Method for regulating and controlling structure and performance of high-Fe-content 6016 secondary aluminum alloy

Abstract

The invention belongs to the field of wrought aluminum alloy regeneration and recovery, and discloses a method for regulating and controlling the structure and performance of a high-Fe-content 6016 regenerated aluminum alloy. The method comprises the following steps: 1) melting a 6016 aluminum alloy with high Fe content, adding a Cr-containing intermediate alloy, uniformly mixing, standing, and adding Sn to obtain a microalloyed melt; (2) the melt passes through a snake-shaped pouring gate and then enters a mold, and casting is conducted to form a cast ingot; and (3) the cast ingot is subjected to homogenizing annealing treatment, air cooling is conducted after hot rolling, then cold rolling, high-temperature solid solution treatment, cooling, natural aging and artificial aging treatment are conducted, and the regenerated aluminum alloy is obtained. According to the method, primary alpha-Al grains in the 6016 regenerated alloy are efficiently refined, the roundness is improved, and the Fe-rich phase form is effectively modified into a small Chinese character shape from a thick long needle shape. The prepared regenerated aluminum alloy is excellent in mechanical property, the harm of the impurity element Fe to the 6016 regenerated aluminum alloy is remarkably reduced, and high-quality utilization of the regenerated aluminum alloy is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of recycling and high-quality utilization of deformed aluminum alloys, and specifically relates to a method for regulating the structure and properties of high-Fe content 6016 recycled aluminum alloy. Background Art

[0002] In the context of dual carbon emissions, the demand for improving vehicle fuel efficiency and reducing emissions is increasing. Lightweighting is a key approach to achieving energy conservation and consumption reduction. Aluminum alloys, with their lightweight and high specific strength, are becoming increasingly widely used in automotive components. Heat-treatable 6000 series (Al-Mg-Si) alloys have become the mainstream, replacing steel sheets in components such as engine hoods. 6016 aluminum alloy, with its low strength and high formability in the T4 state (supersaturated solid solution), offers excellent surface quality after stamping and excellent hardening response after paint bake (PB), making it widely used in automotive exterior panels.

[0003] With the continued growth in automobile sales and the gradual scrapping of vehicles after exceeding their service life (approximately 10-20 years), there will be a peak in the recycling of automotive aluminum. However, during the recycling process, impurity elements such as Fe are inevitably introduced, affecting the performance and use of the alloy. High Fe content will form coarse alloy phases, seriously compromising the alloy's performance and becoming a key issue in the grade-preserving recycling and reuse of recycled 6000 series aluminum alloys. Based on this, it is of great significance to conduct research on the fundamental issues related to the regulation of Fe-rich phases in high-Fe content Al-Mg-Si alloys.

[0004] Since Fe is an impurity element that is difficult to avoid in aluminum alloys, there is a certain Fe content (0.1-0.2%) in the 6000 series alloys. In particular, after regeneration and recovery, the Fe content is further increased, even higher than 0.5%. At this time, it can be regarded as an Al-Mg-Si-Fe alloy. During the solidification process, a variety of Fe-containing phases will be formed, and different Fe-containing phases will also transform into each other. Since the solid solubility of Fe in the Al matrix is extremely low (only ~0.015wt.% at 540°C) and the diffusion rate is slow, the Fe-containing phase is generally difficult to fully dissolve back through heat treatment, which is not conducive to improving the mechanical properties of the material.

[0005] Chinese patent application number CN202411111251.7 discloses a method for reducing the harmful effects of iron in 6101 aluminum alloy. The invention involves melting the 6101 aluminum alloy in a smelting furnace, adding an Al-Si master alloy to the melt, and stirring to obtain a uniform 6101 aluminum alloy melt. Refining agents are then added to the melt, followed by purification with argon gas, before the melt is cast into aluminum alloy ingots. Finally, the aluminum alloy ingots are sequentially heat treated. This patent application essentially aims to improve and enhance the performance of high-Fe 6101 aluminum alloys by increasing the Si content and altering the Fe phase. Chinese patent application number CN202411258868.1 discloses a method for modifying a melt containing an iron-rich phase. This method involves heating an aluminum alloy melt to 700-1200°C and holding the temperature for 10-60 minutes. The iron-rich phase in the melt is completely melted, and a large number of high-melting-point spherical intermetallic compounds are introduced into the aluminum alloy melt as a modifier. These compounds serve as nucleation sites for the Fe phase, achieving efficient modification and control of the Fe-rich phase morphology. For Fe-rich recycled 6016 alloy, Si content is very sensitive to plasticity and paint hardening. High-temperature treatment can lead to excessive burnout of Mg, ultimately affecting aging strengthening.

[0006] Existing deformed aluminum alloys generally contain Fe-rich phases that fail to be effectively modified and refined. The Fe-rich phase modifying elements affect the aging response of Al-Mg-Si-based deformed aluminum alloys, making it difficult to effectively improve their strength. To address the above problems, the present invention achieves efficient refinement of primary α-Al grains in 6016 recycled alloys by coordinating melt microalloying and modification with a serpentine channel preparation process, improving roundness and effectively transforming the Fe-rich phase morphology from a coarse, long needle shape to a fine, Chinese character shape. The recycled aluminum alloy prepared by the synergistic microalloying and serpentine channel has excellent mechanical properties, significantly reducing the harm of the impurity element Fe to the 6016 recycled aluminum alloy, and achieving high-quality utilization of the recycled aluminum alloy. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, the present invention aims to provide a method for regulating the microstructure and properties of high-Fe 6016 recycled aluminum alloy. This method, based on alloying melt processing technology, microalloys the melt with Cr / Sn, and simultaneously utilizes a serpentine channel preparation technique. This allows the alloy to undergo homogenization, rolling deformation, and solutionizing followed by aging, resulting in excellent strength and ductility at peak aging, as well as a faster aging response.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] A method for regulating the microstructure and properties of a high-Fe content 6016 recycled aluminum alloy comprises the following steps:

[0010] 1) Microalloying treatment: melt the 6016 aluminum alloy with high Fe content, add the Cr-containing master alloy, mix well, let it stand, and then add Sn to obtain a microalloyed melt;

[0011] 2) Preparation using a serpentine runner: The melt passes through the serpentine runner and then enters the mold to be cast into an ingot;

[0012] 3) The ingot is subjected to homogenization annealing treatment, air-cooled after hot rolling, and then cold-rolled to obtain a plate;

[0013] 4) subjecting the plate to high-temperature solid solution treatment and cooling to obtain a supersaturated solid solution; subjecting the supersaturated solid solution to natural aging and artificial aging treatment to obtain a deformed aluminum alloy.

[0014] In step 1), the microalloyed melt needs to be supplemented with Mg to compensate for the burnout. Mg is added in the form of a master alloy, and Mg is added together with Sn. The master alloy of Mg is a master alloy Al-10Mg, that is, an Al-Mg alloy with a mass fraction of 10%.

[0015] The standing time in step 1) is 4 to 10 minutes.

[0016] The microalloying of 6016 aluminum alloy with high Fe content, Cr and Sn results in the following mass contents in the product deformed aluminum alloy:

[0017] Mg: 0.45-0.6%;

[0018] Si: 1.0-1.2%;

[0019] Fe: 0.2%~0.6%;

[0020] Cr: 0.1-0.3%, preferably 0.15-0.3%;

[0021] Sn: 0.08 to 0.15%, preferably 0.1 to 0.15%.

[0022] The remainder of the product deformed aluminum alloy is Al or Al and other impurities.

[0023] The Cr-containing master alloy in step 1) is an Al-20Cr or Al-10Cr master alloy. The amount of Mg burned out is supplemented by 10-20% (for example, 15%) of the Mg content in the product deformed aluminum alloy.

[0024] The melting temperature in step 1) is 740°C to 780°C.

[0025] After adding Sn, mix well and let it stand for 5 to 10 minutes.

[0026] In step 2), a slag remover is added before the melt enters the serpentine runner and kept warm for 3 to 6 minutes; the slag remover in step 2) is prepared by mixing commercially available YT-J-1 refining agent and YT-D-4 refining agent in a mass ratio of 1:1.

[0027] The casting temperature in step 2) is 700-750°C, and the preheating temperature of the mold is 190-250°C.

[0028] The number of internal arc bends of the serpentine runner is 2 to 4, and the inner diameter of the channel is 8 to 12 mm.

[0029] The temperature of the homogenization annealing treatment in step 3) is 555-570° C., and the homogenization annealing treatment time is 7-10 hours.

[0030] The hot rolling conditions in step 3) are as follows: a temperature of 455-480° C., a reduction of 60-70%, and a reduction of 5-15% per rolling pass. The total reduction after cold rolling is 80-90%. The number of cold rolling passes is ≥2, with a reduction of 1-15% per pass.

[0031] The solid solution conditions in step 4) are: temperature of 510-535° C., and holding time of 20-40 min.

[0032] The cooling refers to cooling with room temperature water.

[0033] Step 4) The natural aging conditions are: temperature of 20-25° C. and time of 6-14 days.

[0034] Step 4) The artificial aging conditions are: temperature of 175-185° C. and time of 0.4-2 h.

[0035] Principle of the present invention:

[0036] Adding Cr to aluminum alloys can control the grain structure. For example, adding Cr to Al-Mg alloys can prevent grain growth. Adding Cr to Al-Mg-Si and Al-Mg-Zn alloys can hinder grain growth during heat treatment. Furthermore, Cr in aluminum alloys can reduce stress corrosion sensitivity and improve the strength and toughness of the material. When added to 6xxx aluminum alloys, Cr can replace Fe in the alloy to form a multi-element phase. For example, Cr replaces part of the Fe in the β-AlFeSi phase to form the β-AlFeMnSi phase. This replacement improves the formation and growth of the β phase, transforming the original needle-shaped β phase into the massive and lumpy α phase. This improves the alloy's performance and suppresses the harmful effects of Fe.

[0037] Sn has a stronger binding ability with vacancies than Mg / Si atoms, so it can capture quenching vacancies during natural aging and hinder the diffusion of Mg / Si atoms, thereby inhibiting the clustering process of natural aging and reducing the negative impact of natural aging on subsequent artificial aging.

[0038] A large number of primary crystal nuclei are generated through the chilled nucleation and heterogeneous nucleation on the inner wall of the serpentine channel. The primary crystal nuclei on the inner wall of the channel are freed and enter the alloy melt under the subsequent flushing action of the alloy melt, realizing the continuous proliferation of the crystal nuclei. At the same time, the alloy melt flows in the serpentine channel and produces "self-stirring". The "self-stirring effect" of the melt not only accelerates the heat exchange between the alloy melt and the inner wall of the channel, but also accelerates the mutual mixing of the alloy melt near the inner wall of the channel and the alloy melt in the center of the channel. The overall temperature of the alloy melt continues to drop rapidly, so that more primary crystal nuclei in the alloy melt are retained. The temperature field and concentration field of the alloy melt at the outlet section at the bottom end of the serpentine channel tend to be uniform, which promotes the ripening and spheroidization of the primary grains and inhibits the growth of dendrites.

[0039] The 6016 recycled aluminum structure and performance control technology of the present invention has the following advantages and beneficial effects:

[0040] (1) The present invention can not only significantly modify and refine the Fe-rich phase in the deformed aluminum alloy, but also improve the aging response speed and aging strengthening effect. Even if the aging time is short, the strength can be significantly improved.

[0041] (2) The aging strengthening effect of the deformed aluminum alloy prepared by the present invention is outstanding, with excellent yield strength and elongation. The yield strength can reach up to 265 MPa, and the elongation is kept very high (~25%).

[0042] (3) The performance of the regenerated Fe-rich 6016 alloy treated by the present invention is even higher than that of the original low-Fe 6016 alloy, showing an excellent Fe impurity tolerance (0.5% to 0.6%), which is conducive to remelting and regeneration.

[0043] (4) The preparation process of the present invention is relatively simple, the operation is simple, the energy consumption and production cost are low, and during smelting, only alloying adjustment needs to be added during the alloy smelting process, without changing the existing mature and stable production line. It is also suitable for the production and application of recycled remelted 6xxx series automotive aluminum alloy plates. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is the SEM microstructure of the 6016 aluminum alloy prepared by ordinary metal mold casting in Comparative Example 1;

[0045] Figure 2 : is the SEM microstructure of the 6016 aluminum alloy prepared in Example 1;

[0046] Figure 3 : is the SEM microstructure image of the 6016 aluminum alloy prepared in Example 2;

[0047] Figure 4 : is the SEM microstructure of the 6016 aluminum alloy prepared in Example 3;

[0048] Figure 5 Schematic diagram of the relationship between hardness and aging time for Comparative Example 1, Example 1, Example 2, and Example 3;

[0049] Figure 6 The yield strength changes of the alloys in various aging states in Comparative Example 1, Example 1, Example 2 and Example 3 are shown. DETAILED DESCRIPTION

[0050] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0051] In order to better illustrate the implementation effect of the present invention, the preparation process flow of producing 6016 deformed aluminum alloy in actual production is taken as Comparative Example 1.

[0052] Comparative Example 1

[0053] 6016 aluminum alloy is a common deformed aluminum alloy used in automobiles. Its preparation process includes alloy smelting, billet casting, homogenization annealing, high-temperature hot rolling, solution water cooling, and artificial aging.

[0054] The final product 6016 alloy in this comparative example has a composition of 0.5% Mg, 1.2% Si, 0.6% Fe, with the remainder being Al and other unavoidable impurities. The basic preparation process and process parameters are as follows:

[0055] 1) Remelt the 6016 aluminum alloy plate and add Al-20Fe master alloy, with the Fe content in the product being 0.6% by mass. The product is melted at 750°C and cast into a steel mold preheated at 200°C to obtain a plate-shaped ingot.

[0056] 2) Perform homogenization annealing on the ingot at a holding temperature of 560°C for 8 hours and then cool it to room temperature.

[0057] 3) The homogenized annealed ingot is heated to 460°C and hot rolled to a plate thickness of 8 mm in multiple passes, with the reduction amount controlled at 10% each time and the total reduction amount being 60%; and then cold rolled to a plate thickness of 2 mm in multiple passes, with a total rolling deformation of 90%.

[0058] 4) The rolled plate was subjected to solid solution treatment at a solid solution temperature of 520°C and a holding time of 30 min; the sample was taken out and placed in room temperature water for rapid cooling to obtain a supersaturated solid solution.

[0059] 5) The supersaturated solid solution is naturally aged at room temperature for 7 days, and then artificially aged at a temperature of 180°C for a time of 0 to 36 hours.

[0060] To characterize the microstructure and mechanical properties of the alloys, a thermal field emission scanning electron microscope was used to observe their microstructure. Mechanical properties were measured using an electronic universal material testing machine, yield strength, yield strength, and elongation at break. The hardness of the alloys was measured using a micro-Vickers hardness tester.

[0061] Mechanical properties test:

[0062] The test samples were machined into dumbbell shapes using wire cutting, and the upper and lower surfaces were polished with 400-grit sandpaper to eliminate the effects of defects on the experimental results. Each set of alloys was tested three times at a tensile speed of 1 mm / min and room temperature (25°C). The stress-strain curves were recorded, and the performance data were obtained, with the average value used as the final test data.

[0063] The gauge length of the specimen is 25 mm, and the elongation δ is calculated according to the following formula:

[0064]

[0065] Where δ is the elongation, %; l0 is the gauge length of the specimen, mm; l1 is the length of the gauge part of the specimen after fracture, mm.

[0066] Figure 1 This is a SEM microstructure image of the as-cast 6016 aluminum alloy prepared in Comparative Example 1. The Fe-rich phase in the untreated 0.6% Fe-content 6016 aluminum alloy is primarily composed of coarse, needle-like β-Fe phases. These coarse, needle-like / plate-like β-Fe phases are potential sites for crack initiation and are most detrimental to tensile properties and ductility.

[0067] The yield strength, tensile strength and elongation of the 6016 aluminum alloy prepared by ordinary metal mold casting in Comparative Example 1 were tested. During peak aging, its yield strength was 201.4 MPa, tensile strength was 258.2 MPa, and elongation was 20.6%; the yield strength increment after 30 minutes of artificial aging was 11.6 MPa.

[0068] To further illustrate the implementation effect of the present invention, the present invention is described below in conjunction with embodiments.

[0069] Example 1

[0070] The alloy used in this example is 6016 alloy. The alloy melting, casting, homogenization annealing, hot rolling, and solutionizing process parameters are the same as those in Comparative Example 1. The difference from Comparative Example 1 lies in the specific alloy composition and the introduction of serpentine channel preparation technology during the casting process. The recycled 6016 aluminum alloy produced in this example contains the following composition: 0.5% Mg, 1.2% Si, 0.6% Fe, 0.1% Cr, 0.08% Sn, with the balance being Al and other unavoidable impurities.

[0071] The processing method of the high-Fe content 6016 aluminum alloy in this embodiment specifically includes the following steps:

[0072] Step 1: Alloy melting to produce Fe-rich recycled 6016 aluminum alloy

[0073] 1.1) Remelt the 6016 aluminum alloy plate and add an Al-20Fe master alloy, where the Fe content in the product is 0.6% by mass. The melting temperature is 750°C. After the alloy is completely melted, stir for 2-10 minutes to homogenize the composition to obtain an aluminum alloy melt, which is then allowed to stand and heat for 5-20 minutes. This step simulates the regeneration of 6016 aluminum alloy, i.e., 6016 aluminum alloy with a high Fe content.

[0074] Step 2: Melt alloying treatment:

[0075] 2.1) Add Al-20Cr master alloy to aluminum melt, with a Cr content of 0.1% by mass in the product, stir, and let stand for 5 minutes;

[0076] 2.2) Adding Sn and Al-10Mg master alloy, with the mass content of Sn in the product being 0.08%, and Mg being supplemented at 15% burn-off (referring to 15% of the 0.5% Mg in the recycled aluminum alloy), stirring and standing for 5 minutes;

[0077] Step 3: Serpentine runner preparation

[0078] 3.1) Add a slag remover before casting. The slag remover is made by mixing the commercially available YT-J-1 refining agent and YT-D-4 refining agent in a mass ratio of 1:1.

[0079] 3.2) Casting at 750°C, the melt first passes through a serpentine channel (the serpentine channel has three bends and the channel inner diameter is 10 mm), then enters a steel mold preheated to 200°C, and is finally cast into an ingot.

[0080] Step 4: Ingot homogenization annealing and rolling forming:

[0081] 4.1) Perform a high-temperature, long-term homogenization annealing on the ingot at 560°C for 8 hours, then cool it to room temperature to allow the alloy components to fully diffuse;

[0082] 4.2) Homogenization annealing The ingot is heated to 460°C and hot rolled in multiple passes to a thickness of 8 mm, with a reduction of 10% each time, and a total reduction of 60%. It is then cold rolled in multiple passes to a thickness of 2 mm, with a total rolling deformation of 90%.

[0083] Step 5: Solution treatment and artificial aging annealing of rolled plates:

[0084] 5.1) The plate was subjected to high-temperature solution treatment at 520°C for 30 min, and then rapidly cooled in room temperature water to obtain a supersaturated solid solution;

[0085] 5.2) The supersaturated solid solution is naturally aged at room temperature for 7 days and then artificially aged at 180°C for 0 to 36 hours.

[0086] Figure 2 This is the SEM microstructure of the as-cast 6016 aluminum alloy prepared in Example 1. After the addition of 0.1Cr, part of the Fe-rich phase in the 6016 aluminum alloy transforms from a coarse needle-like β-Fe phase to a fishbone-like α-Fe phase. However, the control effect of the Fe-rich phase is insufficient, and the needle-like β-Fe phase still exists.

[0087] The alloy's mechanical properties were also tested. At peak aging, its yield strength was 234.7 MPa, its tensile strength was 265.7 MPa, and its elongation was 22.3%. After 30 minutes of artificial aging, the yield strength increased by 16.7 MPa. Compared to Comparative Example 1, the yield strength increased by 33.3 MPa at peak aging.

[0088] Example 2

[0089] The alloy used in this example is 6016 alloy. The alloy melting, casting, homogenization annealing, hot rolling, and solutionizing process parameters are the same as in Example 1. The difference from Example 1 lies in the specific composition of the alloy. The recycled 6016 aluminum alloy produced in this example contains the following composition: 0.5% Mg, 1.2% Si, 0.6% Fe, 0.2% Cr, 0.1% Sn, with the balance being Al and minor amounts of other impurities.

[0090] The method for processing the high-Fe content 6016 aluminum alloy in this embodiment specifically includes the following steps:

[0091] Step 1: Alloy melting to produce Fe-rich recycled 6016 aluminum alloy

[0092] 1.1) Remelt the 6016 aluminum alloy plate and add an Al-20Fe master alloy with an Fe content of 0.6% and a melting temperature of 750°C. After the alloy is completely melted, stir for 2-10 minutes to homogenize the composition to obtain an aluminum alloy melt, which is then allowed to stand and heat for 5-20 minutes.

[0093] Step 2: Melt alloying treatment:

[0094] 2.1) Add Al-20Cr master alloy to aluminum melt, with Cr content of 0.2% by mass in the product, stir, and let stand for 5 minutes;

[0095] 2.2) Adding Sn element and Al-10Mg master alloy, wherein the mass content of Sn in the product is 0.1% and Mg is supplemented according to 15% of the burn-off amount, stirring and standing for 5 minutes.

[0096] Step 3: Serpentine runner preparation

[0097] 3.1) Add a slag remover before casting. The slag remover is made by mixing the commercially available YT-J-1 refining agent and YT-D-4 refining agent in a mass ratio of 1:1.

[0098] 3.2) Casting at 750°C, the melt first passes through a serpentine channel (the serpentine channel has three bends and the channel inner diameter is 10 mm), then enters a steel mold preheated to 200°C, and is finally cast into an ingot.

[0099] Step 4: Ingot homogenization annealing and rolling forming:

[0100] 4.1) Perform a high-temperature, long-term homogenization annealing on the ingot at 560°C for 8 hours, then cool it to room temperature to allow the alloy components to fully diffuse;

[0101] 4.2) Homogenization annealing The ingot is heated to 460°C and hot rolled in multiple passes to a plate thickness of 8 mm, with a reduction of 10% each time, for a total reduction of 60%. It is then cold rolled in multiple passes to a plate thickness of 2 mm, with a total rolling deformation of 90%.

[0102] Step 5: Solution treatment and artificial aging annealing of rolled plates:

[0103] 5.1) The plate was subjected to high-temperature solution treatment at 520°C for 30 min, and then rapidly cooled in room temperature water to obtain a supersaturated solid solution;

[0104] 5.2) The supersaturated solid solution is naturally aged at room temperature for 7 days and then artificially aged at 180°C for 0 to 36 hours.

[0105] Figure 3This is a SEM microstructure image of the as-cast 6016 aluminum alloy prepared in Example 2. The addition of 0.2Cr transforms most of the Fe-rich phase in the 6016 aluminum alloy from the coarse, needle-like β-Fe phase to the fishbone-like α-Fe phase, significantly regulating the Fe-rich phase. However, the fishbone-like α-Fe phase is large in size and difficult to break into thin rod-like Fe phases during subsequent rolling, resulting in insufficient alloy strengthening.

[0106] Similar to Comparative Example 1, the yield strength, tensile strength, and elongation of the 6016 aluminum alloy prepared by conventional mold casting in Example 1 were tested. At peak aging, the yield strength was 250.1 MPa, the tensile strength was 282.2 MPa, and the elongation was 20.3%. After 30 minutes of artificial aging, the yield strength increased by 21 MPa. Compared to Comparative Example 1, the yield strength increased by 48.7 MPa at peak aging. It can be seen that after the Cr-Sn composite microalloying treatment, the yield strength of the alloy at all stages was significantly improved. The increase after 30 minutes of artificial aging also increased, and the elongation after aging remained above 20%.

[0107] Example 3

[0108] The alloy used in this example was 6016 alloy. The alloy melting, casting, homogenization annealing, hot rolling, and solutionizing process parameters were the same as in Example 2, differing from Example 2 in the casting temperature during the serpentine channel preparation. The recycled 6016 aluminum alloy produced in this example contained the following composition: 0.5% Mg, 1.2% Si, 0.6% Fe, 0.1% Cr, 0.11% Sn, with the balance being Al and a small amount of other unavoidable impurities.

[0109] The method for processing the high-Fe content 6016 aluminum alloy in this embodiment specifically includes the following steps:

[0110] Step 1: Alloy melting to produce Fe-rich recycled 6016 aluminum alloy

[0111] 1.1) Remelt the 6016 aluminum alloy plate and add an Al-20Fe master alloy with an Fe content of 0.6% and a melting temperature of 750°C. After the alloy is completely melted, stir for 2-10 minutes to homogenize the composition to obtain an aluminum alloy melt, which is then allowed to stand and heat for 5-20 minutes.

[0112] Step 2: Melt alloying treatment:

[0113] 2.1) Add Al-20Cr master alloy to aluminum melt, with Cr content of 0.2% by mass in the product, stir, and let stand for 5 minutes;

[0114] 2.2) Adding Sn element and Mg-containing master alloy, wherein the mass content of Sn in the product is 0.11% and Mg is supplemented according to 15% of the burn-off amount, stirring and standing for 5 minutes.

[0115] Step 3: Serpentine runner preparation

[0116] 3.1) Add a slag remover before casting. The slag remover is made by mixing the commercially available YT-J-1 refining agent and YT-D-4 refining agent in a mass ratio of 1:1.

[0117] 3.2) Casting at 700°C, the melt first passes through a serpentine channel (the serpentine channel has three bends and the channel inner diameter is 10 mm), then enters a steel mold preheated to 200°C, and is finally cast into an ingot.

[0118] Step 4: Ingot homogenization annealing and rolling forming:

[0119] 4.1) Perform a high-temperature, long-term homogenization annealing on the ingot at 560°C for 8 hours, then cool it to room temperature to allow the alloy components to fully diffuse;

[0120] 4.2) Homogenization annealing The ingot is heated to 460°C and hot rolled in multiple passes to a plate thickness of 8 mm, with a reduction of 10% each time, for a total reduction of 60%. It is then cold rolled in multiple passes to a plate thickness of 2 mm, with a total rolling deformation of 90%.

[0121] Step 5: Solution treatment and artificial aging annealing of rolled plates:

[0122] 5.1) The plate was subjected to high-temperature solution treatment at 520°C for 30 min, and then rapidly cooled in room temperature water to obtain a supersaturated solid solution;

[0123] 5.2) The supersaturated solid solution is naturally aged at room temperature for 7 days and then artificially aged at 180°C for 0 to 36 hours.

[0124] Figure 4 This is a SEM microstructure image of the as-cast 6016 aluminum alloy prepared in Example 3. Similar to Example 1, Cr replaces some Fe atoms in the Fe-rich phase, transforming the majority of the Fe-rich phase from a coarse, needle-like β-Fe phase to a fishbone-like α-Fe phase. Furthermore, the serpentine channel casting technique, performed at 700°C, results in a smaller Fe-rich phase and a more pronounced refinement.

[0125] Figure 5 3 is a graph showing the relationship between hardness and aging time for Comparative Example 1, Example 1, Example 2, and Example 3; the peak aging time of the four groups of samples is close, the peak aging hardness of Comparative Example 1 is the lowest at 88 HV, and the peak aging hardness of Examples 1 and 3 is the highest, reaching 99 HV.

[0126] Figure 6 The yield strength changes of the alloys in various aging states for Comparative Example 1, Example 1, Example 2, and Example 3 are shown. The yield strength of Example 3 at each state is higher than that of the other groups. At peak aging, its yield strength is 265.2 MPa, its tensile strength is 308.7 MPa, and its elongation is 23.8%. After 30 minutes of artificial aging, the yield strength increase is 19 MPa. Compared with Comparative Example 1, the yield strength is increased by 63.8 MPa.

[0127] To better illustrate the differences in the processes and effects between Comparative Example 1 and Examples 1-3, the performance data are summarized in Table 1. In Example 3 of the present invention, after subjecting the melt to Cr / Sn microalloying, the alloy's microstructure and properties were manipulated using a serpentine channel preparation technique. This process effectively refines the primary α-Al grains in the 6016 recycled alloy, improving roundness and effectively transforming the Fe-rich phase from a coarse, long needle-like shape to a fine, Chinese character-like shape. The overall performance of Example 3 is superior. Compared to the high-Fe 6016 aluminum alloy prepared by conventional mold casting in Comparative Example 1, Example 3 achieves improved aging response while simultaneously controlling the Fe-rich phase.

[0128] Table 1 Performance parameters of alloys prepared in Comparative Example 1 and Examples 1 to 3

[0129]

[0130] Based on the above examples, the key to the composite treatment method of the present invention lies in the Cr-Sn composite microalloying treatment and the coordinated serpentine channel preparation technology, which effectively reduces the adverse effects of the impurity element Fe in the recycled aluminum alloy on the mechanical properties, modifies the Fe phase, significantly refines the α-Al grains, and improves the alloy's response to artificial aging. While having a high aging response, the alloy also has excellent ductility and yield strength at all stages of artificial aging.

[0131] In order to more conveniently illustrate the implementation effect of the present invention, the present invention further changes the processing method for alloy preparation, processes 6016 aluminum alloy, and provides comparative illustrations.

[0132] Comparative Example 2

[0133] In this comparative example, a low-Fe content virgin 6016 alloy was selected, containing the following composition: 0.5% Mg, 1.2% Si, 0.15% Fe, with the remainder being Al and other unavoidable impurities. The basic preparation process and process parameters were the same as those of Comparative Example 1.

[0134] In step 1), the original 6016 aluminum alloy plate is remelted at a melting temperature of 750° C. and cast into a steel mold preheated at 200° C. to obtain a plate-shaped ingot. Other preparation steps and parameters are the same as those in Comparative Example 1.

[0135] Similarly, the mechanical properties of the alloy were tested. The yield strength of the alloy in the supersaturated solid solution state was 91.2 MPa, the yield strength after painting was 102.5 MPa, the yield strength of the alloy in the peak-aged state was 253.1 MPa, and the peak-aged elongation was 32.2. Compared with Comparative Example 1, the alloy's yield strength was improved due to the lower Fe content, while also exhibiting a higher elongation. However, the strength gain after painting was still low. All mechanical properties of the present invention were superior to those of the native 6016 aluminum alloy in Comparative Example 2.

[0136] Comparative Example 3

[0137] The 6016 alloy produced in this comparative example contains the following composition: 0.5% Mg, 1.2% Si, 0.6% Fe, 0.1% Sn, 0.2% Cr, with the balance being Al and other impurities. Except for not using a serpentine runner, the other steps and parameters in this comparative example are the same as those in Example 1.

[0138] Similarly, the mechanical properties of the alloy were tested. The influence of aging time on the hardness of the alloy is similar to that obtained in Example 1. Compared with Comparative Example 1, the hardness increment is significantly improved after 30 minutes of artificial aging. The yield strength of the alloy in the supersaturated solid solution state is 95.4MPa, the yield strength after baking paint is 117.8Mpa, and the yield strength of the alloy in the peak aging state is 196.4MPa. Compared with Example 3, the yield strength in each state is lower. It was also found from the microstructure that although the Fe-rich phase has been deteriorated, the size of the Fe phase is relatively large. This shows that although the treatment of the alloy by microalloying alone can transform most of the Fe-rich phase from a coarse needle-shaped β-Fe phase to a fishbone-shaped α-Fe phase, the refinement effect on the Fe phase is insufficient, which is not conducive to subsequent rolling and crushing. Therefore, the performance parameters of Comparative Example 3, which only performs Cr / Sn microalloying, are not as good as those of the present invention.

[0139] Comparative Example 4

[0140] The 6016 alloy produced in this comparative example contains the following composition: 0.5% Mg, 1.2% Si, 0.6% Fe, with the balance being Al and other impurities. The alloy was cast using a serpentine channel process at 700°C. Microalloying was not performed in this comparative example; the other basic preparation procedures and process parameters were consistent with those in Example 1.

[0141] Similarly, the mechanical properties of the alloy were tested. The influence of aging time on the hardness of the alloy is similar to that obtained in Example 3. The yield strength of the alloy in the supersaturated solid solution state is 90.2MPa, the strength after baking paint is 103.8, and the yield strength of the alloy in the peak aging state is 223.9MPa. Compared with Example 1, the strength of each stage of artificial aging is lower, and the strength increment after 30 minutes of artificial aging is lower. It was found in the microstructure that the morphology of the Fe-rich phase is still needle-shaped. This shows that the introduction of only the serpentine channel preparation technology cannot achieve effective modification of the Fe phase, and has no significant effect on aging precipitation. It is necessary to combine Cr / Sn microalloying with the serpentine channel preparation technology to effectively modify the Fe phase, significantly refine the α-Al grains, and improve the responsiveness of the alloy to artificial aging. Therefore, the performance parameters of Comparative Example 4, which only adds the serpentine channel preparation technology, are not as good as those of the present invention.

[0142] The implementation methods of the present invention are not limited to the embodiments described. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for regulating the microstructure and properties of high-Fe content 6016 recycled aluminum alloy, characterized by: The following steps are involved: 1) Microalloying treatment: melt the 6016 aluminum alloy with high Fe content, add the Cr-containing master alloy, mix well, let it stand, and then add Sn to obtain a microalloyed melt; 2) Preparation using a serpentine runner: The melt passes through the serpentine runner and then enters the mold to be cast into an ingot; 3) The ingot is subjected to homogenization annealing treatment, air-cooled after hot rolling, and then cold-rolled to obtain a plate; 4) subjecting the plate to high-temperature solid solution and cooling to obtain a supersaturated solid solution; subjecting the supersaturated solid solution to natural aging and artificial aging treatment to obtain a deformed aluminum alloy, i.e., a recycled aluminum alloy; The product deformed aluminum alloy contains the following components by mass: Mg: 0.45-0.6%; Si: 1.0-1.2%; Fe: 0.2%~0.6%; Cr：0.1～0.3％； Sn: 0.08~0.15%.

2. The method for regulating the microstructure and properties of high-Fe content 6016 recycled aluminum alloy according to claim 1, characterized in that: The Cr content is 0.15-0.3%; the Sn content is 0.1-0.15%; the balance in the product deformed aluminum alloy is Al or Al and other impurities; The casting temperature in step 2) is 700-750°C.

3. The method for regulating the microstructure and properties of high-Fe content 6016 recycled aluminum alloy according to claim 1, characterized in that: In step 2), the preheating temperature of the mold is 190-250° C.; The number of internal arc bends of the serpentine runner is 2 to 4, and the inner diameter of the channel is 8 to 12 mm.

4. The method for regulating the microstructure and properties of high-Fe content 6016 recycled aluminum alloy according to claim 1, characterized in that: The temperature of the homogenization annealing treatment in step 3) is 555-570° C., and the homogenization annealing treatment time is 7-10 hours; The hot rolling conditions in step 3) are as follows: temperature of 455-480° C., reduction of 60-70%, reduction of 5-15% per rolling pass; total reduction after cold rolling of 80-90%; number of cold rolling passes ≥ 2, reduction of 1-15% per rolling pass.

5. The method for regulating the microstructure and properties of high-Fe content 6016 recycled aluminum alloy according to claim 1, characterized in that: The solid solution conditions in step 4) are: temperature of 510-535° C., holding time of 20-40 min; The cooling refers to cooling with room temperature water; Step 4) The natural aging conditions are: temperature of 20-25°C and time of 6-14 days; Step 4) The artificial aging conditions are: temperature of 175-185° C. and time of 0.4-2 h.

6. The method for regulating the microstructure and properties of high-Fe content 6016 recycled aluminum alloy according to claim 1, characterized in that: In step 1), the microalloyed melt needs to be supplemented with Mg to avoid burnout. Mg is added in the form of an intermediate alloy and is added together with Sn. The Cr-containing master alloy in step 1) is Al-20Cr or Al-10Cr master alloy.

7. The method for regulating the microstructure and properties of high-Fe content 6016 recycled aluminum alloy according to claim 6, characterized in that: The Mg master alloy is the master alloy Al-10Mg; The amount of Mg burned is supplemented by 10 to 20% of the Mg content in the product deformed aluminum alloy.

8. The method for regulating the microstructure and properties of high-Fe content 6016 recycled aluminum alloy according to claim 1, characterized in that: The standing time in step 1) is 4 to 10 minutes; The melting temperature in step 1) is 740°C to 780°C.

9. The method for regulating the microstructure and properties of high-Fe content 6016 recycled aluminum alloy according to claim 1, characterized in that: After adding Sn, mix well and let it stand for 5 to 10 minutes; In step 2), a slag remover is added before the melt enters the serpentine runner and the melt is kept warm for 3 to 6 minutes.

10. Use of a deformed green aluminum alloy obtained by the method according to any one of claims 1 to 9, characterized in that: The deformed aluminum alloy is used in the field of automobile plates.

Images