7-series aluminum alloy and preparation method and application thereof

Abstract

The invention discloses a 7-series aluminum alloy and a preparation method and application thereof. The 7-series aluminum alloy comprises the following components in percentage by mass: 7.00% to 10.00% of Zn, 2.00% to 4.00% of Mg, 0.20% to 0.60% of Cu, 0.05% to 0.18% of Mn, 0.04% to 0.20% of Er, Tilt, and the balance of Al and inevitable impurities. The aluminum alloy comprises, by weight, 0.05% of Al, 0.05% of Al, 0.10% or less of Fe, 0.10% or less of Si and the balance Al Through reasonable matching of all the components of Zn, Mg, Cu, Mn, Er, Ti, Fe, Si and Al, the 7-series aluminum alloy has excellent high strength and a good anodic oxidation effect, and the application requirements of 3C products for high strength and high appearance quality of aluminum alloy materials can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and in particular to a 7-series aluminum alloy and its preparation method and application. Background Art

[0002] The strength of heat-treatable aluminum alloys can be improved after solution treatment, quenching and aging, and they can be widely used in a series of 3C products such as computers, communications and consumer electronics. For example, aluminum alloy smartphones, laptops, iPads, etc., are light in weight, beautiful in appearance and excellent in texture, and are deeply loved by consumers. With the development of 3C products towards lighter and smaller sizes, higher requirements are put forward for the strength of aluminum alloy materials. The strength of the currently widely used 6-series (Al-Mg-Si) aluminum alloy has approached its limit and it is difficult to meet the continuous development needs of 3C products.

[0003] After aging, the 7-series (Al-Zn-Mg) aluminum alloy can precipitate high-density nanoscale η′ (MgZn2) strengthening phases, and the yield strength can be increased to more than 500 MPa, showing good prospects for use in 3C products. However, in addition to strength, good anodic oxidation effect is a key indicator. Some existing 7-series aluminum alloy products have high strength and are widely used in the fields of aerospace and the like. The applications in aerospace require structural materials to have high mechanical and corrosion resistance properties. Therefore, relatively high amounts of copper elements (1.5 - 2.5%, by weight percentage) and microalloying elements such as zirconium and chromium are added to these alloys to obtain a fibrous partially recrystallized structure and obtain Mg(Zn,Cu)2 phases. However, such microstructural characteristics lead to poor anodic oxidation effect and cannot meet the actual requirements. Therefore, for applications in the 3C field, the contents of copper and microalloying elements need to be reduced, but in order to ensure high strength, the alloying degree of zinc and magnesium must be increased, which brings many problems, such as an increase in coarse secondary phases in the alloy, large size and difficulty in elimination; the extrusion forming of the material is difficult, and the grain structure is extremely easy to coarsen during the heat treatment process, resulting in the final strength and anodic oxidation effect being difficult to meet the requirements. This seriously hinders the application of this series of alloys in 3C products.

[0004] Therefore, developing a new 7-series aluminum alloy with high strength and good oxidation effect is of great significance for promoting the development of aluminum processing and the 3C field. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. For this reason, in the first aspect of the present invention, a 7-series aluminum alloy is proposed, and this 7-series aluminum alloy has the characteristics of high strength and good surface treatment effect.

[0006] In the second aspect of the present invention, a preparation method of a 7-series aluminum alloy is also provided.

[0007] In the third aspect of the present invention, an application of a 7-series aluminum alloy is also provided.

[0008] A 7-series aluminum alloy provided by an embodiment of the first aspect of the present invention includes the following components calculated by mass percentage:

[0009] Zn: 7.00% - 10.00%, Mg: 2.00% - 4.00%, Cu: 0.20% - 0.60%, Mn: 0.05% - 0.18%, Er: 0.04% - 0.20%, Ti < 0.05%, Fe ≤ 0.10%, Si ≤ 0.10%, and the balance is Al and unavoidable impurities.

[0010] The 7-series aluminum alloy provided by the embodiment of the present invention has at least the following beneficial effects:

[0011] Through the reasonable combination of each component of Zn, Mg, Cu, Mn, Er, Ti, Fe, Si, and Al in the present invention, the 7-series aluminum alloy has excellent high strength and good anodic oxidation effect, and can meet the application requirements of 3C products for high strength and high appearance quality of aluminum alloy materials.

[0012]

[0013] Furthermore, the addition of a certain amount of Cu element can promote the high-density precipitation of precipitation strengthening phases in the 7-series aluminum alloy, reduce the potential difference between the grain boundary precipitation phase and the intragranular phase in the material, and is beneficial to obtaining high strength and good anodic oxidation effect. When the addition amount of Cu element increases, the strengthening effect is improved to some extent, but it will lead to the appearance of complex and coarse secondary phases, such as Al7Cu2Fe and Al2CuMg primary phases. These secondary phases have high melting points and large sizes, and are often difficult to eliminate during subsequent deformation and heat treatment, resulting in difficulty in ensuring the final anodic oxidation effect. In addition, the density of Cu element is high, and too much addition will increase the density of the alloy, which is not conducive to the lightweight of 3C products. Therefore, on the basis of determining the content of Zn and Mg elements, further optimizing the addition amount of Cu element also provides a composition guarantee for obtaining high strength and good anodic oxidation effect.

[0014] ​Furthermore, Fe and Si are common impurity elements in 7xxx series aluminum alloys, often forming hard and brittle phases such as AlFeSi, AlFeMnSi, and Al7Cu2Fe, which reduce the processing performance of the material, deteriorate the surface quality of the material, and the final anodizing effect. Therefore, the contents of Fe and Si elements should be minimized as much as possible. Based on the research of the present invention, the Fe and Si in the present invention are controlled within the above ranges of Fe≤0.10% and Si≤0.10%, which can preferably avoid the occurrence of the above problems. Although further reducing their contents can still have an effect, it will bring a substantial increase in cost. Therefore, considering comprehensively, the contents of Fe and Si elements in the present invention are controlled to be ≤0.10%.

[0015] According to a preferred embodiment of the present invention, the 7xxx series aluminum alloy comprises the following components calculated by mass percentage: Zn: 8.50% - 9.50%, Mg: 2.80% - 3.80%, Cu: 0.30% - 0.50%, Mn: 0.08% - 0.14%, Er: 0.05% - 0.10%, Ti < 0.05%, Fe≤0.10%, Si≤0.10%, and the balance is Al and inevitable impurities.

[0016] According to a preferred embodiment of the present invention, in the 7xxx series aluminum alloy, 0.10% < Mn + Er < 0.18%.

[0017] The microalloying elements Mn and Er can refine the as-cast grains of the 7xxx series aluminum alloy, which is beneficial to the improvement of extrusion performance. In addition, they can play a role in inhibiting recrystallization in the 7xxx series aluminum alloy. For 3C products, good anodizing requires recrystallized grains of a certain size and uniformity. During hot plastic deformation and heat treatment, recrystallization in the material is likely to occur, and the grains grow. Therefore, appropriate contents of Mn and Er elements are crucial to form the best size and quantity of dispersed phases, which can not only make the material matrix recrystallize but also control its growth rate to obtain relatively ideal recrystallized grains. If the contents of these two elements are too low, sufficient dispersed phases cannot be formed, and the recrystallized grains of the material are coarse and uneven; if the element contents are too high, coarse AlFeMnSi phases and Er-containing phases will be formed, reducing the plasticity of the material and remaining in the final product, deteriorating the anodizing effect. Therefore, the present invention designs 0.10% < Mn + Er < 0.18%, which can effectively solve the above problems and provide guarantee for the good extrusion processing performance and anodizing effect of the material.

[0018] According to a preferred embodiment of the present invention, among the inevitable impurities of the present invention, other single impurities ≤0.02%, and the total impurities ≤0.10%.

[0019] According to the second aspect embodiment of the present invention, a preparation method of a 7xxx series aluminum alloy is provided; it comprises the following steps:

[0020] S1. Mix Zn, Mg, Cu, Mn, Er, Ti, Fe, Si and Al and carry out melting and casting to obtain a billet;

[0021] S2. Carry out homogenization treatment on the billet to obtain an ingot blank;

[0022] S3. Preheat and extrude the ingot blank to obtain an extruded material;

[0023] S4. Carry out aging treatment on the extruded material to obtain the product.

[0024] According to a preferred embodiment of the present invention, in step S1, the temperature of the melting is 720 - 800 °C.

[0025] According to a preferred embodiment of the present invention, in step S1, the temperature of the casting is 680 - 740 °C.

[0026] According to a preferred embodiment of the present invention, in step S1, the cooling water flow rate of the casting is 5 - 10 m 3 / min.

[0027] According to a preferred embodiment of the present invention, in step S1, after melting, online degassing and slag removal are also required.

[0028] According to a preferred embodiment of the present invention, in step S1, the average grain size of the core of the billet ≤ 250 μm, and the maximum grain size ≤ 550 μm.

[0029] According to a preferred embodiment of the present invention, in step S2, the steps of the homogenization treatment include:

[0030] Keep warm at a temperature of 300 - 360 °C for 3 - 5 h; keep warm at a temperature of 420 - 470 °C for 4 - 6 h; keep warm at a temperature of 490 - 550 °C for 12 - 25 h.

[0031] According to a preferred embodiment of the present invention, in step S2, after the homogenization treatment, a cooling step is also included. Air cooling and spray cooling are used to cool to room temperature, and the cooling rate is 100 - 200 °C / h.

[0032] According to a preferred embodiment of the present invention, in step S2, the proportion of the Mn and Er dispersion phases with a size of 10 nm - 25 nm in the ingot blank ≥ 80 wt.%.

[0033] According to a preferred embodiment of the present invention, in step S3, the conditions of the extrusion include:

[0034] Heating temperature 400 °C - 480 °C; die temperature 420 °C - 460 °C.

[0035] According to a preferred embodiment of the present invention, in step S3, the conditions for extrusion include:

[0036] Heating temperature: 460°C to 480°C; die temperature: 440°C to 460°C.

[0037] According to a preferred embodiment of the present invention, in step S3, the extrusion speed is 2 to 6 m / min. Preferably, the extrusion speed is 3 to 5 m / min.

[0038] According to a preferred embodiment of the present invention, in step S3, the extrusion outlet temperature is 460°C to 540°C. Further preferably, the extrusion outlet temperature is 480°C to 520°C.

[0039] According to a preferred embodiment of the present invention, in step S3, the extrusion material is quenched online and cooled to room temperature, and the quenching and cooling rate in the temperature range above 200°C is ≥30°C / s.

[0040] According to a preferred embodiment of the present invention, in step S3, the extrusion material is cooled to complete recrystallization, with equiaxed grains, an average grain intercept <150 μm, and a maximum grain intercept <300 μm.

[0041] According to a preferred embodiment of the present invention, in step S4, the steps of the aging treatment include:

[0042] Insulate at a temperature of 60 to 120°C for 2 to 20 h; then insulate at a temperature of 130 to 170°C for 2 to 16 h.

[0043] According to a preferred embodiment of the present invention, in step S4, the steps of the aging treatment include:

[0044] Insulate at a temperature of 80 to 110°C for 3 to 12 h; then insulate at a temperature of 140 to 160°C for 2 to 12 h.

[0045] The third aspect of the present invention provides an application of the 7-series aluminum alloy described in the first aspect of the present invention in the preparation of 3C products.

[0046] According to a preferred embodiment of the present invention, the 3C products include computers, tablets, mobile phones, smart watches, cameras, and televisions.

[0047] Other features and advantages of the present invention will be described in the subsequent description, and some of them will become obvious from the description or be understood by implementing the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the following description of embodiments in conjunction with the accompanying drawings, wherein:

[0049] Figure 1 is the metallographic structure diagram of 7xxx series aluminum alloy of the embodiment and comparative example of the present invention;

[0050] Figure 2 is the anodic oxidation effect diagram of 7xxx series aluminum alloy of the embodiment and comparative example of the present invention.

[0051] Figure 3 is the proportion diagram of Mn and Er dispersed phases with a size of 10 nm - 25 nm in the ingot blank of Embodiment 1 of the present invention. Detailed Embodiments

[0052] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the embodiments. However, the present invention is not limited to these embodiments.

[0053] The reagents, methods, and equipment used in the present invention are all conventional reagents, methods, and equipment in the technical field, unless otherwise specified.

[0054] Some raw materials in the embodiments of the present invention are as follows:

[0055] Aluminum ingots (commercially available), magnesium ingots (commercially available), zinc ingots (commercially available), Al-20%Cu master alloy (commercially available), Al-4%Mn master alloy (commercially available), Al-10%Er master alloy (commercially available), Al-5%Ti-B master alloy (commercially available).

[0056] Embodiment 1

[0057] This example provides a 7xxx series aluminum alloy, and the contents of its various components are shown in Table 1. Its preparation method is as follows:

[0058] S1. Weigh the raw materials according to the above element percentages. The raw materials used are aluminum ingots, magnesium ingots, zinc ingots, Al-20%Cu master alloy, Al-4%Mn master alloy, Al-10%Er master alloy, and Al-5%Ti-B master alloy. First, melt the aluminum ingots, magnesium ingots, and zinc ingots at 760 °C, and then add the Al-Cu master alloy, Al-Mn master alloy, Al-Er master alloy, and Al-Ti-B master alloy. After complete melting, refine the melt at 740 °C, and then let it stand for 30 min at 730 °C. After standing, conduct online degassing and slag removal. The degassing is carried out using a double graphite rotor online degassing device, and the degassing medium is high-purity argon. After degassing, the hydrogen content in the molten aluminum is ≤0.15 mL / 100Al. The slag removal uses a two-stage slag removal system. The first stage is a ceramic filter plate slag removal device, and the second stage is a tubular filter. Then, use the semi-continuous casting method for casting. The casting temperature is 720 °C, and the casting cooling water flow rate is 6 m3 / min to obtain a billet with a diameter of Φ226mm.

[0059] S2. The billet is subjected to homogenization heat treatment using a three-stage homogenization process of 330°C / 4h + 440°C / 5h + 495°C / 20h, and then cooled by strong wind and spraying to obtain an average cooling rate of about 160°C / h. Then it is cut into ingots with a length of 600mm.

[0060] S3. The ingot is preheated in a gas furnace at 470°C, and the preheating temperature of the mold is 460°C. Then it is extruded, with an extrusion speed of 3.5m / min and an extrusion ratio of 35; after hot extrusion, it is quenched online with water.

[0061] S4. Subsequently, the extruded material is transferred to an aging furnace for two-stage aging treatment of 90°C / 10h + 150°C / 6h.

[0062] The proportion diagram of the Mn and Er dispersion phases with a size of 10nm - 25nm in the ingot in step S2 of the present invention is as Figure 3 shown. From Figure 3 it can be seen that the proportion of the Mn and Er dispersion phases with a size of 10nm - 25nm is 90%.

[0063] Examples 2 - 3

[0064] Examples 2 - 3 provide a series of 7xxx aluminum alloys, and the contents of their respective components are shown in Table 1. Their preparation methods are the same as those in Example 1.

[0065] Comparative Examples 1 - 2

[0066] Comparative Examples 1 - 2 provide a series of 7xxx aluminum alloys, and the contents of their respective components are shown in Table 1. Their preparation methods are the same as those in Example 1.

[0067] [[ID=3)]]Table 1

[0068] Mass percentage Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2 Zn 9.05％ 9.46％ 8.21％ 9.01％ 9.07％ Mg 3.52％ 3.78％ 3.15％ 3.36％ 3.55％ Cu 0.39％ 0.43％ 0.39％ 0.41％ 0.42％ Mn 0.11％ 0.10％ 0.10％ 0.02％ 0.23％ Er 0.06％ 0.07％ 0.06％ 0.03％ 0.15％ Ti 0.008％ 0.006％ 0.006％ 0.008％ 0.007％ Fe 0.08％ 0.07％ 0.07％ 0.08％ 0.08％ Si 0.06％ 0.06％ 0.06％ 0.06％ 0.06％ Al Balance Balance Balance Balance Balance

[0069] Performance Test

[0070] The metallographic structures of the 7xxx aluminum alloys of Examples 1 - 3 and Comparative Examples 1 - 2 of the present invention are tested, and the results are as Figure 1 shown, where Figure 1 a is Example 1, Figure 1 b is Example 2, Figure 1 c is Comparative Example 1; Figure 1 d is Comparative Example 2; Figure 1 e is Example 3; Figure 1 a comparison Figure 1 with c shows that adding an appropriate amount of Mn + Er can cause recrystallization of the material matrix, control its growth rate, and obtain fine and uniform recrystallized grains (as Figure 1As shown in Figure a); if the contents of these two elements are too low to form sufficient dispersed phases, the recrystallized grains of the material are coarse and uneven (as shown in Figure 1 Figure c). Figure 1 Comparing with Figure a Figure 1 and Figure d, it can be seen that if the addition amounts of Mn + Er are excessive, coarse AlFeMnSi phases and Er-containing phases will be formed, resulting in uneven recrystallization (as shown in Figure 1 Figure d).

[0071] The surfaces of the 7xxx series aluminum alloys of Examples 1 to 3 and Comparative Examples 1 to 2 of the present invention were anodized, and the results are as shown in Figure 2 Figure, Figure 2 where Figure a is Example 1, Figure 2 Figure b is Example 2, Figure 2 Figure c is Comparative Example 1; Figure 2 Figure d is Comparative Example 2, Figure 2 and Figure e is Example 3; Comparing Figure a, Figure 2b, and Figure 2e, it can be seen that reasonably controlling the contents of Zn and Mg and adding appropriate amounts of Mn and Er can maintain a better gloss value and no obvious mottles while improving the strength, meeting the usage requirements of customers; Figure 2 For Figure c and Figure 2d, due to the unreasonable control of the contents of Mn and Er, the grain structure is uneven, resulting in obvious mottles on the surface after anodization, not meeting the usage requirements. Figure 2

[0072] The 7xxx series aluminum alloys prepared in Examples 1 to 3 and Comparative Examples 1 to 2 of the present invention were tested as follows: The results are shown in Table 2.

[0073] Yield strength, tensile strength, elongation: Tested according to GBT 228.1-2010 Tensile testing - Part 1: Method of test at room temperature;

[0074] [[ID=:35]]Average grain size of metal: Tested according to GB / T6394-2017;

[0075] Gloss value: Tested according to GB / T12967.6-2022 Testing methods for anodic oxidation coatings on aluminium and aluminium alloys and organic polymer coatings - Part 6: Colour difference and appearance quality.

[0076] Table 2<00002:46>

[0078] From the data in Table 2, the 7xxx series aluminum alloys of Examples 1 to 3 of the present invention have excellent high strength and good anodic oxidation effect, and can meet the application requirements of 3C products for high strength and high appearance quality of aluminum alloy materials.

[0079] Mass percentage Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2 The above has made a detailed description in connection with the embodiments of the present invention. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the gist of the present invention within the scope of knowledge possessed by those of ordinary skill in the art to which the present invention pertains.

Claims

1. A 7-series aluminum alloy, characterized in that, It comprises the following components by mass percentage: Zn: 7.00% - 10.00%, Mg: 2.00% - 4.00%, Cu: 0.20% - 0.60%, Mn: 0.05% - 0.18%, Er: 0.04% - 0.20%, Ti < 0.05%, Fe ≤ 0.10%, Si ≤ 0.10%, and the balance is Al and unavoidable impurities.

2. The 7-series aluminum alloy according to claim 1, wherein It comprises the following components by mass percentage: Zn: 8.50% - 9.50%, Mg: 2.80% - 3.80%, Cu: 0.30% - 0.50%, Mn: 0.08% - 0.14%, Er: 0.05% - 0.10%, Ti < 0.05%, Fe ≤ 0.10%, Si ≤ 0.10%, and the balance is Al and unavoidable impurities.

3. The 7xxx series aluminum alloy according to claim 1 or 2, characterized in that, In the 7 - series aluminum alloy, 0.10% ≤ Mn + Er ≤ 0.18%.

4. A method for preparing a 7-series aluminum alloy as described in any one of claims 1 to 3, characterized in that, It includes the following steps: S1. Mix Zn, Mg, Cu, Mn, Er, Ti, Fe, Si and Al and carry out melting and casting to obtain a billet. S2. Carry out homogenization treatment on the billet to obtain an ingot blank. S3. Preheat and extrude the ingot blank to obtain an extruded material. S4. Carry out aging treatment on the extruded material to obtain the product.

5. The preparation method according to claim 4, characterized in that, In step S1, the melting temperature is 720°C - 800°C.

6. The preparation method according to claim 4, wherein In step S1, the casting temperature is 680°C - 740°C.

7. The preparation method according to claim 4, characterized in that, In step S2, the steps of the homogenization treatment include: Keep the temperature at 300°C - 360°C for 3h - 5h; keep the temperature at 420°C - 470°C for 4h - 6h; keep the temperature at 490°C - 550°C for 12h - 25h.

8. The preparation method according to claim 4, characterized in that, In step S2, the proportion of the Mn - and - Er dispersed phase with a size of 10nm - 25nm in the ingot blank is ≥ 80wt.%.

9. The preparation method according to claim 4, characterized in that, In step S4, the steps of the aging treatment include: Keep the temperature at 60°C - 120°C for 2h - 20h; then keep the temperature at 130°C - 170°C for 2h - 16h.

10. Application of the 7 - series aluminum alloy according to any one of claims 1 - 3 in the preparation of 3C products.

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