High-iron secondary al-mg-si alloy and method for manufacturing the same

Abstract

The application discloses a kind of high iron content secondary Al-Mg-Si series alloy and its preparation method.The mass composition of Al-Mg-Si secondary aluminum alloy is:0.70~0.90% of Mg,0.60~0.80% of Si,0.20~0.30% of Mn,1.0~1.5% of Fe,0.05~0.20% of Y,0.1~0.4% of Lu,unavoidable impurities,Al is left.The application refines harmful phase α-Al 15 (Fe,Mn)3Si2 by adjusting the composition of alloy,improves the stress corrosion resistance of alloy,greatly inhibits the harm of Fe,obtains high elongation stress corrosion Al-Mg-Si series aluminum alloy containing iron impurities.The prepared alloy has higher elongation,up to 30% after T6 state heat treatment.Also has good stress corrosion resistance,its stress corrosion sensitive index is more than 35%.

Description

Technical Field

[0001] This invention belongs to the field of new materials, specifically relating to a high-strength, high-elongation, stress-corrosion-resistant, iron-containing recyclable aluminum alloy and its manufacturing method. Background Technology

[0002] 6XXX series Al-Mg-Si alloys are heat-treatable aluminum alloys. These alloys possess good formability, high resistance to stress corrosion, excellent surface properties, and weldability, and are primarily used in building profiles, automotive body parts, and aerospace applications. Statistics show that currently only 20% of 6XXX series aluminum alloy scrap is recycled into forging alloys, but this recycling trend is increasing annually. Given the extremely wide range of applications for Al-Mg-Si alloys, they are expected to constitute a major portion of future recycled scrap.

[0003] However, due to the complex sources and high pretreatment difficulty, Al-Mg-Si scrap aluminum often contains different types and qualities of scrap metal. This results in the melt containing not only a large number of non-metallic inclusions but also high levels of soluble impurity elements during the remelting and recycling process. These impurities mainly include H, Li, Si, Cu, Zn, Mn, and Fe. Among them, Fe impurities are the most harmful, often combining with Al and other elements in the alloy to form iron-rich intermetallic compounds, one type being α-Al in the shape of Chinese characters or fish bones. 15 The aluminum alloy has two main phases: (Fe,Mn)3Si2 and β-Al5FeSi / Al9Fe2Si2, which are needle-like or lath-like. These iron-rich phases are mostly hard and brittle, typically impairing the mechanical properties of the alloy to varying degrees, especially its plasticity. Simultaneously, the alloy's corrosion resistance and casting properties are severely affected, reducing the quality of the aluminum alloy. These iron-rich phases have high melting points and excellent thermal stability, making them difficult to eliminate through heat treatment. Therefore, the presence of these iron-rich phases significantly limits the development of the recycled aluminum industry, posing a major challenge to the effective recycling of aluminum alloys.

[0004] Currently, the most direct method to reduce the iron-rich phase in recycled aluminum melt is to remove the Fe element directly from the aluminum melt. Related technologies mainly include gravity sedimentation, centrifugal removal, and electromagnetic separation. However, these methods are often too costly and difficult to implement continuously, thus they are not suitable for actual production.

[0005] Studies have found that rare earth elements can not only refine α-Al dendrites and reduce porosity in aluminum melts, but also improve the size or morphology of acicular iron-rich phases, thus playing a certain role in modification. However, there are many types of rare earth elements, each with different functions. How to effectively improve the performance of secondary aluminum alloys (recycled aluminum alloys) while adding as few rare earth elements as possible remains a challenge. Summary of the Invention

[0006] The purpose of this invention is to overcome at least one deficiency of the prior art and to provide a high-iron secondary Al-Mg-Si alloy and its preparation method.

[0007] The technical solution adopted in this invention is:

[0008] The first aspect of the present invention provides:

[0009] A secondary aluminum alloy with high iron impurity content, comprising the following mass composition: Mg 0.70–0.90%, Si 0.60–0.80%, Mn 0.20–0.30%, Fe 1.0–1.5%, Y 0.05–0.20%, Lu 0.1–0.4%, unavoidable impurities, balance Al.

[0010] In some examples of Al-Mg-Si secondary aluminum alloys, the Fe content is 1.1–1.4%.

[0011] In some examples of Al-Mg-Si secondary aluminum alloys, the Fe:Re mass ratio is 7:(1-4), and Re is the sum of the amounts of Y and Lu added.

[0012] In some examples of Al-Mg-Si secondary aluminum alloys, the total addition of Y and Lu is 0.15 to 0.6%.

[0013] In some examples of Al-Mg-Si secondary aluminum alloys, the Fe:Re mass ratio is 7:(1-4), Re is the sum of the amounts of Y and Lu added, and the total amount of Y and Lu added is 0.15-0.6%.

[0014] In some examples of Al-Mg-Si secondary aluminum alloys, the Fe content is 1.1-1.4%, the Fe:Re mass ratio is 7:(1-4), and Re is the sum of the amounts of Y and Lu added.

[0015] In some examples of Al-Mg-Si secondary aluminum alloys, the Fe content is 1.1 to 1.4%, the Fe:Re mass ratio is 7:(1 to 4), Re is the sum of the added Y and Lu, and the total added Y and Lu is 0.15 to 0.6%.

[0016] In some examples of Al-Mg-Si secondary aluminum alloys, the unavoidable impurity content does not exceed 1%.

[0017] A second aspect of the present invention provides:

[0018] A method for preparing an Al-Mg-Si secondary aluminum alloy with high iron impurity content, wherein the composition of the Al-Mg-Si secondary aluminum alloy is as described in the second aspect of the present invention, includes the following steps:

[0019] S1) Weigh the raw materials according to their composition and smelt them to obtain alloy ingots;

[0020] S2) The alloy ingot is extruded into a profile by an extrusion press, and then immediately immersed in water for quenching to obtain a quenched profile;

[0021] S3) The quenched profile ingot is subjected to solution treatment and artificial aging. After the treatment is completed, it is taken out and air-cooled to obtain the desired alloy.

[0022] In some examples of preparation methods, the solution treatment is carried out at 500–520°C for 0.5–1 h.

[0023] In some examples of preparation methods, the aging treatment is carried out at 150–180°C for 2–4 hours.

[0024] In some examples of preparation methods, the melting temperature is 730–750°C when no magnesium ingot is added, and 660–700°C when magnesium ingot is added.

[0025] In some examples of preparation methods, the solution treatment is carried out at 500–520℃ for 0.5–1 h, and the aging treatment is carried out at 150–180℃ for 2–4 h.

[0026] In some examples of preparation methods, the melting temperature is 730–750°C when no magnesium ingot is added, and 660–700°C when magnesium ingot is added. The solution treatment is carried out at 500–520°C for 0.5–1 h.

[0027] In some examples of preparation methods, the melting temperature is 730–750°C when no magnesium ingot is added, and 660–700°C when magnesium ingot is added. The solution treatment is carried out at 500–520°C for 0.5–1 h, and the aging treatment is carried out at 150–180°C for 2–4 h.

[0028] In some examples of preparation methods, the raw materials are aluminum ingots, magnesium ingots, aluminum-manganese, aluminum-silicon master alloys, and aluminum-rare earth master alloys.

[0029] The beneficial effects of this invention are:

[0030] This invention is the first to propose using a rare earth (Re) combination of Y and Lu to control the formation and morphology of iron impurities. After adding Re, the α-Al dendrites are significantly refined, forming an Al2Si2Re ternary intermetallic compound. This new phase Al2Si2Re in α-Al... 15 The (Fe,Mn)3Si2 phase forms afterward and is distributed in α-Al 15 The surrounding area and surface of the (Fe,Mn)3Si2 phase show a significant refinement of the harmful α-Al phase. 15 (Fe,Mn)3Si2, on the one hand, due to the harmful phase α-Al 15 The (Fe,Mn)3Si2 phase has a large size and aspect ratio, often acting as a crack initiation source and accelerating crack propagation, thus reducing the mechanical properties of the alloy. Therefore, refining the harmful phase can improve strength and elongation. On the other hand, because cracks propagate along the α-Al distributed at grain boundaries... 15 The expansion of the (Fe,Mn)3Si2 phase and the refinement of the harmful phase improve the alloy's resistance to stress corrosion. This significantly suppresses the harmful effects of Fe, resulting in Al-Mg-Si aluminum alloys with high elongation and resistance to iron-containing impurities in stress corrosion. While element Lu has a significant grain-refining effect, it is relatively expensive. Combining Lu with the rare earth element Y creates a synergistic effect, achieving both grain refinement and reduced overall cost. This combined grain-refining effect surpasses that of adding a single rare earth element.

[0031] Some examples of the high-iron secondary Al-Mg-Si alloys of this invention exhibit high elongation, reaching up to 30% after T6 heat treatment. They also demonstrate good resistance to stress corrosion, with a stress corrosion susceptibility index exceeding 35%.

[0032] Some examples of this invention overcome the bottleneck problem of difficult recycling of traditional 6XXX aluminum alloys due to high iron impurities by implementing effective and feasible composite microalloying methods and matching reasonable heat treatment processes, while improving the mechanical and stress corrosion resistance properties of secondary aluminum alloys. Attached Figure Description

[0033] Figure 1 The three-dimensional morphologies of alloys with different Re contents are: (a) 0; (b) 0.15Re; (c) 0.2Re; (d) 0.3YRe. Detailed Implementation

[0034] The first aspect of the present invention provides:

[0035] A secondary aluminum alloy with high iron impurity content, comprising the following mass composition: Mg 0.70–0.90%, Si 0.60–0.80%, Mn 0.20–0.30%, Fe 1.0–1.5%, Y 0.05–0.20%, Lu 0.1–0.4%, unavoidable impurities, balance Al.

[0036] In some examples of Al-Mg-Si secondary aluminum alloys, the Fe content is 1.1% to 1.4%. This is the range of Fe content in multiple secondary alloys.

[0037] In some examples of Al-Mg-Si secondary aluminum alloys, the Fe:Re mass ratio is 7:(1-4), where Re is the sum of the amounts of Y and Lu added. By controlling the ratio of the two, the relatively expensive Y and Lu can be added more precisely, reducing costs while ensuring material performance.

[0038] In some examples of Al-Mg-Si secondary aluminum alloys, the total addition of Y and Lu is 0.15 to 0.6%.

[0039] In some examples of Al-Mg-Si secondary aluminum alloys, the Fe:Re mass ratio is 7:(1-4), Re is the sum of the amounts of Y and Lu added, and the total amount of Y and Lu added is 0.15-0.6%.

[0040] In some examples of Al-Mg-Si secondary aluminum alloys, the Fe content is 1.1-1.4%, the Fe:Re mass ratio is 7:(1-4), and Re is the sum of the amounts of Y and Lu added.

[0041] In some examples of Al-Mg-Si secondary aluminum alloys, the Fe content is 1.1 to 1.4%, the Fe:Re mass ratio is 7:(1 to 4), Re is the sum of the added Y and Lu, and the total added Y and Lu is 0.15 to 0.6%.

[0042] In some examples of Al-Mg-Si secondary aluminum alloys, the unavoidable impurity content does not exceed 1%. The fewer the impurities, the better it is to obtain Al-Mg-Si secondary aluminum alloys with stable quality.

[0043] A second aspect of the present invention provides:

[0044] A method for preparing an Al-Mg-Si secondary aluminum alloy with high iron impurity content, wherein the composition of the Al-Mg-Si secondary aluminum alloy is as described in the second aspect of the present invention, includes the following steps:

[0045] S1) Weigh the raw materials according to their composition and smelt them to obtain alloy ingots;

[0046] S2) The alloy ingot is extruded into a profile by an extrusion press, and then immediately immersed in water for quenching to obtain a quenched profile;

[0047] S3) The quenched profile ingot is subjected to solution treatment and artificial aging. After the treatment is completed, it is taken out and air-cooled to obtain the desired alloy.

[0048] Solid solution treatment can make the elemental distribution more uniform, which is beneficial to improving the homogeneity of the material. In some examples of preparation methods, the solid solution treatment is carried out at 500-520℃ for 0.5-1h.

[0049] Aging treatment can better promote grain formation and stabilization. In some preparation methods, aging treatment involves holding at 150–180℃ for 2–4 hours.

[0050] In some examples of preparation methods, the melting temperature is 730–750°C without magnesium ingots and 660–700°C with magnesium ingots. By adding magnesium ingots at a lower temperature, magnesium can be more uniformly dispersed in the alloy, which is beneficial to improving the overall performance of the alloy.

[0051] In some examples of preparation methods, the solution treatment is carried out at 500–520℃ for 0.5–1 h, and the aging treatment is carried out at 150–180℃ for 2–4 h.

[0052] In some examples of preparation methods, the melting temperature is 730–750°C when no magnesium ingot is added, and 660–700°C when magnesium ingot is added. The solution treatment is carried out at 500–520°C for 0.5–1 h.

[0053] In some examples of preparation methods, the melting temperature is 730–750°C when no magnesium ingot is added, and 660–700°C when magnesium ingot is added. The solution treatment is carried out at 500–520°C for 0.5–1 h, and the aging treatment is carried out at 150–180°C for 2–4 h.

[0054] The types of raw materials can be adjusted as needed. In some examples of preparation methods, the raw materials are aluminum ingots, magnesium ingots, aluminum-manganese, aluminum-silicon master alloys, and aluminum-rare earth master alloys. Aluminum ingots can be prepared from recycled aluminum.

[0055] The present invention will now be described in detail with reference to embodiments, comparative examples, and experimental data. Unless otherwise specified, all percentages in the composition are mass percentages.

[0056] The alloy chemical composition by mass percentage in each embodiment is as follows: Mg 0.70–0.90%, Si 0.60–0.80%, Mn 0.20–0.30%, Fe 1.0–1.5%, Re 0.15–0.6%. The raw materials are pure Al and Mg ingots, with the addition of Al-10Fe, Al-10Y, Al-30Si master alloys, and a secondary Al-0.68Mg-0.58Si-0.55Fe-0.26Mn alloy.

[0057] The multi-component refining agent and degassing agent are the commonly used NaCl-KCl composite refining agent and C2Cl6 degassing agent in this field. The mass ratio of the composite refining agent to the smelting materials is 2:100. The composition of the multi-component composite refining agent includes: 20wt% NaCl, 20wt% KCl, 35wt% NaF, and 25wt% LiF; the mass ratio of the degassing agent to the smelting materials is 1:100. After degassing, the aluminum liquid is skimmed off using a slag skimmer, and the skimmed liquid must be collected and treated. When the purity of the raw materials is low and there are many impurities, the dosage of the multi-component refining agent and degassing agent needs to be appropriately increased.

[0058] For ease of comparison, the impurities in each example are 0.5%. Example 1

[0059] 1) According to the weight percentage of the constituent elements, take Mg: 0.81%, Si: 0.75%, Mn: 0.24%, Fe: 1.1%, Re: 0.15%, of which Y is 0.05%, Lu is 0.1%, and the balance is Al; prepare aluminum ingots, aluminum master alloys and rare earth alloys, melt and mix the raw materials at 730-750℃, and then cool down to 660-700℃ and add magnesium ingots to obtain the final alloy ingot;

[0060] 2) The prepared alloy ingot was subjected to solution treatment (500-520℃ for 1 hour) and aging treatment (160℃ for 2-4 hours). The sample was then removed and air-cooled. Example 2

[0061] 1) According to the weight percentage of the constituent elements, take Mg: 0.85%, Si: 0.68%, Mn: 0.21%, Fe: 1.1%, Re: 0.20%, of which Y is 0.06%, Lu is 0.14%, and the balance is Al; prepare aluminum ingots, aluminum master alloys and rare earth alloys, melt and mix the raw materials at 730-750℃, and then cool down to 660-700℃ and add magnesium ingots to obtain the final alloy ingot;

[0062] 2) The prepared alloy ingot was subjected to solution treatment (500-520℃ for 1 hour) and aging treatment (160℃ for 2-4 hours). The sample was then removed and air-cooled. Example 3

[0063] 1) According to the weight percentage of the constituent elements, take Mg: 0.74%, Si: 0.62%, Mn: 0.20%, Fe: 1.1%, Re: 0.30%, of which Y is 0.1%, Lu is 0.2%, and the balance is Al; prepare aluminum ingots, aluminum master alloys and rare earth alloys, melt and mix the raw materials at 730-750℃, and then cool down to 660-700℃ and add magnesium ingots to obtain the final alloy ingot;

[0064] 2) The prepared alloy ingot was subjected to solution treatment (500-520℃ for 1 hour) and aging treatment (160℃ for 2-4 hours). The sample was then removed and air-cooled. Example 4

[0065] 1) According to the weight percentage of the constituent elements, take Mg: 0.80%, Si: 0.62%, Mn: 0.25%, Fe: 1.1%, Re: 0.40%, of which Y is 0.1%, Lu is 0.3%, and the balance is Al; prepare aluminum ingots, aluminum master alloys and rare earth alloys, melt and mix the raw materials at 730-750℃, and then cool down to 660-700℃ and add magnesium ingots to obtain the final alloy ingot;

[0066] 2) The prepared alloy ingot was subjected to solution treatment (500-520℃ for 1 hour) and aging treatment (160℃ for 2-4 hours). The sample was then removed and air-cooled. Example 5

[0067] 1) According to the weight percentage of the constituent elements, take Mg: 0.75%, Si: 0.69%, Mn: 0.21%, Fe: 1.1%, Re: 0.50%, of which Y is 0.15%, Lu is 0.35%, and the balance is Al; prepare aluminum ingots, aluminum master alloys and rare earth alloys, melt and mix the raw materials at 730-750℃, and then cool down to 660-700℃ and add magnesium ingots to obtain the final alloy ingot;

[0068] 2) The prepared alloy ingot was subjected to solution treatment (500-520℃ for 1 hour) and aging treatment (160℃ for 2-4 hours). The sample was then removed and air-cooled. Example 6

[0069] 1) According to the weight percentage of the constituent elements, take Mg: 0.72%, Si: 0.66%, Mn: 0.27%, Fe: 1.1%, Re: 0.60%, of which Y is 0.24%, Lu is 0.36%, and the balance is Al; prepare aluminum ingots, aluminum master alloys and rare earth alloys, melt and mix the raw materials at 730-750℃, and then cool down to 660-700℃ and add magnesium ingots to obtain the final alloy ingot;

[0070] 2) The prepared alloy ingot was subjected to solution treatment (500-520℃ for 1 hour) and aging treatment (160℃ for 2-4 hours). The sample was then removed and air-cooled. Comparative Example 1

[0071] 1) According to the weight percentage of the constituent elements, take Mg: 0.79%, Si: 0.63%, Mn: 0.23%, Fe: 1.1%, Re: 0%, with the balance being Al; prepare aluminum ingots, aluminum master alloys and rare earth alloys, melt them at 730-750℃ to fully melt and mix the raw materials, and then cool them down to 660-700℃ to add magnesium ingots to obtain the final alloy ingot;

[0072] 2) The prepared alloy ingot was subjected to solution treatment (500-520℃ for 1 hour) and aging treatment (160℃ for 2-4 hours). The sample was then removed and air-cooled. Comparative Example 2

[0073] 1) According to the weight percentage of the constituent elements, take Mg: 0.70%, Si: 0.61%, Mn: 0.22%, Fe: 1.1%, Re: 1.0%, of which Y is 0.3%, Lu is 0.7%, and the balance is Al; prepare aluminum ingots, aluminum master alloys and rare earth alloys, melt and mix the raw materials at 730-750℃, and then cool down to 660-700℃ and add magnesium ingots to obtain the final alloy ingot;

[0074] 2) The prepared alloy ingot was subjected to solution treatment (500-520℃ for 1 hour) and aging treatment (160℃ for 2-4 hours). The sample was then removed and air-cooled.

[0075] Comparison of the properties of Al-Mg-Si-Fe-Re recyclable aluminum alloys with different Re contents

[0076] Mechanical and corrosion properties of the high-speed rail Al-Mg-Si-Fe-Re alloy plates obtained in the examples and comparative examples were tested. The strength and elongation were determined according to GB / T 228.1-2010 "Metallic materials, tensile testing—Part 1: Tests at room temperature," and the results are shown in Table 1. The corrosion performance was tested according to national standard GB / T15970.7-2017. Slow strain rate tensile testing was used to study the alloy's stress corrosion cracking susceptibility, and the results are shown in Table 2.

[0077] Table 1. Mechanical property test results

[0078]

[0079] 1) Comparing Examples 1 to 6, it can be seen that as the amount of Re increases, the strength and elongation of the alloy first increase and then decrease;

[0080] 2) The Re content in Comparative Examples 1 and 2 was outside the specified range, and the mechanical properties of the alloys decreased significantly.

[0081] Figure 1 The images show the microstructures of the high-speed iron Al-Mg-Si-Fe-Re alloys prepared in Comparative Example 1 and Examples 1-3. It can be seen that with the increase of Re, the harmful α-Al phase... 15 (Fe,Mn)3Si2 from long fishbone-shaped ( Figure 1 a) transforms into shorter petal-like shapes ( Figure 1 b, c), eventually transforming into irregular strip-shaped bars ( Figure 1 d), its size continuously decreases. The Al2Si2Re phase formed after the addition of Re is distributed in the harmful α-Al phase. 15 The presence of (Fe,Mn)3Si2 around or attached to the surface greatly restricts the nucleation and growth of harmful phases, thereby refining the harmful phases and improving the mechanical properties of the alloy.

[0082] Table 2 Results of stress corrosion test

[0083]

[0084] 1) Comparing Examples 1 to 3, it can be seen that the corrosion resistance of the alloy improves with the increase of Re content;

[0085] 2) The Re content in Comparative Example 1 was outside the specified range, and the corrosion performance of the alloy decreased significantly.

[0086] The above is a further detailed description of the present invention and should not be considered as a limitation on the specific implementation of the present invention. For those skilled in the art, simple deductions or substitutions without departing from the concept of the present invention are all within the protection scope of the present invention.

Claims

1. A secondary aluminum alloy with high iron impurity content, comprising the following mass composition: Mg 0.70–0.90%, Si 0.60–0.80%, Mn 0.20–0.30%, Fe 1.0–1.5%, Y 0.05–0.20%, Lu 0.1–0.4%, unavoidable impurities, balance Al, Fe:Re mass ratio = 7:(1–4), Re being the sum of Y and Lu additions, wherein the Al2Si2Re phase formed after the addition of Re is distributed in the harmful α-Al phase. 15 (Fe,Mn)3Si2 is present around or attached to the surface. After heat treatment in the T6 state, the elongation can reach up to 30%, and the stress corrosion susceptibility index is above 35%.

2. The Al-Mg-Si secondary aluminum alloy according to claim 1, characterized in that, The Fe content is 1.1%–1.4%.

3. The Al-Mg-Si secondary aluminum alloy according to claim 1, characterized in that, The content of unavoidable impurities shall not exceed 1%.

4. The Al-Mg-Si secondary aluminum alloy according to any one of claims 1 to 3, characterized in that, The total addition amount of Y and Lu is 0.15-0.6%.

5. A method for preparing an Al-Mg-Si secondary aluminum alloy with high iron impurity content, wherein the composition of the Al-Mg-Si secondary aluminum alloy is as described in any one of claims 1 to 4, comprising the following steps: S1) Weigh the raw materials according to their composition and smelt them to obtain alloy ingots; S2) The alloy ingot is extruded into a profile by an extrusion press, and then immediately immersed in water for quenching to obtain a quenched profile; S3) The quenched profile ingot is subjected to solution treatment and artificial aging. After the treatment is completed, it is taken out and air-cooled to obtain the desired alloy.

6. The preparation method according to claim 5, characterized in that, Solution treatment involves holding the solution at 500–520℃ for 0.5–1 hour.

7. The preparation method according to claim 5 or 6, characterized in that, The aging treatment involves holding the temperature at 150–180℃ for 2–4 hours.

8. The preparation method according to claim 5 or 6, characterized in that, The smelting temperature is 730-750℃ when no magnesium ingots are added, and 660-700℃ when magnesium ingots are added.

9. The preparation method according to claim 5 or 6, characterized in that, The raw materials are aluminum ingots, magnesium ingots, aluminum-manganese, aluminum-silicon master alloys, and aluminum-rare earth master alloys.

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