A method for simultaneously improving the machining performance and thermal conductivity of a recycled high-Fe-content Al-Mg-Si-based aluminum alloy

Abstract

This invention belongs to the technical field of recycled aluminum alloys, and discloses a method for simultaneously improving the machinability and thermal conductivity of recycled high-Fe content Al-Mg-Si based aluminum alloys. The method involves: 1) remelting the recycled high-Fe content Al-Mg-Si based aluminum alloy, microalloying treatment, slag removal, refining, and casting; then high-temperature homogenization annealing, immediately followed by large-deformation hot rolling, rapid quenching, room-temperature rolling, and artificial aging treatment to obtain the final recycled aluminum alloy; the large-deformation hot rolling refers to directly rolling the aluminum alloy sheet with a large deformation of 30-40% after removing it from the homogenization furnace; the total time for the aluminum alloy sheet to be removed from the homogenization furnace, hot rolled, and quenched does not exceed 12 seconds. This method achieves high strength while simultaneously improving the thermal conductivity and machinability of the aluminum alloy, meeting the high-end requirements of new energy vehicle heat sink shells, precision structural components, etc.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloys, and specifically relates to a method for simultaneously improving the machinability and thermal conductivity of recycled high-Fe content Al-Mg-Si based aluminum alloys. Background Technology

[0002] The new energy vehicle and electronic heat dissipation industries have an urgent need for lightweight, cost-effective materials with good overall performance. Recycled high-Fe content Al-Mg-Si aluminum alloys, due to their significant low-carbon advantages, have become a key candidate material for achieving green manufacturing in these fields. Key components such as battery pack lower casings, motor housings, and liquid cooling plates require materials with sufficient mechanical strength and toughness to ensure structural safety, excellent thermal conductivity for efficient thermal management, and good machinability to ensure that complex sealing surfaces and flow channels can be manufactured with high precision and efficiency. Similarly, other key electronic communication fields require materials that balance high thermal conductivity and good machinability, while possessing moderate mechanical properties to ensure structural stability. However, due to the unavoidable high Fe content and compositional fluctuations in waste aluminum raw materials, the above-mentioned properties of recycled aluminum alloys are generally lower than those of virgin alloys, and there are also serious mutual constraints between them, becoming a major bottleneck for the application of recycled aluminum alloys in key electronic communication fields. Specifically, this manifests in the following aspects: (1) The inverse relationship between mechanical properties and thermal conductivity: The alloying elements that enhance strength and the coarse second phases formed (such as needle-like β-Fe phase) introduce lattice distortion and interfaces, hindering the transmission of electrons and phonons, and severely sacrificing the thermal and electrical conductivity of the material. (2) The contradiction between mechanical properties and machinability: The heat treatment carried out to compensate for the loss of strength introduces a strengthening phase, but also increases the hardness of the matrix, resulting in increased cutting force, accelerated tool wear, and difficulty in chip breaking, directly damaging processing efficiency and surface quality. (3) The contradiction between performance stability and cost control: Fluctuations in raw material composition directly lead to poor stability of the final product in terms of mechanical, thermal conductivity, and processing performance. The fine pretreatment and complex process control required to achieve performance stability will significantly increase production costs and weaken its economic advantages.

[0003] Chinese invention patent application No. 202510060310.0 discloses a high-strength free-machining aluminum alloy material and its preparation process. This patent application uses the addition of trace amounts of metallic Ba (0.05-0.15%) to suppress coarse AlSi phase microstructure, combined with staged heating solution treatment and aging treatment at 175℃ for 6 hours. However, the main raw materials are added in the form of alloying element powder, which is difficult to control and poses safety risks. Furthermore, the staged heating process requires strict temperature control, resulting in high equipment costs. In pursuing high machinability, other process adaptability may be sacrificed, and there is still room for optimization in terms of overall performance balance. Chinese invention patent application No. 202010215729.6 discloses a high-strength, heat-resistant, lead-free free-machining aluminum alloy and its preparation method. This patent targets high-strength wrought aluminum alloys (AL-Zn-Mg-Cu) as raw materials. It involves replacing toxic Pb with a composite of Sn (0.65~0.75%) and Bi (0.15~0.25%), and adding various microalloying elements such as Zr, V, Nd, and Yb for synergistic strengthening. The process then includes atomization powdering, hot pressing, cladding hot extrusion, and solution aging. However, the preparation process involves rapid solidification and powder metallurgy technology, making it complex and costly to manufacture, posing challenges to the economic viability and efficiency of large-scale production.

[0004] Chinese invention patent application No. 202211701401.0 discloses a recycled high thermal conductivity die-cast aluminum alloy containing rare earth elements and its preparation method. The Si content is 9.0%–12.0%, belonging to a typical near-eutectic cast aluminum alloy. This patent application uses recycled waste aluminum as raw material, adds a specific ratio of rare earth elements, optimizes the basic alloy composition, and combines a preparation process of "raw material pretreatment for impurity removal → rare earth microalloying → vacuum melting → die casting → low-temperature aging." The resulting aluminum alloy achieves efficient recycling of waste aluminum resources while possessing excellent thermal conductivity and good die-casting adaptability. However, its raw material pretreatment requirements are strict, production consistency is difficult to control, and its performance is prone to degradation in environments above 200℃, with limited high-temperature stability and unclear machinability.

[0005] The aforementioned literature either involves complex processes or high-cost equipment, or some performance aspects do not meet the requirements of high-precision products, or fail to achieve a good overall effect in terms of mechanical, thermal conductivity, and machinability. Furthermore, there is a lack of corresponding machining and cutting research in the field of recycled aluminum alloys, which currently places high demands on the practical applications of recycled aluminum alloys.

[0006] This invention targets recycled high-Fe content Al-Mg-Si based wrought aluminum alloys. It employs efficient melt treatment technology and efficient heat treatment processes to obtain a preparation process that simultaneously improves the machinability and thermal conductivity of recycled high-Fe content Al-Mg-Si based aluminum alloys. This achieves a balance between the dual objectives of "improving both machinability and thermal conductivity," breaking through the technical bottleneck in the field of recycled aluminum alloys where "performance improvement inevitably increases process complexity." This provides a feasible solution for quality upgrading of high-Fe content Al-Mg-Si based recycled alloys. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, this invention provides a method for simultaneously improving the machinability and thermal conductivity of recycled high-Fe content Al-Mg-Si aluminum alloys. This invention introduces B-Bi / Sn microalloying elements and combines homogenization annealing, short-time hot rolling, and solution quenching into a short-process heat treatment step. Combined with the synergistic control of cold rolling and aging, this significantly refines the precipitated phases in the alloy and promotes their uniform distribution, transforming the Fe-rich phase from needle-like and lamellar to blocky and dispersed. Bi and Sn are almost insoluble in the aluminum matrix and disperse as tiny, independent soft particles. During cutting, these soft particles act as tiny "lubricating points," reducing friction between the tool and chips. More importantly, as stress concentration points, they effectively promote short, easily broken chips, rather than forming long, tangled continuous chips. This enhances the alloy's strengthening effect while effectively mitigating the adverse effects of impurity phases, thereby significantly improving the material's machinability and thermal conductivity. Bi and Sn atoms may adsorb onto the growth interface of the Fe-rich phase, altering its surface energy and thus inhibiting rapid growth along a specific direction, causing it to grow in an isotropic manner. This invention optimizes the heat treatment process in industrial production, facilitating the manufacturing of high-strength, high-conductivity, and easily recyclable wrought aluminum alloy profiles.

[0008] To achieve the above objectives, the present invention adopts the following technical solution;

[0009] A method for simultaneously improving the machinability and thermal conductivity of recycled high-Fe content Al-Mg-Si based aluminum alloys includes the following steps:

[0010] 1) Remelting a recycled high-Fe content Al-Mg-Si based aluminum alloy yields a recycled aluminum alloy melt. The recycled high-Fe content Al-Mg-Si based aluminum alloy consists of the following components by mass percentage: Si 0.65%~0.75%, Fe 0.85%~1.05%, Mg 0.75%~0.85%, Cu 0.32%~0.42%, Mn 0.25%~0.35%, Cr 0.15%~0.25%, Zn 0.35%~0.45%, Ni 0.15%~0.25%, Ti 0.25%~0.35%, V 0.15%~0.25%, Pb 0.35%~0.45%, Zr 0.15%~0.25%; the total mass of unavoidable impurities is ≤0.5wt.%, with the balance being Al.

[0011] 2) Add a boron-containing master alloy and an R metal, or a boron-containing master alloy and a Ce-containing master alloy, to the recycled aluminum alloy melt, and perform microalloying treatment at 735℃~775℃; the R metal is Bi and / or Sn; the amount of B added is 0.04%~0.06% of the mass of the final product aluminum alloy; when the R metal is Bi and / or Sn, the amount of Bi added is 0.55%~0.65% of the mass of the final product aluminum alloy, and the amount of Sn added is 0.25%~0.35% of the mass of the final product aluminum alloy; the microalloying refers to holding at 735℃~775℃ for 15~40 minutes; the amount of Ce added is 0.14%~0.16% of the mass of the final product aluminum alloy.

[0012] 3) Remove slag from the melt obtained in step (2), refine it, and cast it to obtain recycled deformed aluminum alloy sheet.

[0013] 4) The recycled deformed aluminum alloy sheet from step 3) is subjected to high-temperature homogenization annealing, and then immediately subjected to large deformation hot rolling and rapid quenching to obtain the rolled and quenched sheet.

[0014] 5) The sheet material from step 4) is rolled at room temperature and artificially aged to obtain the final recycled aluminum alloy.

[0015] The remelting temperature mentioned in step 1) is 730-785℃, and the remelting time is 1.5~2.5h.

[0016] Step 2) The B master alloy, Bi, and Sn are respectively Al-3B master alloy, Bi particles with a purity of 99.5% and Sn particles with a purity of 99.5%.

[0017] In step 2), the temperature for microalloying treatment is 735~755℃; the holding time is 20~30min.

[0018] Step 3) involves the following steps: adding a slag remover to the melt, stirring until homogeneous, allowing it to stand, removing the slag, and then refining it by introducing argon gas. After refining, the slag is removed and the melt is allowed to stand. Subsequently, the melt is cast into a preheated mold to obtain a recycled deformed aluminum alloy sheet.

[0019] The slag removal agent is made by mixing commercially available YT-J-1 refining agent and YT-D-4 refining agent in a mass ratio of 1:1; the refining refers to the introduction of 99.99% high-purity argon gas for 3 to 9 minutes; the slag removal and settling time after refining is 3 to 9 minutes.

[0020] The mass ratio of the slag remover to the melt is (0.5~1.5):99. Argon gas is introduced for 5~7 minutes; the slag removal and settling time is 5~7 minutes.

[0021] The preheating temperature of the mold is 185-285℃, and the temperature of the melt during casting is 715℃~735℃.

[0022] The homogenization annealing temperature in step 4) is 525~565℃, and the annealing time is 6.5~12.5h. Preferably, the homogenization annealing temperature is 535~545℃, and the annealing time is 7.5~8.5h.

[0023] Step 4) describes large deformation hot rolling, which refers to directly rolling a 30-40% large deformation aluminum alloy sheet after uniform annealing from the furnace. Quenching refers to quenching the hot-rolled sheet in water at room temperature (23-33°C). Preferably, the time for the recycled aluminum alloy sheet to be removed from the homogenization furnace, hot-rolled, and quenched does not exceed 12 seconds. The hot rolling time is 3-5 seconds. The quenching time is 2-6 seconds.

[0024] Step 5) describes room temperature rolling in 5-7 passes, with a total rolling weight of 60-67%, and each pass compressing the same volume or height. Preferably, each pass deforms 10-20%. More preferably, the number of passes is 6, with each pass compressing the same height.

[0025] The temperature for artificial aging in step 5) is 185℃~235℃ and the aging time is 0.1~30h. Preferably, the temperature for artificial aging is 215~235℃ and the aging time is 0.5~4h.

[0026] This invention achieves synergistic optimization of cutting performance and thermal conductivity through the technical route of "composite micro-alloying-homogenization hot rolling quenching short-process heat treatment". The principle is as follows: (1) Ternary composite modification mechanism: Dual modification of element B: 0.05% B atoms are adsorbed at the Fe phase nucleation interface, inducing the transformation of β-Fe phase to spherical α-Fe phase with a conversion rate ≥90%, reducing the average size of Fe phase. This morphological transformation reduces cutting force and tool wear. Bi-Sn low melting point lubricating phase: 0.6% Bi and 0.3% Sn form a eutectic phase, which softens under the action of cutting heat, reducing the friction coefficient to 0.15, and the chips change from continuous band to short fragments (length <8mm). Synergistic enhancement of elements: Sn and Mg form Mg2Sn heterogeneous nucleation core, which increases the density of the strengthening phase (Mg2Si) by 30%, while Bi inhibits the aggregation of Sn phase, avoiding the imbalance between strength and machinability. (2) Homogenization hot rolling and quenching short-process heat treatment: Homogenization → large deformation hot rolling → rapid quenching integrated process, utilizing residual heat to break down the residual Fe phase to the submicron level, while increasing the supersaturated solid solution formation rate, laying the foundation for age hardening. Deformation introduces a high dislocation density, and the two work together to promote the uniform precipitation of the β'' phase along the dislocation line, narrowing the size distribution of the precipitated phase and reducing the obstruction to the cutting process.

[0027] The recycled aluminum alloys processed by this technology exhibit excellent machinability: chip length ≤10mm, meeting relevant processing standards. Cost advantages: No need to add precious elements such as Mo and Zr, reducing the production cost per ton of alloy while simultaneously unlocking the potential for high-quality utilization of scrap aluminum.

[0028] The recycled aluminum alloy of this invention meets the high-end requirements of new energy vehicle heat dissipation shells, precision structural parts, etc.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] (1) The method of this invention is specifically designed for processing recycled aluminum with high Fe impurity content. Through improvements in composite microalloying and heat treatment processes, the prepared recycled wrought aluminum alloys possess high thermal conductivity, high strength, and easy machinability. This provides a reliable technical solution for the large-scale production of low-cost, high-performance recycled wrought aluminum alloys.

[0031] (2) The traditional three independent processes of homogenization annealing, hot rolling and solution quenching are combined into one continuous step, which shortens the traditional production cycle by 14 hours. This design reduces the energy consumption of repeated heating and cooling, improves production efficiency, meets the requirements of green manufacturing, and reduces the production cost of enterprises.

[0032] (3) This invention employs an appropriate amount of Bi / Sn and a composite microalloying strategy to replace toxic Pb, and adds additional B element to purify the recycled aluminum alloy melt. This combination not only utilizes Bi / Sn to form soft particles to significantly improve the machinability of the material, but also retains high mechanical and thermal properties through the composite addition of B-Bi / Sn.

[0033] (4) Through a synergistic deformation heat treatment of "high temperature homogenization + direct large deformation hot rolling + quenching + cold rolling + aging", the precipitated phases are significantly refined and uniformly distributed. This regulation achieves high strength while simultaneously improving the thermal conductivity and machinability of the alloy, thus resolving the contradiction between high strength and high thermal conductivity.

[0034] (5) The thermal conductivity of the high Fe content Al-Mg-Si based wrought aluminum alloy processed by this preparation process exceeds 190 W / (m・K), the average chip length is reduced from 65 mm to about 6 mm, the chip shape changes from long spiral chips to C-shaped chips, while maintaining high yield strength, and has excellent comprehensive performance. Attached Figure Description

[0035] Figure 1 The image shows the optical microstructure of the alloy in the as-cast state in Comparative Example 1.

[0036] Figure 2 The image shows the optical microstructure of the alloy in the homogeneous state in Comparative Example 1.

[0037] Figure 3 The chip morphology of the alloy in Comparative Example 1 after heat treatment is shown.

[0038] Figure 4 The chip morphology of the alloy in Comparative Example 2 after heat treatment.

[0039] Figure 5 The chip morphology of the alloy in Comparative Example 3 after heat treatment is shown.

[0040] Figure 6 The chip morphology of the alloy in Example 1 after heat treatment;

[0041] Figure 7 The chip morphology of the alloy in Example 2 after heat treatment;

[0042] Figure 8 The chip morphology of the alloy in Example 3 after heat treatment;

[0043] Figure 9 The image shows the chip morphology of the alloy in Example 4 after heat treatment. Detailed Implementation

[0044] The present invention will be described in further detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0045] Comparative Example 1: Preparation and treatment of recycled high-Fe content Al-Mg-Si based aluminum alloys using traditional heat treatment processes

[0046] The recycled high-Fe content Al-Mg-Si based aluminum alloy of this comparative example contains the following components by mass percentage: Si 0.65%, Fe 0.96%, Mg 0.75%, Cu 0.42%, Mn 0.26%, Cr 0.15%, Zn 0.35%, Ni 0.15%, Ti 0.25%, V 0.15%, Pb 0.36%, Zr 0.17%; unavoidable impurities total ≤0.5wt.%, balance being Al. The processing steps for the recycled high-Fe content Al-Mg-Si based aluminum alloy are alloy melting, homogenization treatment, rolling forming, solution treatment, and artificial aging.

[0047] (1) Alloy smelting

[0048] When the furnace temperature reaches 775℃, add recycled high-Fe content Al-Mg-Si based aluminum alloy and wait for it to melt. When the melt temperature drops to the range of 730~770℃, add an appropriate amount of slag remover (the slag remover is made by mixing commercially available YT-J-1 refining agent and YT-D-4 refining agent in a mass ratio of 1:1), stir evenly, and let it stand. Remove the slag from the surface of the alloy liquid, then pass 99.9% argon gas through it for 6 minutes to refine it. After refining, remove the slag from the surface of the alloy liquid, let it stand for 6 minutes, and then pour the melt at a temperature of 705℃~725℃ into a metal mold with a preheating temperature of 200℃ to cast it into shape, thus obtaining a recycled high-Fe content Al-Mg-Si based aluminum alloy sheet (20mm thick).

[0049] (2) Homogenization treatment

[0050] The recycled high Fe content Al-Mg-Si based aluminum alloy sheet obtained in step (1) was subjected to high temperature and long time homogenization annealing. The homogenization annealing temperature was 540℃ and the homogenization annealing time was 8h. Then the aluminum alloy was cooled in the furnace for 12~18h to room temperature to make the alloy composition uniform.

[0051] (3) Rolling and forming

[0052] The recycled aluminum alloy after homogenization annealing in step (2) is subjected to multiple hot rolling passes to obtain a rolled plate with a thickness of 5 mm. The hot rolling passes are 8, the pressure in each pass is controlled within 20%, the total rolling deformation is 75%, and the hot rolling temperature is 480℃.

[0053] (4) Solution treatment

[0054] The recycled aluminum alloy sheet rolled in step (3) is subjected to solution treatment at a temperature of 540°C for 4 hours. The solution-treated recycled aluminum alloy sheet is then quenched with room temperature cooling water at a temperature of 23-33°C to obtain a supersaturated solid solution.

[0055] (5) Artificial aging treatment

[0056] Artificial aging treatment was carried out on the recycled aluminum alloy sheet that had undergone solution treatment in step (4). The aging temperature was 220℃ and the aging time was up to 30h.

[0057] Figure 1 The image shows the optical microstructure of the alloy in the as-cast state in Comparative Example 1. Figure 2 The image shows the optical microstructure of the alloy in the homogeneous state in Comparative Example 1. As can be seen from the image, the iron-rich phase in the unmodified portion of the alloy is distributed in a needle-like pattern.

[0058] Regenerated high-Fe content Al-Mg-Si based aluminum alloys treated by traditional heat treatment processes have a peak aging thermal conductivity of only 177 W / (m·K), a yield strength of only 256.7 MPa, a long helical cutting shape, an average chip length of 65 mm, and poor machinability; after aging, the thermal conductivity is only 185 W / (m·K).

[0059] Example 1: Preparation and treatment of recycled high-Fe content Al-Mg-Si based wrought aluminum alloys via 0.05B-0.6Bi microalloying and novel deformation heat treatment process.

[0060] In this embodiment, the composition of the recycled high-Fe content Al-Mg-Si based wrought aluminum alloy is the same as that of Comparative Example 1. The processing steps for the recycled high-Fe content Al-Mg-Si based aluminum alloy are alloy melting, B-Bi microalloying, homogenization rolling and quenching short-process heat treatment, cold rolling pre-deformation and artificial aging, which simultaneously improve the machinability and thermal conductivity of the recycled high-Fe content Al-Mg-Si based aluminum alloy.

[0061] Specifically, the following steps are included:

[0062] (1) Alloy smelting and casting:

[0063] When the furnace temperature reaches 775℃, add the recycled aluminum alloy and wait for it to melt. When the melt temperature drops to 745℃, simultaneously add Al-3B master alloy and Bi particles with a purity of 99.5%, so that the melt contains 0.05% B and 0.6% Bi (B content is 0.05% of the final product aluminum alloy mass; Bi content is 0.6% of the final product aluminum alloy mass). After standing for 25 minutes, add a slag remover with a mass ratio of 1:99 to the melt (the slag remover is commercially available). The YT-J-1 refining agent and YT-D-4 refining agent are mixed in a 1:1 mass ratio. After stirring evenly, the mixture is allowed to stand, and the melt temperature is controlled at 735℃~755℃. The slag on the surface of the alloy liquid is removed, and then 99.9% argon gas is introduced for refining for 6 minutes. After refining, the slag on the surface of the alloy liquid is removed, and the mixture is allowed to stand for 6 minutes. The melt at a temperature of 715℃~735℃ is poured into a metal mold with a preheated temperature of 200℃ and cast to obtain recycled high Fe content Al-Mg-Si based aluminum alloy sheet.

[0064] (2) Short-process heat treatment process including diffusion annealing, rolling, and quenching

[0065] Directional heat treatment was performed on as-cast recycled aluminum alloy sheets: First, a high-temperature, long-duration diffusion annealing treatment (i.e., homogenization treatment) was carried out at 540℃ for 8 hours to ensure sufficient diffusion of elements within the alloy. This gradually reduced the interfacial energy of the acicular β-Fe phase, transforming it into the thermodynamically more stable bulk α-Fe phase through atomic reconstruction. Furthermore, the long 8-hour holding time prevented coarsening of the Fe phase during the transformation process, resulting in a reduction in the average size of the bulk Fe phase from the original 10-15 μm to 3-5 μm. After diffusion annealing, the sheet metal is removed from the furnace and immediately subjected to hot rolling with a large deformation of 35% in a single pass. After rolling, it is rapidly immersed in room temperature water (23-33°C) for quenching. During quenching, dislocation recovery and annihilation are suppressed, while the high-density dislocations introduced by hot rolling are retained. This results in an optimized microstructure of "dispersed Fe phase + high-density dislocations + supersaturated solid solution," providing microstructural support for the synergistic improvement of the alloy's machinability and thermal conductivity. The final product is a recycled aluminum alloy sheet with a thickness of approximately 13mm. Throughout the process, the total heat transfer time from removal from the diffusion annealing furnace, hot rolling, to water quenching is strictly controlled to ≤12s. Precise time control and parameter matching ensure both microstructure regulation and dimensional accuracy. The quenching time is 3s, and the hot rolling time is 5s.

[0066] (3) Room temperature rolling

[0067] The quenched sheet metal is rolled in multiple passes at room temperature, with a single pass deformation of 10% to 20% and a total deformation of 61.5%. This rolling process aims to introduce a high dislocation density, thereby promoting the uniform precipitation of the β'' phase (Mg2Si) in the subsequent aging stage, and obtaining a recycled aluminum alloy sheet metal with a thickness of about 5 mm.

[0068] (4) Artificial aging treatment

[0069] The aging treatment was carried out at 220℃ for a maximum of 30 hours. The defects introduced into the matrix by the previous rolling process acted as heterogeneous nucleation sites during the artificial aging process, which effectively promoted the refinement and dispersion of strengthening phases such as β", while making the Fe-rich phase uniformly distributed in small blocks.

[0070] The peak aging thermal conductivity of the 0.05B-0.6Bi modified recycled aluminum alloy can reach 195 W / (m·K), with a yield strength of 319.8 MPa, an elongation of 6.6%, a C-shaped cutting shape, and an average chip length of 6 mm; it also has excellent machinability. The over-aging thermal conductivity can reach 208 W / (m·K).

[0071] Example 2: Preparation and treatment of recycled high-Fe content Al-Mg-Si based aluminum alloys via 0.05B-0.3Sn microalloying and novel deformation heat treatment process.

[0072] In this embodiment, the composition of the recycled high-Fe content Al-Mg-Si based wrought aluminum alloy is the same as that of Comparative Example 1. The preparation steps of the recycled high-Fe content Al-Mg-Si based aluminum alloy are alloy melting, B-Sn microalloying, homogenization rolling quenching treatment, short-process heat treatment, cold rolling pre-deformation and artificial aging, which simultaneously improve the machinability and thermal conductivity of the recycled high-Fe content Al-Mg-Si based aluminum alloy.

[0073] Specifically, the following steps are included:

[0074] (1) Alloy smelting and casting:

[0075] When the furnace temperature reaches 775℃, add the recycled aluminum alloy and wait for it to melt. When the melt temperature drops to 745℃, simultaneously add Al-3B master alloy and Sn particles with a purity of 99.5%, so that the melt contains 0.05% B and 0.3% Sn (B content is 0.05% of the final product aluminum alloy mass; Sn content is 0.3% of the final product aluminum alloy mass), and let it stand for 25 minutes. Then add a slag remover at a mass ratio of 1:99 (the slag remover is commercially available). (The YT-J-1 refining agent and YT-D-4 refining agent were mixed in a 1:1 mass ratio. After stirring evenly, the mixture was allowed to stand, and the melt temperature was controlled at 735℃~755℃. The slag on the surface of the alloy melt was removed, and then 99.9% argon gas was introduced for refining for 6 minutes. After refining, the slag on the surface of the alloy melt was removed again, and after standing for 6 minutes, the melt at a temperature of 715℃~735℃ was poured into a metal mold preheated to 200℃ for casting, resulting in a recycled high-Fe content Al-Mg-Si based aluminum alloy sheet. Unlike Example 1, Sn particles with a purity of 99.5% were added.

[0076] (2) Short-process heat treatment process including diffusion annealing, rolling, and quenching

[0077] Directional heat treatment was performed on cast recycled aluminum alloy sheets: First, a high-temperature, long-duration diffusion annealing treatment was conducted at 540℃ for 8 hours to ensure sufficient diffusion of elements within the alloy. After diffusion annealing, the sheet was removed from the furnace and immediately subjected to hot rolling with a large deformation of 35% in a single pass. After rolling, it was quickly quenched in room temperature water at 23-33℃ to obtain a recycled aluminum alloy sheet with a thickness of approximately 13mm. Throughout the process, the total heat transfer time from removal from the diffusion annealing furnace to hot rolling and quenching was strictly controlled to ≤12s. Precise time control and parameter matching ensured both microstructure control and dimensional accuracy. The quenching time was 3s, and the hot rolling time was 5s.

[0078] (3) Room temperature rolling

[0079] The quenched sheet metal is rolled in multiple passes at room temperature, with a single pass deformation of 10% to 20% and a total deformation of 61.5%; a recycled aluminum alloy sheet metal with a thickness of about 5 mm is obtained.

[0080] (4) Artificial aging treatment

[0081] Aging treatment is carried out at 220℃ for a maximum of 30 hours.

[0082] The regenerated aluminum alloy modified from 0.05B-0.3Sn-0.6Bi exhibits a peak aging thermal conductivity of 187 W / (m·K), a yield strength of 330.2 MPa, an elongation of 6.3%, a C-shaped cutting profile, an average chip length of 10 mm, and excellent machinability. Over-aging thermal conductivity can reach 206 W / (m·K).

[0083] Example 3: Preparation and treatment of recycled high-Fe content Al-Mg-Si based aluminum alloy by micro-alloying with 0.05B-0.3Sn-0.6Bi and novel deformation heat treatment process.

[0084] In this embodiment, the composition of the recycled high-Fe content Al-Mg-Si based wrought aluminum alloy is the same as that of Comparative Example 1. The preparation steps of the recycled high-Fe content Al-Mg-Si based aluminum alloy are alloy melting, B-Sn microalloying, homogenization rolling quenching treatment, short-process heat treatment, cold rolling pre-deformation and artificial aging, which simultaneously improve the machinability and thermal conductivity of the recycled high-Fe content Al-Mg-Si based aluminum alloy.

[0085] Specifically, the following steps are included:

[0086] (1) Alloy smelting and casting:

[0087] When the furnace temperature reaches 775℃, add the recycled aluminum alloy and wait for it to melt. When the melt temperature drops to the 745℃ range, simultaneously add Al-3B master alloy, 99.5% pure Sn particles, and 99.5% pure Bi particles, resulting in a melt containing 0.05% B, 0.3% Sn, and 0.6% Bi (B content is 0.05% of the final product aluminum alloy mass; Sn content is 0.3% of the final product aluminum alloy mass; Bi content is 0.6% of the final product aluminum alloy mass). Let it stand for 25 minutes. Add the alloy to the melt... A slag remover (comprising a 1:99 mass ratio of commercially available YT-J-1 refining agent and YT-D-4 refining agent mixed in a 1:1 mass ratio) was stirred until homogeneous and allowed to stand. The melt temperature was controlled at 735℃~755℃. Floating slag was skimmed off the surface of the alloy melt, and then 99.9% argon gas was introduced for refining for 6 minutes. After refining, the floating slag was skimmed off again, and the melt was allowed to stand for 6 minutes. The melt at 715℃~735℃ was then poured into a metal mold preheated to 200℃ and cast to obtain a recycled high-Fe content Al-Mg-Si based aluminum alloy sheet. Unlike Example 1, Sn particles with a purity of 99.5% were also added.

[0088] (2) Diffusion annealing, rolling, and quenching – a short-process heat treatment process

[0089] Directional heat treatment was performed on cast recycled aluminum alloy sheets: First, a high-temperature, long-duration diffusion annealing process was conducted, with the annealing temperature set at 540℃ and the holding time at 8 hours. After diffusion annealing, the sheet was removed from the furnace and immediately subjected to hot rolling with a large deformation of 35% in a single pass. After rolling, it was quickly quenched in room temperature water at 23-33℃, ultimately obtaining a recycled aluminum alloy sheet with a thickness of approximately 13mm. Throughout the entire process, the total heat transfer time from removing the sheet from the diffusion annealing furnace to completing hot rolling and then quenching in water was strictly controlled to ≤12s. Through precise time control and parameter matching, both microstructure control and dimensional accuracy were ensured. The quenching time was 3s, and the hot rolling time was 5s.

[0090] (3) Room temperature rolling

[0091] The quenched sheet metal is rolled in multiple passes at room temperature, with a single pass deformation of 10% to 20% and a total deformation of 61.5%; a recycled aluminum alloy sheet metal with a thickness of about 5 mm is obtained.

[0092] (4) Artificial aging treatment

[0093] Aging treatment is carried out at 220℃ for a maximum of 30 hours.

[0094] The regenerated aluminum alloy modified from 0.05B-0.3Sn-0.6Bi exhibits a peak aging thermal conductivity of 194 W / (m·K), a yield strength of 346.8 MPa, an elongation of 9.7%, a C-shaped cutting profile, and an average chip length of 9 mm, demonstrating good machinability. Over-aging thermal conductivity can reach 198 W / (m·K).

[0095] Example 4: Preparation and treatment of recycled high-Fe content Al-Mg-Si based aluminum alloys via 0.05B-0.15Ce microalloying and novel deformation heat treatment process.

[0096] In this embodiment, the composition of the recycled high-Fe content Al-Mg-Si based wrought aluminum alloy is the same as that of Comparative Example 1. The preparation steps of the recycled high-Fe content Al-Mg-Si based aluminum alloy are alloy melting, B-Ce microalloying, homogenization rolling quenching short-process heat treatment, cold rolling pre-deformation and artificial aging, which simultaneously improve the machinability and thermal conductivity of the recycled high-Fe content Al-Mg-Si based aluminum alloy.

[0097] Specifically, the following steps are included:

[0098] (1) Alloy smelting and casting:

[0099] When the furnace temperature reaches 775℃, add the recycled aluminum alloy and wait for it to melt. When the melt temperature drops to 745℃, simultaneously add Al-3B master alloy and Al-20Ce master alloy, so that the melt contains 0.05% B and 0.15% Ce (B content is 0.05% of the final product aluminum alloy mass; Ce content is 0.15% of the final product aluminum alloy mass), and let it stand for 25 minutes. Then add a slag remover at a mass ratio of 1:99 to the melt (the slag remover is commercially available). The alloy was prepared by mixing YT-J-1 and YT-D-4 refining agents in a 1:1 mass ratio, stirring thoroughly, and allowing it to stand. The melt temperature was controlled at 735℃~755℃. The slag on the surface of the alloy melt was removed, and then 99.9% argon gas was introduced for refining for 6 minutes. After refining, the slag on the surface of the alloy melt was removed again, and after standing for 6 minutes, the melt at 715℃~735℃ was poured into a metal mold preheated to 200℃ for casting, resulting in a recycled high-Fe content Al-Mg-Si based aluminum alloy sheet. The difference from Example 1 is that the addition of 99.5% Bi particles was replaced with the addition of Al-20Ce master alloy.

[0100] (2) Short-process heat treatment process including diffusion annealing, rolling, and quenching

[0101] Directional heat treatment was performed on cast recycled aluminum alloy sheets: First, a high-temperature, long-duration diffusion annealing process was conducted at 540℃ for 8 hours. After diffusion annealing, the sheet was removed from the furnace and immediately subjected to hot rolling with a large deformation of 35% in a single pass. Following rolling, the sheet was rapidly quenched in room temperature water (23-33℃) to obtain a recycled aluminum alloy sheet with a thickness of approximately 13mm. Throughout the process, the total heat transfer time from removal from the diffusion annealing furnace to hot rolling and water quenching was strictly controlled to ≤12s. Precise time control and parameter matching ensured both microstructure control and dimensional accuracy. The quenching time was 3s, and the hot rolling time was 5s.

[0102] (3) Room temperature rolling

[0103] The quenched sheet metal is rolled in multiple passes at room temperature, with a single pass deformation of 10% to 20% and a total deformation of 61.5%; a recycled aluminum alloy sheet metal with a thickness of about 5 mm is obtained.

[0104] (4) Artificial aging treatment

[0105] Aging treatment is carried out at 220℃ for a maximum of 30 hours.

[0106] The peak aging thermal conductivity of the 0.05B-0.15Ce modified recycled aluminum alloy can reach 192 W / (m·K), with a yield strength of 314.8 MPa, an elongation of 9.6%, a C-shaped cutting shape, and an average chip length of 9 mm, exhibiting good machinability. The over-aging thermal conductivity can reach 201 W / (m·K).

[0107] Example 5:

[0108] In this embodiment, the composition of the recycled high-Fe content Al-Mg-Si based wrought aluminum alloy is the same as in Example 1. The difference is that the quenching time in this embodiment is 10 seconds, and the alloy casting and deformation heat treatment processes are the same as in Example 1.

[0109] By extending the quenching time, the alloy can achieve a balance between hardness and plasticity through subsequent aging treatment: the matrix is ​​moderately strengthened by the precipitation of dispersed Mg2Si phase, avoiding the problem of tool sticking due to insufficient hardness, while avoiding tool chipping caused by over-hardening; the uniform distribution of spherical α-AlFeSi phase can play the role of "chip breaking point", causing the chip to undergo embrittlement fracture during cutting, improving the chip's manufacturability, and the scraping effect of spherical phase on the tool is much lower than that of acicular phase, which can significantly reduce the tool wear rate and extend the tool life.

[0110] The peak aged thermal conductivity reaches 180 W / (m·K), the peak aged yield strength is 321.2 MPa, and it also has an elongation of 6.8%. The cutting shape is C-shaped, with an average chip length of 8 mm, exhibiting good machinability. The over-aged thermal conductivity can reach 199 W / (m·K).

[0111] The performance data of the alloys prepared in Comparative Example 1 and Examples 1-5 are summarized in Table 1.

[0112] Table 1. Properties of alloys prepared in Comparative Examples 1 and Examples 1-5

[0113]

[0114] To further illustrate the effects of this invention, different alloy preparation methods and heat treatment processes are also provided and compared.

[0115] Comparative Example 2:

[0116] The composition of the recycled high-Fe content Al-Mg-Si based wrought aluminum alloy in this comparative example is the same as that in Comparative Example 1. The alloy melting and casting in this comparative example are the same as in Comparative Example 1; the difference lies in the heat treatment process, which is the same as in Example 1.

[0117] The heat treatment process in this comparative example differs from that in Comparative Example 1. The synergistic design of "high-temperature diffusion annealing + large deformation single hot rolling" simultaneously achieves Fe phase transformation, microstructure refinement, and preservation of high-density dislocation structure within a shorter process. It focuses on synergistically improving the alloy's machinability and thermal conductivity by optimizing the Fe phase morphology and utilizing dislocation strengthening. The alloy's peak-aged thermal conductivity is 178 W / (m·K), with an elongation of 7.8%. Compared to the peak-aged alloy of Comparative Example 1, the peak-aged alloy of Comparative Example 2 exhibits a 1 W / (m·K) increase in thermal conductivity, a long-wide strip-shaped cutting shape, an average chip length of 100 mm, and poor machinability. After long-term aging (over-aging), the thermal conductivity is 187 W / (m·K).

[0118] Comparative Example 3:

[0119] The composition of the recycled high-Fe content Al-Mg-Si based wrought aluminum alloy in this comparative example is the same as that in Comparative Example 1. The difference is that Al-3B master alloy and Al-10Sr master alloy are added during the smelting process in this comparative example (the content of B is 0.05% of the mass of the final product aluminum alloy; the content of Sr is 0.05% of the mass of the final product aluminum alloy). The alloy casting and deformation heat treatment processes are the same as those in Comparative Example 1.

[0120] To reduce interface defects and purify the alloy melt, this comparative example introduced synergistic regulation using boron (B) and sir (Sr) elements: B purifies the melt by forming and filtering borides; Sr reduces its adverse effects on thermal conductivity by refining the Fe-rich phase and eutectic silicon. The peak-aged thermal conductivity reached 184 W / (m·K). Compared to the peak-aged alloy of Comparative Example 1, the peak-aged alloy of Comparative Example 3 showed a 7 W / (m·K) increase in thermal conductivity, a medium-long, thin strip-shaped cutting profile, an average chip length of 20 mm, and poor machinability. The thermal conductivity after long-term aging (over-aging) was 195 W / (m·K).

[0121] The performance data of the alloys prepared in Comparative Examples 1-3 and Example 1 are shown in Table 2.

[0122] Table 2 shows the properties of the alloys prepared in Comparative Examples 1-3 and Example 1.

[0123]

[0124] Figure 3 The chip morphology of the alloy in Comparative Example 1 after heat treatment is shown. Figure 4 The chip morphology of the alloy in Comparative Example 2 after heat treatment is shown. Figure 5 The chip morphology of the alloy in Comparative Example 3 after heat treatment is shown. Figure 6 The chip morphology of the alloy in Example 1 after heat treatment; Figure 7 The chip morphology of the alloy in Example 2 after heat treatment; Figure 8 The chip morphology of the alloy in Example 3 after heat treatment; Figure 9 The image shows the chip morphology of the alloy in Example 4 after heat treatment.

[0125] The implementation of the present invention is not limited to the embodiments described above. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for simultaneously improving the machinability and thermal conductivity of recycled high-Fe content Al-Mg-Si based aluminum alloys, characterized in that: Includes the following steps: 1) Remelting recycled high-Fe content Al-Mg-Si based aluminum alloy yields a recycled aluminum alloy melt. The recycled high-Fe content Al-Mg-Si based aluminum alloy consists of the following components by mass percentage: Si 0.65%~0.75%, Fe 0.85%~1.05%, Mg 0.75%~0.85%, Cu 0.32%~0.42%, Mn 0.25%~0.35%, Cr 0.15%~0.25%, Zn 0.35%~0.45%, Ni 0.15%~0.25%, Ti 0.25%~0.35%, V 0.15%~0.25%, Pb 0.35%~0.45%, Zr 0.15%~0.25%; the total mass of unavoidable impurities is ≤0.5wt.%, with the balance being Al. 2) Add a master alloy containing B and a metal containing R, or a master alloy containing B and a master alloy containing Ce, to the recycled aluminum alloy melt, and perform microalloying treatment at 735℃~775℃; the metal containing R is Bi and / or Sn; the amount of B added is 0.04%~0.06% of the mass of the final product aluminum alloy; when the metal containing R is Bi and / or Sn, the amount of Bi added is 0.55%~0.65% of the mass of the final product aluminum alloy, and the amount of Sn added is 0.25%~0.35% of the mass of the final product aluminum alloy; the microalloying refers to holding at 735℃~775℃ for 15~40 minutes; the amount of Ce added is 0.14%~0.16% of the mass of the final product aluminum alloy. 3) Remove slag from the melt obtained in step (2), refine it, and cast it to obtain recycled deformed aluminum alloy sheet. 4) The recycled deformed aluminum alloy sheet from step 3) undergoes high-temperature homogenization annealing, followed immediately by large-deformation hot rolling and rapid quenching to obtain a rolled and quenched sheet. The homogenization annealing temperature in step 4) is 525~565℃. The large-deformation hot rolling refers to taking the homogenized annealed aluminum alloy sheet out of the homogenization furnace and directly performing a single large-deformation rolling of 30~40%. Quenching refers to rapidly immersing the sheet in water at 23~33℃ after hot rolling. The total time for the aluminum alloy sheet to be taken out of the homogenization furnace, hot rolled, and quenched does not exceed 12s. The hot rolling time is 3-5s, and the quenching time is 2~7s. 5) The sheet material from step 4) is subjected to room temperature rolling and artificial aging treatment to obtain the final recycled aluminum alloy; the room temperature rolling mentioned in step 5) refers to the aluminum alloy sheet being rolled 5 to 7 times after quenching, with a total rolling amount of 60 to 67%.

2. The method for simultaneously improving the machinability and thermal conductivity of recycled high-Fe content Al-Mg-Si based aluminum alloys according to claim 1, characterized in that: In step 2), the temperature for microalloying treatment is 735~755℃; the holding time is 20~30min. The homogenization annealing temperature in step 4) is 535~545℃, and the annealing time is 7.5~8.5h; The room temperature rolling process described in step 5) is performed 6 times, with a deformation amount of 10-20% per rolling process.

3. The method for simultaneously improving the machinability and thermal conductivity of recycled high-Fe content Al-Mg-Si based aluminum alloys according to claim 1, characterized in that: The temperature for artificial aging in step 5) is 185℃~235℃, and the artificial aging time is 0.1~30h; Step 2) The B-containing master alloy is an Al-3B master alloy, with Bi and Sn being 99.5% pure Bi particles and 99.5% pure Sn particles, respectively; the Ce-containing master alloy is an Al-20Ce master alloy.

4. The method for simultaneously improving the machinability and thermal conductivity of recycled high-Fe content Al-Mg-Si based aluminum alloys according to claim 3, characterized in that: The temperature for artificial aging is 215~235℃, and the artificial aging time is 0.5~4h.

5. The method for simultaneously improving the machinability and thermal conductivity of recycled high-Fe content Al-Mg-Si based aluminum alloys according to claim 1, characterized in that: The remelting temperature mentioned in step 1) is 730-785℃, and the remelting time is 1.5~2.5h.

6. The method for simultaneously improving the machinability and thermal conductivity of recycled high-Fe content Al-Mg-Si based aluminum alloys according to claim 1, characterized in that: Step 3) involves the following steps: adding a slag remover to the melt, stirring until homogeneous, allowing it to stand, removing the slag, and then refining it by introducing argon gas. After refining, the slag is removed and the melt is allowed to stand. Subsequently, the melt is cast into a preheated mold to obtain a recycled deformed aluminum alloy sheet.

7. The method for simultaneously improving the machinability and thermal conductivity of recycled high-Fe content Al-Mg-Si based aluminum alloys according to claim 6, characterized in that: The slag-removing agent is prepared by mixing commercially available YT-J-1 refining agent and YT-D-4 refining agent in a mass ratio of 1:1; the refining refers to the introduction of 99.99% high-purity argon gas for 3-9 minutes; the slag removal and settling time after refining is 3-9 minutes. The preheating temperature of the mold is 185-285℃, and the temperature of the melt during casting is 715℃~735℃.

8. The method for simultaneously improving the machinability and thermal conductivity of recycled high-Fe content Al-Mg-Si based aluminum alloys according to claim 1, characterized in that: The mass ratio of the slag remover to the melt is (0.5~1.5):99; Argon gas is introduced for 5-7 minutes; slag is removed and allowed to stand for 5-7 minutes.

9. A recycled high-Fe-content Al-Mg-Si based aluminum alloy with high machinability and thermal conductivity obtained by the method described in any one of claims 1 to 8.

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