A method of controlling alfe si phase in 6000-series aluminum alloy and aluminum alloy
By controlling the cooling rate and hot rolling process, the problem of AlFeSi phase coarsening in 6000 series aluminum alloys was solved, improving the strength and ductility of the material and achieving a comprehensive performance improvement of the aluminum alloy.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANDONG UNIV OF TECH
- Filing Date
- 2023-11-23
- Publication Date
- 2026-05-29
Smart Images
Figure CN117488117B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of metal smelting and heat treatment technology, and in particular to a method for controlling the AlFeSi phase in 6000 series aluminum alloys and the aluminum alloy itself. Background Technology
[0002] 6000 series aluminum alloys are aluminum alloys with magnesium and silicon as the main alloying elements and Mg2Si phase as the strengthening phase. They belong to heat-treatable aluminum alloys. The alloys have advantages such as moderate strength, high corrosion resistance, no tendency for stress corrosion cracking, good formability and processing performance.
[0003] Lightweighting of automobiles is a crucial research direction for future automotive development worldwide, primarily following three paths: material lightweighting, improved manufacturing processes, and optimized structural design, with material lightweighting receiving the most attention. Currently, the main aluminum alloys used in automobiles are 5000 and 6000 series alloys. While 6000 series alloys combine the advantages of both 5000 and 4000 series alloys, they still suffer from lower strength, making it difficult to achieve lightweighting of load-bearing structural components and thus failing to fully realize the lightweighting advantages of aluminum alloys. The formation of the AlFeSi phase during the melting and solidification process of 6000 series aluminum alloys is one of the factors limiting its performance.
[0004] The AlFeSi phase is an intermetallic compound formed during solidification. These compounds have high melting points, are large in size, and are relatively brittle. They remain in the material throughout subsequent heat treatment and processing of aluminum alloys and cannot be dissolved into the matrix during solution treatment. If a large number of coarse intermetallic compounds are distributed along the grain boundaries of aluminum alloys, it will reduce the grain boundary bonding strength and decrease the fracture toughness of the material. Therefore, it is necessary to study a method for controlling the AlFeSi phase in 6000 series aluminum alloys and the study of aluminum alloys in general. Summary of the Invention
[0005] The purpose of this invention is to provide a method and an aluminum alloy for controlling the AlFeSi phase in 6000 series aluminum alloys. The method first controls the cooling rate during the solidification process of the 6000 series aluminum alloy to reduce the formation of the α-AlFeSi phase and promote the formation of the β-AlFeSi phase. Residual stress is removed by controlling the cooling rate, and finally, the alloy is air-cooled to room temperature for complete solidification, forming a 6000 series aluminum alloy containing only low-stress or even stress-free β-AlFeSi phases, thus avoiding the adverse effects of large-sized α-AlFeSi phases on material properties. Subsequently, homogenization treatment transforms the β-AlFeSi phase into the α-AlFeSi phase, reducing the proportion of Fe atoms occupying Si atoms and releasing Si atoms. Warm rolling refines the grains, fully breaking down large grains and forming fine or even ultrafine grain structures, improving the overall properties of the material, such as strength and ductility.
[0006] To achieve the above-mentioned objectives of this invention, the following technical solution is adopted:
[0007] A method for controlling the AlFeSi phase in 6000 series aluminum alloys includes the following steps:
[0008] Step 1: Sequentially add materials to melt 6000 series aluminum alloy, and perform staged cooling during the solidification process of the 6000 series aluminum alloy solution;
[0009] Step 2: The solidified 6000 series aluminum alloy billet is first subjected to homogenization heat treatment, and then warm rolled.
[0010] Further: In step one, the melting temperature is heated to 700~760℃ in one go and held for 30~60 minutes.
[0011] Preferably, the temperature is raised to 730℃~750℃ in one go and held for 50~60 minutes.
[0012] Further: In step one, the staged cooling process first involves rapid cooling at a rate of 5~35℃ / s to 560~590℃, then cooling at a rate of 20~120℃ / h to 240~280℃, and finally air cooling to room temperature.
[0013] Preferably, rapid cooling is performed at a rate of 15~30℃ / s to cool to 565~575℃.
[0014] Preferably, the temperature is cooled to 240℃~260℃ at a rate of 30~60℃ / h, and finally air-cooled to room temperature.
[0015] Further: In step two, the homogenization heat treatment involves heating to 530-560℃ at a heating rate of 5-10℃ / min and holding for 2-4 hours. After holding, the temperature is cooled to 290-370℃ for warm rolling.
[0016] Preferably, the temperature is increased to 550-560℃ at a heating rate of 7-10℃ / min and held for 3-4 hours.
[0017] Preferably, the rolling process is carried out at 300~340℃, using a rolling method with decreasing passes, and the rolling amount per pass exceeds 50% to refine the grains.
[0018] The advantages of this invention are as follows:
[0019] This invention provides a method and an aluminum alloy for controlling the AlFeSi phase in 6000 series aluminum alloys. By employing a staged cooling, homogenization treatment, and temperature rolling synergistic control method, the existence state, grain size, and orientation of the AlFeSi phase are regulated. This avoids the growth of the α-AlFeSi phase size and forms a stable and fine AlFeSi phase, thereby improving the overall properties of the material, such as strength and ductility, and reducing the occupation of Si elements by Fe elements in the aluminum alloy. This effectively controls the AlFeSi phase in 6000 series aluminum alloys.
[0020] This method requires no modification to the production process or equipment, is simple and easy to implement, and produces 6000 series aluminum alloy thick plates with significantly improved comprehensive mechanical properties, making it suitable for industrial production. Attached Figure Description
[0021] Figure 1 This is a schematic diagram of a method for controlling the AlFeSi phase in 6000 series aluminum alloys according to the present invention;
[0022] Figure 2 This is a schematic diagram of the traditional 6000 series aluminum alloy production method;
[0023] Figure 3 This is a microstructure diagram of the α-AlFeSi phase obtained after solidification in Comparative Example 1.
[0024] Figure 4 This is a microstructure diagram of the β-AlFeSi phase obtained after solidification in Example 1;
[0025] Figure 5 This is a grain structure diagram of the 6000 series aluminum alloy prepared in Example 1;
[0026] Figure 6 This is a grain structure diagram of the 6000 series aluminum alloy prepared in Example 3;
[0027] Figure 7 This is a grain structure diagram of the 6000 series aluminum alloy prepared by conventional process in Comparative Example 1;
[0028] Figure 8 This is a statistical comparison chart of grain size between the examples and the comparative examples. Implementation
[0029] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention.
[0030] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.
[0031] This invention provides a method for controlling the AlFeSi phase in 6000 series aluminum alloys, comprising the following steps:
[0032] The ingredients are added sequentially, then heated to 700-760℃ and held for 30-60 minutes. The mixture is then rapidly cooled to 560-590℃ at a rate of 5-35℃ / s, followed by stress relief treatment at 20-120℃ / h to 240-280℃, and air-cooled to room temperature. The mixture is then reheated to 530-560℃ and held for 2-4 hours for homogenization, and finally warm-rolled to refine the grains. Example 1
[0033] A method for controlling the AlFeSi phase in 6000 series aluminum alloys includes the following steps:
[0034] Step 1: Add materials sequentially and heat to 730℃ to melt 6000 series aluminum alloy, hold for 55 minutes, cool in stages at 15℃ / s to 570℃ and 60℃ / h to 260℃, and finally air cool to room temperature until it is completely solidified.
[0035] Step 2: The 6000 series aluminum alloy billet obtained in Step 1 is heated to 550℃ in a heating furnace at a heating rate of 8℃ / min and held for 3 hours. After being taken out of the furnace, it is air-cooled to 320℃ for warm rolling. A multi-pass rolling method is adopted, with the reduction rate decreasing in 3 to 5 passes. The rolling amount in each pass exceeds 50%, and the final rolling amount is 80%.
[0036] The 6000 series aluminum alloy produced by the method of this embodiment has higher strength, toughness and grain size than the sample produced by conventional melting and solidification methods, with an average grain size of 14.84 μm.
[0037] The performance indicators of the obtained 6000 series aluminum alloy are shown in Table 1. Example 2
[0038] A method for controlling the AlFeSi phase in 6000 series aluminum alloys includes the following steps:
[0039] Step 1: Add materials sequentially and heat to 730℃ to melt 6000 series aluminum alloy, hold for 55 minutes, cool in stages at 20℃ / s to 570℃ and 45℃ / h to 260℃, and finally air cool to room temperature until it is completely solidified.
[0040] Step 2: The 6000 series aluminum alloy billet obtained in Step 1 is heated to 550℃ in a heating furnace at a heating rate of 8℃ / min and held for 3 hours. After being taken out of the furnace, it is air-cooled to 320℃ and then warm-rolled using a multi-pass rolling method. The reduction rate of each pass is reduced in a manner of 3 to 5 passes, and the rolling amount of each pass exceeds 50%, with a final rolling amount of 80%.
[0041] The 6000 series aluminum alloy produced by the method of this embodiment has higher strength, toughness and grain size than the sample produced by conventional melting and solidification methods, with an average grain size of 12.63 μm.
[0042] The performance indicators of the obtained 6000 series aluminum alloy are shown in Table 1. Example 3
[0043] A method for controlling the AlFeSi phase in 6000 series aluminum alloys includes the following steps:
[0044] Step 1: Add materials sequentially and heat to 730℃ to melt 6000 series aluminum alloy, hold for 55 minutes, cool in stages at 30℃ / s to 570℃ and 30℃ / h to 260℃, and finally air cool to room temperature until it is completely solidified.
[0045] Step 2: The 6000 series aluminum alloy billet obtained in Step 1 is heated to 550℃ in a heating furnace at a heating rate of 8℃ / min and held for 3 hours. After being taken out of the furnace, it is air-cooled to 320℃ for warm rolling. A multi-pass rolling method is adopted, with the reduction rate decreasing in 3 to 5 passes. The rolling amount in each pass exceeds 50%, and the final rolling amount is 80%.
[0046] The 6000 series aluminum alloy produced by the method of this embodiment has higher strength, toughness and grain size than the sample produced by conventional melting and solidification methods, with an average grain size of 11.88 μm.
[0047] The performance indicators of the obtained 6000 series aluminum alloy are shown in Table 1. Comparative Example 1
[0048] A traditional 6000 series aluminum alloy smelting process is basically the same as step one in Example 1, except that after melting and holding at a certain temperature, the cooling rate is not controlled and the alloy is directly air-cooled to room temperature until it is completely solidified, and the average grain size reaches 71.57 μm.
[0049] The performance indicators of the obtained 6000 series aluminum alloy are shown in Table 1. Comparative Example 2
[0050] A traditional smelting process for 6000 series aluminum alloy involves heating the 6000 series aluminum alloy billet obtained in Comparative Example 1 to 550°C in a heating furnace at a heating rate of 8°C / min and holding it at that temperature for 3 hours. After exiting the furnace, the billet is air-cooled to 320°C for warm rolling. A multi-pass rolling method is adopted, with the reduction rate decreasing in 3 to 5 passes. The rolling amount in each pass exceeds 50%, and the final rolling amount is 80%, with an average grain size of 31.28 μm.
[0051] The performance indicators of the obtained 6000 series aluminum alloy are shown in Table 1.
[0052] Table 1 Performance Indicators of 6000 Series Aluminum Alloys
[0053] Example Yield strength (MPa) Tensile strength (MPa) Elongation (%) Grain size (%) AlFeSi phase Example 1 286 357 10.7 9 α-AlFeSi Example 2 293 361 10.8 9 α-AlFeSi Example 3 308 382 11.6 10 α-AlFeSi Comparative Example 1 216 272 7.8 6 α-AlFeSi Comparative Example 2 268 321 9.6 8 α-AlFeSi
[0054] By comparing Comparative Example 1 and Comparative Example 2, it can be seen that the aluminum alloy prepared in Comparative Example 1, without controlling the cooling rate during solidification, without homogenization treatment, and without warm rolling, has a yield strength and tensile strength far lower than the sample prepared in this invention, and its elongation is only 70% of that of the aluminum alloy in this invention. Furthermore, the final AlFeSi phase obtained is also a coarse α-AlFeSi phase, while this invention can obtain a fine α-AlFeSi phase, and its aluminum alloy matrix grain size is also much lower than that of this invention. Although Comparative Example 2 underwent homogenization treatment and warm rolling, the solidification rate of the aluminum alloy was also not controlled. Although the final α-AlFeSi phase was finer than that of Comparative Example 1, it had higher residual stress, and its mechanical properties and grain size were only slightly higher than those of Comparative Example 1. Its overall performance was far lower than that of this invention.
[0055] Although the invention has been illustrated and described with reference to specific embodiments, it should be understood that many other changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, it is intended that all such changes and modifications falling within the scope of the invention be included in the appended claims.
Claims
1. A method for controlling the AlFeSi phase in 6000 series aluminum alloys, characterized in that, Includes the following steps: 1) Batching and smelting: Batchute the raw materials according to the following mass percentages: Si: 1.0-1.5%, Mg: 0.25-0.6%, Cu: <0.20%, Mn: <0.20%, Fe: <0.50%, Cr: <0.10%, Ti: <0.15%, with the remainder being Al; after adding the raw materials, control the smelting temperature at 700℃~760℃ and hold for 30~60 minutes. 2) Solidification: After melting, the material is rapidly cooled at a rate of 5~35℃ / s to 560~590℃, then slowly cooled at a rate of 20~120℃ / h to 240℃~280℃, and finally air-cooled to room temperature. 3) Homogenization treatment: After solidification, the aluminum ingot is heated to 530~560℃ and held for 2~4 hours to perform homogenization treatment; 4) Warm rolling: After homogenization heat treatment, cool to 290~370℃ for warm rolling. Use a decreasing reduction rate per pass for 3~5 passes of deformation, with each pass deforming more than 30%. Warm rolling refines the grains.
2. The method for controlling the AlFeSi phase in 6000 series aluminum alloys according to claim 1, characterized in that, Step 3) Heat to 530-560℃ at a heating rate of 5-10℃ / min and hold for 2-4 hours.