, 0.2% Si element, 1.6% Mn element, 0.2% Cu element, 3% Zn element, 0.2% Fe element, and the balance Al element. Specifically, the raw materials including Al ingots, Zn ingots, Al-Mn master alloys, and Al-Cu master alloys are sequentially batched and smelted for the first time, and then Mg ingots are added for the second smelting to obtain a first melt, and finally the anodized die-casting aluminum alloy is obtained.

[0075] Comparative Example 2

[0076] The difference from Example 1 is that, in terms of mass percentage, the anodized die-casting aluminum alloy raw material is smelted according to the composition ratio of 2% Mg element, 3% Si element, 1.6% Mn element, 0.5% Cu element, 0.1% Zn element, 0.2% Fe element, and the balance Al element. Specifically, the raw materials including Al ingots, Zn ingots, Al-Mn master alloys, and Al-Cu master alloys are sequentially batched and smelted for the first time, and then Mg ingots are added for the second smelting to obtain a first melt, and finally the anodized die-casting aluminum alloy is obtained.

[0077] Comparative Example 3

[0078] The difference from Example 1 is that the die-cast aluminum alloy is anodized to obtain an anodized die-cast aluminum alloy, wherein the anodizing treatment includes alkaline washing, neutralization, chemical polishing, anodizing, dyeing and sealing performed in sequence, and the chemical polishing time is 60s.

[0079] Comparative Example 4

[0080] The difference from Example 1 is that the die-cast aluminum alloy is anodized to obtain an anodized die-cast aluminum alloy, wherein the anodizing treatment includes alkaline washing, neutralization, chemical polishing, anodizing, dyeing and sealing performed in sequence, and the chemical polishing time is 20s.

[0081] Comparative Example 5

[0082] The difference from Example 1 is that the second melt is directly die-cast to obtain a die-cast aluminum alloy, and finally an anodized die-cast aluminum alloy is obtained.

[0083] Comparative Example 6

[0084] The difference from Example 1 is that the first melt is directly cast to obtain an ingot, and finally an anodized die-cast aluminum alloy is obtained.

[0085] Test Method

[0086] Maximum size and average size test of the second phase: Tested in accordance with GB / T 15749-2008.

[0087] Test on the area ratio of the Fe-containing second phase: the test is carried out in accordance with GB / T 15749-2008.

[0088] Tensile strength, yield strength and elongation: tested in accordance with GBT 228.1-2021.

[0089] Surface color difference test: Use a colorimeter to test the surface color difference, take the L, a, b values ​​of more than 10 consecutive test points, and calculate the color difference △E=(△L 2 +△a 2 +△b 2 ) ^2 .

[0090] White brightness L test: Use a colorimeter to test and take the average of the L values ​​of more than 10 consecutive points.

[0091] The ingots and anodized die-cast aluminum alloys of the above embodiments and comparative examples were subjected to performance tests. The test results are shown in Tables 1 and 2.

[0092] Table 1

[0093]

[0094] Table 2

[0095]

[0096] in, Figure 1 is a scan of the anodized die-cast aluminum alloy in Example 1, Figure 1 It can be seen that the second phase in the anodized die-cast aluminum alloy is evenly distributed and small in size. Compared with Example 4 and Example 5, the formability of the anodized die-cast aluminum alloy of Example 6 is poor. The formability of Comparative Example 1 is poor. The maximum size of the second phase of the anodized die-cast aluminum alloy of Comparative Example 2 increases, and the color difference and white brightness are significantly reduced. The white brightness of the anodized die-cast aluminum alloys of Comparative Examples 3 and 4 decreases. The maximum size of the second phase of the anodized die-cast aluminum alloys of Comparative Examples 5 and 6 increases, and the area proportion of the Fe-containing second phase increases, so a color difference problem occurs.

[0097] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0098] The anodized die-casting aluminum alloy of the present application can ensure that the anodized die-casting aluminum alloy has good mechanical properties by adding Mg elements, but a large addition of Mg elements will significantly reduce the fluidity of the alloy. Therefore, controlling the content of Mg elements within the above range can ensure that the anodized die-casting aluminum alloy has good forming properties. The addition of Zn elements can effectively improve the mechanical properties of anodized die-casting aluminum alloys, but excessive addition of Zn elements will significantly reduce the fluidity of the alloy and aggravate the tendency of hot cracking, making it difficult to apply to high-quality 3C accessories. The present application can not only alleviate the reduction of alloy fluidity by controlling the total content of Mg elements and Zn elements within the above range, but also make the anodized die-casting aluminum alloy better applied to high-quality 3C accessories in combination with the above-mentioned other elements. Adding Si elements can not only greatly improve the fluidity of the melt and the forming properties of the anodized die-casting aluminum alloy, but also facilitate die-casting demolding, thereby significantly improving the yield of the anodized die-casting aluminum alloy, but when the content of Si elements increases to about 3%, the fluidity of the melt will also decrease, which is not conducive to the improvement of the forming properties of the anodized die-casting aluminum alloy. At the same time, since the less the content of Si element, the higher the white brightness of the surface of the anodized die-cast aluminum alloy, the present application controls the Si element to about 1%, so that the forming performance of the anodized die-cast aluminum alloy and the surface effect after anodization can be optimally balanced. Adding 0.2-0.3% of Cu element can make it completely dissolved into the matrix during the corresponding rapid cooling process, thereby improving the overall electrochemical activity of the anodized die-cast aluminum alloy. At the same time, during the anodizing stage, by coordinating the chemical polishing process with the Cu element content, the gloss and brightness of the anodized die-cast aluminum alloy can be further improved, so that the surface color difference of the anodized die-cast aluminum alloy is <0.3 and the white brightness L≥85.

[0099] The above are only embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An anodized die-cast aluminum alloy, characterized in that: The anodized die-casting aluminum alloy includes the following elements in percentage by mass: 2-4% Mg, 0.2-2% Si, 1.6-2.4% Mn, 0.2-0.3% Cu, ≤2% Zn, ≤0.2% Fe, the total content of unavoidable impurities is ≤0.2%, and the balance is Al; wherein the sum of the mass contents of the Mg and Zn elements is 2-4%; The surface color difference of the anodized die-cast aluminum alloy is less than 0.3, and the white brightness L of the anodized die-cast aluminum alloy is greater than or equal to 85; the tensile strength of the anodized die-cast aluminum alloy is 180 to 210 MPa, the yield strength of the anodized die-cast aluminum alloy is 80 to 120 MPa, and the elongation of the anodized die-cast aluminum alloy is 3 to 5%.

2. The anodized die-cast aluminum alloy according to claim 1, characterized in that: The anodized die-casting aluminum alloy includes the following elements in percentage by mass: 2-3% of the Mg element, 0.8-1.3% of the Si element, 1.6-2.4% of the Mn element, 0.2-0.3% of the Cu element, ≤1% of the Zn element, ≤0.15% of the Fe element, the total of unavoidable impurities ≤0.1%, and the balance being the Al element.

3. The anodized die-cast aluminum alloy according to claim 1 or 2, characterized in that: The sum of the content of the Mg element and the Zn element is 2.3-3%.

4. The anodized die-cast aluminum alloy according to any one of claims 1 to 3, characterized in that: The maximum size of the second phase in the anodized die-cast aluminum alloy is <30 μm, and / or the average size of the second phase in the anodized die-cast aluminum alloy is <15 μm; and / or the area proportion of the Fe-containing second phase in the anodized die-cast aluminum alloy is <2%.

5. A method for preparing the anodized die-cast aluminum alloy according to any one of claims 1 to 4, characterized in that: The preparation method comprises: Step S1, after sequentially batching and first smelting raw materials including Al ingot, Zn ingot, Al-Mn master alloy, Al-Cu master alloy, Al-Si master alloy and iron agent, adding Mg ingot for second smelting to obtain a first melt; Step S2, subjecting the raw materials including the first melt and the first refining agent to first stirring, first degassing and casting in sequence to obtain an ingot; Step S3, performing a third smelting on the ingot to obtain a second melt; Step S4, sequentially performing second stirring, second degassing and die casting on the raw material including the second melt and the second refining agent to obtain a die-cast aluminum alloy; and Step S5, subjecting the die-cast aluminum alloy to anodizing treatment to obtain the anodized die-cast aluminum alloy; Wherein, the anodizing treatment includes chemical polishing, and the time of the chemical polishing is 30 to 50 seconds.

6. The preparation method according to claim 5, characterized in that: In the step S1, the temperature of the first smelting is 780-820°C; and / or the temperature of the second smelting is 740-760°C.

7. The preparation method according to claim 5 or 6, characterized in that: The step S2 further comprises: performing first standing and slagging in sequence after the first degassing; and / or performing the first degassing in a nitrogen or argon atmosphere, the first degassing time being 10 to 15 minutes; and / or the first standing time being 15 to 20 minutes; And / or, the mass ratio of the first melt to the first refining agent is 1000:0.1-0.3; and / or, the first stirring time is 2-5 min, and / or, the casting temperature is 720-740°C, and / or, the casting mold temperature is 180-200°C.

8. The preparation method according to any one of claims 5 to 7, characterized in that: The maximum size of the second phase in the ingot is <120 μm, and / or the area ratio of the Fe-containing second phase in the ingot is ≤2.5%, preferably ≤2%.

9. The preparation method according to any one of claims 5 to 8, characterized in that: In the step S3, the third smelting is to first increase the temperature to 770-800°C, keep the temperature, and then decrease the temperature to 750-760°C.

10. The preparation method according to any one of claims 5 to 9, characterized in that: The step S4 further comprises: performing a second standing and slagging in sequence after the second degassing; and / or performing the second degassing in a nitrogen or argon atmosphere, the second degassing time being 10 to 12 minutes; and / or the second standing time being 15 to 20 minutes; And / or, the mass ratio of the second melt to the second refining agent is 1000:0.1-0.3; and / or, the second stirring time is 2-3 min, and / or, the die-casting temperature is 710-720°C, and / or, the die-casting mold temperature is 180-250°C.

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