Method for controlling morphology of iron-rich phase in recycled aluminum alloy and application thereof

Abstract

This invention discloses a method and application for controlling the morphology characteristics of iron-rich phases in recycled aluminum alloys. The control method includes at least: casting raw materials into ingots using directional solidification; in the directional solidification, the cooling rate is 1 k / s–20 k / s; in the chemical composition of the recycled aluminum alloy, the mass ratio of Fe to Mn is less than or equal to 3.5; and heat-treating the ingots. This invention innovatively designs a correlation rule between "cooling rate – Fe / Mn ratio – iron-rich phase morphology," introducing the "shape factor (SF)" from image analysis technology as an objective standard for defining the morphology of iron-rich phases. It establishes a mathematical relationship between the SF values ​​of the 20 largest iron-rich phases in the alloy under multiple cooling rates and the Fe / Mn ratio, constructing a quantitative mapping relationship and a predictable "process control window" linking composition, process parameters, and the final microstructure. This helps technicians design corresponding process parameters according to actual needs.

Description

Technical Field

[0001] This invention belongs to the field of recycled aluminum alloy technology, specifically relating to a method and application for controlling the morphological characteristics of iron-rich phases in recycled aluminum alloys. Background Technology

[0002] Recycled aluminum alloys are increasingly widely used in the automotive, aerospace, and electronics industries due to their advantages in resource recycling and energy conservation and emission reduction. However, recycled aluminum raw materials often contain high levels of impurity elements such as Fe, which easily form iron-rich phases (such as β-Al5FeSi) during solidification. These phases typically exhibit coarse needle-like or elongated morphologies, severely disrupting the aluminum matrix and leading to a significant decrease in the mechanical properties of the alloy, especially its toughness and fatigue performance.

[0003] In recent years, with the increasing proportion of recycled aluminum used, effectively controlling the morphology of the iron-rich phase has become a hot research topic in the industry. Existing research shows that by adjusting the alloy composition (such as adding elements like Mn and Cr), the harmful effects of Fe can be partially neutralized, promoting the transformation of the iron-rich phase from needle-like to Chinese character-like or rounded dot-like structures. However, the morphology of the iron-rich phase is not only affected by composition but also strongly dependent on the casting process. Currently, a mapping relationship between "composition-process-iron-rich phase morphology" has not been established, especially in multi-component recycled aluminum alloy systems, where constructing a reliable process control window remains a technical challenge. Summary of the Invention

[0004] The purpose of this invention is to provide a method and application for controlling the morphological characteristics of iron-rich phases in recycled aluminum alloys. This invention systematically establishes the correlation rules between the morphology of iron-rich phases in recycled aluminum alloys and key process parameters (such as cooling rate and Fe / Mn ratio), which has important theoretical value and engineering significance.

[0005] To achieve the above objectives, a specific embodiment of the present invention provides the following technical solution:

[0006] A method for controlling the morphological characteristics of iron-rich phases in recycled aluminum alloys, the method comprising at least:

[0007] The raw materials are cast into ingots using a directional solidification method; in the directional solidification method, the cooling rate is 1 k / s-20 k / s; in the chemical composition of the recycled aluminum alloy, the mass ratio of Fe to Mn is less than or equal to 3.5;

[0008] The ingot is heat-treated.

[0009] In one or more embodiments of the present invention, the mass ratio of Fe to Mn in the chemical composition of the recycled aluminum alloy is 0.5-3.5.

[0010] In one or more embodiments of the present invention, the mass ratio of Fe to Mn is 0.5-3.5, and the cooling rate is 1k / s-2k / s;

[0011] The shape factor SF of the iron-rich phase in the recycled aluminum alloy satisfies: SF = 0.43-0.09 (Fe / Mn).

[0012] In one or more embodiments of the present invention, the mass ratio of Fe to Mn is 0.5-3.5, and the cooling rate is 5k / s-6k / s;

[0013] The shape factor SF of the iron-rich phase in the recycled aluminum alloy satisfies: SF = 0.46-0.08 (Fe / Mn).

[0014] In one or more embodiments of the present invention, the mass ratio of Fe to Mn is 0.5-3.5, and the cooling rate is 18k / s-20k / s;

[0015] The shape factor SF of the iron-rich phase in the recycled aluminum alloy satisfies: SF = 0.74-0.17 (Fe / Mn).

[0016] In one or more embodiments of the present invention, the heat treatment includes solution treatment and aging treatment.

[0017] In one or more embodiments of the present invention, the solution treatment includes a first-stage solution treatment and a second-stage solution treatment. The conditions for the first-stage solution treatment are: temperature 300℃-400℃, time 4h-8h; and the conditions for the second-stage solution treatment are: temperature 515℃-535℃, time 5h-10h.

[0018] The heating rate in the first-stage solution treatment and / or the second-stage solution treatment is 160℃ / h-180℃ / h.

[0019] In one or more embodiments of the present invention, the aging treatment conditions are: temperature 170℃-200℃, time 6h-10h; and / or,

[0020] In the aging process, the heating rate is 160℃ / h-180℃ / h.

[0021] In one or more embodiments of the present invention, the chemical composition of the recycled aluminum alloy, by mass percentage, includes: Si 6-7 wt.%, Cu 0.4-0.6 wt.%, Mg 0.3-0.5 wt.%, Zn 0.25-0.35 wt.%, Mn 0.15-0.25 wt.%, Cr 0.05-0.15 wt.%, Sr 150-200 ppm, Fe 0-0.7 wt.%, trace element X1, trace element X2, with the balance being Al and unavoidable impurities;

[0022] Wherein, the trace element X1 is at least one of Te and B, and the content of either Te or B is 0-300 ppm;

[0023] The trace element X2 is at least one of Sb and Be, and the content of either Sb or Be is 0-200 ppm.

[0024] In one or more embodiments of the present invention, either the Te content or the B content is 100-300 ppm; and / or,

[0025] The content of either Sb or Be is 100-200 ppm.

[0026] In one or more embodiments of the present invention, the iron-rich phase morphology includes at least one of granular, short needle-like, and long needle-like shapes.

[0027] Another specific embodiment of the present invention provides the following technical solution:

[0028] Application of a method for controlling the morphological characteristics of iron-rich phases in recycled aluminum alloys in the preparation of recycled aluminum alloys.

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

[0030] 1. This invention quantifies the relationship between "cooling rate - Fe / Mn ratio - iron-rich phase morphology" through a mathematical model. This changes the previous experience-based and wide-ranging control mode and enables accurate prediction of microstructure.

[0031] 2. This invention constructs a calculable control window: the provided calculation formulas (the correspondence between cooling rate, Fe / Mn ratio, and SF value of iron-rich phase) constitute a calculable dynamic process window. Engineers can query this window in reverse order based on the final product's microstructure requirements, actively selecting the casting process (cooling rate) and designing the composition (controlling the Fe / Mn ratio) to efficiently obtain the ideal microstructure. Simultaneously, this patent employs directional solidification, controlling the cooling rate within three typical rate ranges with orders of magnitude difference: 1k / s-2k / s, 5k / s-6k / s, and 18k / s-20k / s. This simulates industrial scenarios ranging from gravity casting (cooling rate approximately 1k / s) to low-pressure casting (cooling rate approximately 5k / s) and squeeze casting (cooling rate approximately 20k / s), providing guidance for various casting processes.

[0032] 3. This invention introduces advanced characterization and modeling methods: This invention abandons the traditional, subjective "point-like" and "needle-like" descriptions and introduces the shape factor (SF), an objective image analysis quantification index, to define the morphology of iron-rich phases. It limits the statistical and modeling of the key microscopic characteristic parameter, the average SF value of the 20 largest iron-rich phases, to grasp the main contradictions affecting macroscopic performance, making the control method more scientific and effective. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram illustrating the expression of Shape Factor in this invention;

[0035] Figure 2 These are room temperature microstructure images of the alloys in Examples 1-3 of this invention;

[0036] Figure 3 These are room temperature microstructure images of the alloys in Examples 4-5 of this invention;

[0037] Figure 4 This is a room temperature microstructure diagram of the alloy in Comparative Example 1 of the present invention;

[0038] Figure 5 This is a room temperature microstructure diagram of the alloy in Comparative Example 2 of the present invention;

[0039] Figure 6This is a cloud diagram showing the relationship between the Fe / Mn ratio and cooling rate of the present invention and the average SF value of the 20 largest iron-rich phases in the alloy. Detailed Implementation

[0040] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions in the embodiments of this disclosure are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0041] The morphology of the iron-rich phase in recycled aluminum alloys is not only affected by the composition, but also strongly depends on the casting process, such as the cooling rate during solidification. At present, the mapping relationship between "composition-process-iron-rich phase morphology" has not been established. In particular, in multi-component recycled aluminum alloy systems, how to construct a reliable process control window remains a technical challenge.

[0042] Currently, existing technologies either focus on composition adjustment or process optimization, failing to systematically study both as an organic whole. Composition design often provides a broad, static optimal range, while process parameters (such as cooling rate) are only limited to an optimal range. This control mode makes it impossible for those skilled in the art to predict what iron-rich phase morphology will be obtained under specific combinations of composition (such as Fe / Mn ratio) and process (such as cooling rate) when facing specific production conditions. The entire process still relies on an "experience-trial and error" model. Furthermore, existing technologies describe iron-rich phase morphologies as "needle-like," "blocky," or "Chinese character-like" primarily qualitatively and subjectively, lacking unified and objective quantitative criteria. This leads to poor data comparability between different studies, low process reproducibility, and difficulty in achieving stable and precise quality control.

[0043] This invention innovatively designs a correlation rule between "cooling rate - Fe / Mn ratio - morphology of iron-rich phases". By introducing "shape factor (SF)" from image analysis technology as an objective standard to define the morphology of iron-rich phases, it establishes a mathematical relationship between the SF values ​​of the 20 largest iron-rich phases in the alloy under multiple cooling rates and the Fe / Mn ratio. This constructs a quantitative mapping relationship linking composition, process parameters and final microstructure, and a predictable "process control window", which helps technicians design corresponding process parameters according to actual needs.

[0044] Specifically, the sources of recycled aluminum are complex. Iron, as the most common impurity, has a highly fluctuating content and is difficult to remove economically. Iron has extremely low solid solubility in aluminum, inevitably forming intermetallic compounds during solidification. The morphology and size of the iron-rich phase are strongly dependent on the solidification cooling rate and composition design (such as the Fe / Mn ratio). Achieving accurate prediction and control of the morphology of the iron-rich phase is a prerequisite for the stable production of high-performance recycled aluminum products.

[0045] The Fe / Mn ratio of the alloy determines whether, under thermodynamic equilibrium conditions, the iron-rich phase tends to form either a needle-like β-Al₅FeSi phase or a Chinese character-shaped α-Al phase. 15 (Fe,Mn)3Si2 phase. At low Fe / Mn ratios, Mn atoms dissolve extensively into the iron-rich phase, thermodynamically stabilizing the α phase. The rounded α phase significantly reduces its disruptive effect on the aluminum matrix, greatly improving the alloy's ductility and toughness while maintaining strength. However, at high Fe / Mn ratios, insufficient Mn content fails to effectively suppress the formation of the β phase. The β phase exhibits strong anisotropic growth characteristics, tending to grow into sharp needle-like or lamellar shapes along specific crystal orientations. These needle-like β phases severely disrupt the matrix, becoming stress concentration points and crack initiation sites, leading to a sharp deterioration in the alloy's ductility, toughness, and fatigue properties.

[0046] Cooling rate kinetically controls the nucleation, growth, and phase selection of iron-rich phases by influencing diffusion and undercooling during solidification. High cooling rates (e.g., 20 K / s) result in higher undercooling, increased nucleation rate, and significantly refined iron-rich phases. Simultaneously, the extremely short atomic diffusion time during rapid solidification inhibits the formation and coarsening of acicular β-Al₅FeSi phases, as their formation depends on long-range diffusion of solute atoms and specific crystallographic orientations. In contrast, bulk / Chinese character-shaped α-Al₅FeSi phases exhibit more robust growth. 15 The (Fe,Mn)3Si2 phase is more likely to form a fine, equiaxed morphology at a high nucleation rate. At a low cooling rate (e.g., 1 k / s), the undercooling is small, the nucleation rate is low, and atoms have sufficient time to diffuse, which provides conditions for the growth and coarsening of the β phase.

[0047] A specific embodiment of the present invention provides a method for controlling the morphological characteristics of iron-rich phases in recycled aluminum alloys, which specifically includes the following steps:

[0048] Step 1: Cast the raw materials into ingots using directional solidification. In directional solidification, the cooling rate is 1k / s-20k / s. In the chemical composition of the recycled aluminum alloy, the mass ratio of Fe to Mn is less than or equal to 3.5.

[0049] Specifically, the chemical composition of recycled aluminum alloy, by mass percentage, includes: Si 6-7 wt.%, Cu 0.4-0.6 wt.%, Mg 0.3-0.5 wt.%, Zn 0.25-0.35 wt.%, Mn 0.15-0.25 wt.%, Cr 0.05-0.15 wt.%, Sr 150-200 ppm, Fe 0-0.7 wt.%, trace element X1, trace element X2, with the balance being Al and unavoidable impurities, and the total content of impurity elements other than Fe not exceeding 0.2%.

[0050] Wherein, trace element X1 is at least one of Te and B, with the content of Te being 0-300 ppm, preferably 100-300 ppm, specifically any one of 50 ppm, 100 ppm, and 300 ppm; the content of B is 0-300 ppm, preferably 100-300 ppm, specifically any one of 50 ppm, 100 ppm, and 300 ppm. Trace element X2 is at least one of Sb and Be, with the content of Sb being 0-200 ppm, preferably 100-200 ppm, specifically any one of 50 ppm, 100 ppm, and 200 ppm; the content of Be is 0-200 ppm, preferably 100-200 ppm, specifically any one of 50 ppm, 100 ppm, and 200 ppm.

[0051] For example, the Si element content can be any one of 6-6.5 wt.% or 6.5-7 wt.%, specifically any one of 6 wt.%, 6.5 wt.%, or 7 wt.%. The Cu element content can be any one of 0.4-0.5 wt.% or 0.5-0.6 wt.%, specifically any one of 0.4 wt.%, 0.5 wt.%, or 0.6 wt.%. The Mg element content can be any one of 0.3-0.4 wt.% or 0.4-0.5 wt.%, specifically any one of 0.3 wt.%, 0.4 wt.%, or 0.5 wt.%. The Zn element content can specifically be any one of 0.25 wt.%, 0.30 wt.%, or 0.35 wt.%. The Mn element content can be any one of 0.15 wt.%, 0.20 wt.%, or 0.25 wt.%. The Cr element content can be any one of 0.05 wt.%, 0.10 wt.%, or 0.15 wt.%. The Sr element content can be any one of 150-170ppm, 160-190ppm, or 180-200ppm, specifically any one of 150ppm, 160ppm, 170ppm, 180ppm, 190ppm, or 200ppm. The Fe element content can be any one of 0.1-0.7wt.% or 0.4-0.6wt.%, specifically any one of 0.1wt.%, 0.4wt.%, 0.6wt.%, or 0.7wt.%.

[0052] Furthermore, in the chemical composition of recycled aluminum alloys, the mass ratio of Fe to Mn is 0.5-3.5.

[0053] Furthermore, in this invention, the Fe / Mn mass ratio and the cooling rate do not act independently, but are synergistically controlled, achieving optimal alloy properties through a specific combination. The relationship between the Fe / Mn ratio and the cooling rate constitutes a predictable and operable "process control window," guiding producers to proactively design the desired microstructure by adjusting these two key parameters.

[0054] Specifically, to ensure the reliability of the statistical data, a shape factor (SF value) was introduced: provided the Fe-containing phase outlines were clear, 10 SEM images were stitched together, with at least 500 Fe-containing phases for each component included in the statistics. The quantity, size, and shape of all Fe-containing phases were quantitatively analyzed, with the shape of the Fe-containing phases characterized using a shape factor, such as... Figure 1 As shown, the closer the particle shape is to a circle, the closer its SF value is to 1, and vice versa. Among these, Area refers to the area containing the Fe phase, and Convex hull perimeter refers to the perimeter of the smallest convex polygon that encloses the iron-containing phase.

[0055] The correlation between the Fe / Mn ratio, cooling rate, and morphology of the iron-rich phase is as follows: when the cooling rate is 1 k / s-2 k / s, the corresponding correlation spectrum is SF=0.43-0.09 (Fe / Mn), where SF is the average SF value of the 20 largest iron-rich phases in the alloy, and 0.5≤(Fe / Mn)≤3.5. Preferably, when (Fe / Mn)≤1.10, the iron-rich phase in the alloy is in the form of rounded granules and short needles.

[0056] When the cooling rate is 5k / s-6k / s, the corresponding relationship spectrum is SF=0.46-0.08 (Fe / Mn), where SF value is the average SF value of the 20 largest iron-rich phases in the alloy, and 0.5≤(Fe / Mn)≤3.5. Preferably, when (Fe / Mn)≤1.5, the iron-rich phases in the alloy are in the form of rounded granules and short needles.

[0057] When the cooling rate is 18k / s-20k / s, the corresponding relationship spectrum is SF=0.74-0.17 (Fe / Mn), where SF value is the average SF value of the 20 largest iron-rich phases in the alloy, and 0.5≤(Fe / Mn)≤3.5. Preferably, when (Fe / Mn)≤2.35, the iron-rich phases in the alloy are in the form of rounded granules and short needles.

[0058] Step 2: Heat treat the ingot.

[0059] Specifically, the heat treatment includes solution treatment and aging treatment. The solution treatment includes a first-stage solution treatment and a second-stage solution treatment. The conditions for the first-stage solution treatment are: temperature 300℃-400℃, time 4h-8h; the conditions for the second-stage solution treatment are: temperature 515℃-535℃, time 5h-10h. The heating rate for both stages of solution treatment is controlled at 160℃ / h-180℃ / h, and rapid quenching is performed after the holding time.

[0060] The aging treatment conditions are: temperature 170℃-200℃, time 6h-10h, and heating rate of 160℃ / h-180℃ / h.

[0061] Another specific embodiment of the present invention provides a method for controlling the morphological characteristics of iron-rich phases in recycled aluminum alloys, which is applied in the preparation of recycled aluminum alloys.

[0062] The present invention will be further described in detail below with reference to specific embodiments.

[0063] Unless otherwise specified, all raw materials used in this invention are general-purpose materials and can be obtained commercially.

[0064] In this invention, field emission scanning electron microscopy (SEM) is used to capture the microstructure of the alloy, and image processing software is used to evaluate the morphology and size of the iron-rich phases. To ensure the reliability of the statistical data, 10 SEM images are stitched together, provided that the outlines of the Fe-containing phases are clear. At least 500 Fe-containing phases for each component are included in the statistics, and the quantity, size, and shape of all Fe-containing phases are quantitatively analyzed.

[0065] Example 1

[0066] The content of each element in the cast aluminum alloy by mass percentage is shown in Table 1 below, with the balance being Al and other unavoidable impurities other than Fe.

[0067] The specific smelting steps of the alloy in this embodiment include:

[0068] A356 alloy ingots, pure Cu, and metallic silicon were placed in a melting furnace at a temperature of 760°C. After the raw materials melted, Al-10Mn, Al-10Cr, Al-10Ni, Al-10Fe, and Al-10Sb master alloys were added and held at this temperature for 5 minutes. After complete melting, the temperature was lowered to 725°C, and pure Mg and Zn ingots wrapped in aluminum foil were added. The mixture was manually stirred for 5 minutes to ensure homogeneity, and then allowed to stand for further heating to prepare for degassing. When the melt temperature reached 740°C, a general-purpose refining agent (chloride refining agent, DURSALIT R LM 14 F Granules) was added externally to the alloy melt using a rotary argon injection method for refining and slag removal. The amount of refining agent added was 1.5 wt.‰ of the alloy melt weight.

[0069] To reduce Sr burn-off during degassing, after 5 minutes of degassing, 0.15 wt.% of dried Al-10Sr modifier was added to the melt. After 15 minutes of degassing, another 0.15 wt.% of dried Al-10Sr modifier was added. After 25 minutes of degassing, 0.3 wt.% of dried Al-5Ti-B refining agent was added, and degassing continued for another 5 minutes before completion. The melt was allowed to stand for 5 minutes before slag removal began. After slag removal, the melt was poured into a water-cooled copper mold, and a φ7mm×150mm cylindrical ingot was removed from the mold. After smelting, one ingot was selected for directional solidification experiments, with the cooling rate controlled at 20 kJ / s.

[0070] The ingots obtained by directional solidification are subjected to the following heat treatment process: the first stage solution temperature is 300℃ and the holding time is 8h; the second stage solution temperature is 535℃ and the holding time is 6h; the heating rate of both stages of solution is controlled at 180℃ / h, and the quenching process is adopted after the holding time is completed.

[0071] After quenching, an aging treatment was performed: the temperature was held at 170℃ for 10 hours, with the heating rate controlled at 180℃ / h. After cooling, samples were taken from the ingot for microstructure observation.

[0072] The room temperature microstructure of the alloy prepared in this embodiment is as follows: Figure 2 As shown in a and 2b, the statistical results of the microstructure are shown in Table 2. In Table 2, the Mn / Fe ratio of the iron-rich phase refers to the ratio of Mn and Fe in the iron-rich phase.

[0073] Example 2

[0074] The content of each element in the cast aluminum alloy by mass percentage is shown in Table 1 below, with the balance being Al and other unavoidable impurities other than Fe.

[0075] The specific smelting steps of the alloy in this embodiment include:

[0076] A356 alloy ingots, pure Cu, and metallic silicon were placed in a melting furnace at 750°C. After the raw materials melted, Al-10Mn, Al-10Cr, Al-10Ni, Al-10Fe, and Al-5Be master alloys were added and held at that temperature for 5 minutes. After complete melting, the temperature was lowered to 728°C, and pure Mg and Zn ingots wrapped in aluminum foil were added. The mixture was manually stirred for 5 minutes to ensure homogeneity, and then allowed to stand for further heating to prepare for degassing. When the melt temperature reached 745°C, a general-purpose refining agent (chloride refining agent, DURSALIT R LM 14 F Granules) was added externally to the alloy melt using a rotary argon injection method for refining and slag removal. The amount of refining agent added was 1.5 wt.‰ of the alloy melt weight.

[0077] To reduce Sr burn-off during degassing, after 5 minutes of degassing, 0.15 wt.% of dried Al-10Sr modifier was added to the melt. After 15 minutes of degassing, another 0.15 wt.% of dried Al-10Sr modifier was added. After 25 minutes of degassing, 0.3 wt.% of dried Al-5Ti-B refining agent was added, and degassing continued for another 5 minutes before completion. The melt was allowed to stand for 5 minutes before slag removal began. After slag removal, the melt was poured into a water-cooled copper mold, and a φ7mm×150mm cylindrical ingot was removed from the mold. After smelting, one ingot was selected for directional solidification experiments, with the cooling rate controlled at 20 kJ / s.

[0078] The ingots obtained by directional solidification are subjected to the following heat treatment process: the first stage solution temperature is 400℃ and the holding time is 8h; the second stage solution temperature is 515℃ and the holding time is 6h; the heating rate of both stages of solution is controlled at 170℃ / h, and the quenching process is adopted after the holding time is completed.

[0079] After quenching, an aging treatment was performed: the temperature was held at 180℃ for 8 hours, with the heating rate controlled at 175℃ / h. After cooling, samples were taken from the ingot for microstructure observation.

[0080] The room temperature microstructure of the alloy prepared in this embodiment is as follows: Figure 2 As shown in c and 2d, the statistical results of microstructure are shown in Table 2.

[0081] Example 3

[0082] The content of each element in the cast aluminum alloy by mass percentage is shown in Table 1 below, with the balance being Al and other unavoidable impurities other than Fe.

[0083] The specific smelting steps of the alloy in this embodiment include:

[0084] A356 alloy ingots, pure Cu, and metallic silicon were placed in a melting furnace at a temperature of 755°C. After the raw materials melted, Al-10Mn, Al-10Cr, Al-10Ni, Al-10Fe, and Al-10Te master alloys were added and melted. After complete melting, the temperature was lowered to 720°C, and pure Mg and Zn ingots wrapped in aluminum foil were added. The mixture was manually stirred for 5 minutes to ensure homogeneity, and then allowed to stand for further heating to prepare for degassing. When the melt temperature reached 735°C, a general-purpose refining agent (chloride refining agent, DURSALIT R LM 14 F Granules) was added externally to the alloy melt using a rotary argon injection method for refining and slag removal. The amount of refining agent added was 1.5 wt.‰ of the alloy melt weight.

[0085] To reduce Sr burn-off during degassing, after 5 minutes of degassing, 0.15 wt.% of dried Al-10Sr modifier was added to the melt. After 15 minutes of degassing, another 0.15 wt.% of dried Al-10Sr modifier was added. After 25 minutes of degassing, 0.3 wt.% of dried Al-5Ti-B refining agent was added, and degassing continued for another 5 minutes before completion. The melt was allowed to stand for 5 minutes before slag removal began. After slag removal, the melt was poured into a water-cooled copper mold, and a φ7mm×150mm cylindrical ingot was removed from the mold. After smelting, one ingot was selected for directional solidification experiments, with the cooling rate controlled at 20 kJ / s.

[0086] The ingots obtained by directional solidification are subjected to the following heat treatment process: the first stage solution temperature is 350℃ and the holding time is 6h; the second stage solution temperature is 520℃ and the holding time is 8h; the heating rate of both stages of solution is controlled at 165℃ / h, and the quenching process is adopted after the holding time is completed.

[0087] After quenching, an aging treatment was performed: the temperature was held at 190℃ for 7 hours, with the heating rate controlled at 160℃ / h. After cooling, samples were taken from the ingot for microstructure observation.

[0088] The room temperature microstructure of the alloy prepared in this embodiment is as follows: Figure 2 As shown in e and 2f, the statistical results of microstructure are shown in Table 2.

[0089] Example 4

[0090] The content of each element in the cast aluminum alloy by mass percentage is shown in Table 1 below, with the balance being Al and other unavoidable impurities other than Fe.

[0091] The specific smelting steps of the alloy in this embodiment include:

[0092] A356 alloy ingots, pure Cu, and metallic silicon were placed in a melting furnace at a temperature of 765°C. After the raw materials melted, Al-10Mn, Al-10Cr, Al-10Ni, Al-10Fe, and Al-3B master alloys were added and melted. After complete melting, the temperature was lowered to 720°C, and pure Mg and Zn ingots wrapped in aluminum foil were added. The mixture was manually stirred for 5 minutes to ensure homogeneity, and then allowed to stand for further heating to prepare for degassing. When the melt temperature reached 740°C, a general-purpose refining agent (chloride refining agent, DURSALIT R LM 14 F Granules) was added externally to the alloy melt using a rotary argon injection method for refining and slag removal. The amount of refining agent added was 1.5 wt.‰ of the alloy melt weight.

[0093] To reduce Sr loss during degassing, after 5 minutes of degassing, 0.15 wt.% of dried Al-10Sr modifier was added to the melt. After 15 minutes of degassing, another 0.15 wt.% of dried Al-10Sr modifier was added. After 25 minutes of degassing, 0.3 wt.% of dried Al-5Ti-B refining agent was added, and degassing continued for another 5 minutes before completion. The melt was allowed to stand for 5 minutes before slag removal began. After slag removal, the melt was poured into a water-cooled copper mold, and a φ7mm×150mm cylindrical ingot was removed from the mold. After smelting, one ingot was selected for directional solidification experiments, with the cooling rate controlled at 1 kJ / s.

[0094] The ingots obtained by directional solidification are subjected to the following heat treatment process: the first stage solution temperature is 380℃ and the holding time is 4h; the second stage solution temperature is 525℃ and the holding time is 8h; the heating rate of both stages of solution is controlled at 180℃ / h, and the quenching process is adopted after the holding time is completed.

[0095] After quenching, an aging treatment was performed: the temperature was held at 175℃ for 9 hours, with the heating rate controlled at 175℃ / h. After cooling, samples were taken from the ingot for microstructure observation.

[0096] The room temperature microstructure of the alloy prepared in this embodiment is as follows: Figure 3As shown in a and 3b, the statistical results of microstructure are shown in Table 2.

[0097] Example 5

[0098] The content of each element in the cast aluminum alloy by mass percentage is shown in Table 1 below, with the balance being Al and other unavoidable impurities other than Fe.

[0099] The specific smelting steps of the alloy in this embodiment include:

[0100] A356 alloy ingots, pure Cu, and metallic silicon were placed in a melting furnace at a temperature of 770°C. After the raw materials melted, Al-10Mn, Al-10Cr, Al-10Ni, Al-10Fe, and Al-10Sb master alloys were added and melted. After complete melting, the temperature was lowered to 715°C, and pure Mg and Zn ingots wrapped in aluminum foil were added. The mixture was manually stirred for 5 minutes to ensure homogeneity, and then allowed to stand for further heating to prepare for degassing. When the melt temperature reached 745°C, a general-purpose refining agent (chloride refining agent, DURSALIT R LM 14 F Granules) was added externally to the alloy melt using a rotary argon injection method for refining and slag removal. The amount of refining agent added was 1.5 wt.‰ of the alloy melt weight.

[0101] To reduce Sr loss during degassing, after 5 minutes of degassing, 0.15 wt.% of dried Al-10Sr modifier was added to the melt. After 15 minutes of degassing, another 0.15 wt.% of dried Al-10Sr modifier was added. After 25 minutes of degassing, 0.3 wt.% of dried Al-5Ti-B refining agent was added, and degassing continued for another 5 minutes before completion. The melt was allowed to stand for 5 minutes before slag removal began. After slag removal, the melt was poured into a water-cooled copper mold, and a φ7mm×150mm cylindrical ingot was removed from the mold. After smelting, one ingot was selected for directional solidification experiments, with the cooling rate controlled at 5 kJ / s.

[0102] The ingots obtained by directional solidification are subjected to the following heat treatment process: the first stage solution temperature is 400℃ and the holding time is 7h; the second stage solution temperature is 530℃ and the holding time is 7h; the heating rate of both stages of solution is controlled at 170℃ / h, and the quenching process is adopted after the holding time is completed.

[0103] After quenching, an aging treatment was performed: the temperature was held at 185℃ for 7 hours, with the heating rate controlled at 165℃ / h. After cooling, samples were taken from the ingot for microstructure observation.

[0104] The room temperature microstructure of the alloy prepared in this embodiment is as follows: Figure 3 As shown in c and 3d, the statistical results of the microstructure are shown in Table 2.

[0105] Comparative Example 1

[0106] The content of each element in the cast aluminum alloy by mass percentage is shown in Table 1 below, with the balance being Al and other unavoidable impurities other than Fe.

[0107] The specific smelting steps for this comparative alloy include:

[0108] A356 alloy ingots, pure Cu, and metallic silicon were placed in a melting furnace at a temperature of 775°C. After the raw materials melted, Al-10Mn, Al-10Cr, Al-10Ni, and Al-10Fe master alloys were added and melted. After complete melting, the temperature was lowered to 725°C, and pure Mg and Zn ingots wrapped in aluminum foil were added. The mixture was manually stirred for 5 minutes to ensure homogeneity, and then allowed to stand for further heating to prepare for degassing. When the melt temperature reached 740°C, a general-purpose refining agent (chloride refining agent, DURSALIT R LM 14 F Granules) was added externally to the alloy melt using a rotary argon injection method for refining and slag removal. The amount of refining agent added was 1.5 wt.‰ of the alloy melt weight.

[0109] To reduce Sr loss during degassing, after 5 minutes of degassing, 0.15 wt.% of dried Al-10Sr modifier was added to the melt. After 15 minutes of degassing, another 0.15 wt.% of dried Al-10Sr modifier was added. After 25 minutes of degassing, 0.3 wt.% of dried Al-5Ti-B refining agent was added, and degassing continued for another 5 minutes before completion. The melt was allowed to stand for 5 minutes before slag removal began. After slag removal, the melt was poured into a water-cooled copper mold, and a φ7mm×150mm cylindrical ingot was removed from the mold. After smelting, one ingot was selected for directional solidification experiments, with the cooling rate controlled at 3.5 kJ / s.

[0110] The ingots obtained by directional solidification were subjected to the following heat treatment process: aging treatment: held at 190℃ for 1 hour, with a heating rate controlled at 50℃ / h. After cooling, samples were taken from the ingots for microstructure observation.

[0111] The room temperature microstructure of the alloy prepared in this comparative example is as follows: Figure 4 As shown in Table 2, the statistical results of the microstructure are presented.

[0112] Comparative Example 2

[0113] The content of each element in the cast aluminum alloy by mass percentage is shown in Table 1 below, with the balance being Al and other unavoidable impurities other than Fe.

[0114] The specific smelting steps for this comparative alloy include:

[0115] A356 alloy ingots, pure Cu, and metallic silicon were placed in a melting furnace at a temperature of 780°C. After the raw materials melted, Al-10Mn, Al-10Cr, Al-10Ni, and Al-10Fe master alloys were added and melted. After complete melting, the temperature was lowered to 725°C, and pure Mg and Zn ingots wrapped in aluminum foil were added. The mixture was manually stirred for 5 minutes to ensure homogeneity, and then allowed to stand for further heating to prepare for degassing. When the melt temperature reached 740°C, a general-purpose refining agent (chloride refining agent, DURSALIT R LM 14 F Granules) was added externally to the alloy melt using a rotary argon injection method for refining and slag removal. The amount of refining agent added was 1.5 wt.‰ of the alloy melt weight.

[0116] The degassing process was as follows: After degassing for 5 minutes, 0.15 wt.% of dried Al-10Sr modifier was added to the melt. After degassing for 15 minutes, another 0.15 wt.% of dried Al-10Sr modifier was added. After degassing for 25 minutes, 0.3 wt.% of dried Al-5Ti-B refining agent was added. Degassing continued for another 5 minutes, after which the degassing process was completed. After the melt was allowed to stand for 5 minutes, slag removal began. After slag removal, the melt was poured into a water-cooled copper mold, and a cylindrical ingot with a diameter of 7 mm × 150 mm was removed from the water-cooled copper mold ingot. After smelting, one ingot was selected for a directional solidification experiment, with the cooling rate controlled at 0.5 kJ / s.

[0117] The ingots obtained by directional solidification were subjected to the following heat treatment process: aging treatment: held at 200℃ for 30 min, with a heating rate controlled at 100℃ / h. After cooling, samples were taken from the ingots for microstructure observation.

[0118] The room temperature microstructure of the alloy prepared in this comparative example is as follows: Figure 5 As shown in Table 2, the statistical results of the microstructure are presented.

[0119] Table 1. Chemical composition and cooling rate of recycled aluminum alloys in each embodiment and comparative example.

[0120]

[0121] Table 2. Statistical results of iron-rich phases in recycled aluminum alloys in each embodiment and comparative example.

[0122]

[0123] Figure 6The contour plot shows the relationship between the Fe / Mn ratio, cooling rate, and the average SF value of the 20 largest iron-rich phases in the alloy. This invention uses an interpolation method based on experimental data to create this contour plot. Within the parameter space defined by the Fe / Mn ratio (0.5-3.5) and cooling rate (1-20 k / s), the different colors filled in the contour plot, i.e., the shape factor values, visually represent the "process control window" of this invention. Regions with high shape factors clearly constitute the preferred process window of this invention.

[0124] Referring to Tables 1 and 2, at a cooling rate of 20 k / s, the iron-rich phase morphology in Example 1 (Fe / Mn ratio 0.55) is granular; in Example 2 (Fe / Mn ratio 2.35), the iron-rich phase morphology is granular and short needle-like; and in Example 3 (Fe / Mn ratio 3.04), the iron-rich phase morphology is granular and long needle-like. At a cooling rate of 1 k / s and an Fe / Mn ratio of 1.04, the iron-rich phase morphology in Example 4 is granular and short needle-like. At a cooling rate of 5 k / s and an Fe / Mn ratio of 1.26, the iron-rich phase morphology in Example 5 is granular and short needle-like. Comparing Comparative Example 1, with an Fe / Mn ratio exceeding 3.5, and Comparative Example 2, with an Fe / Mn ratio less than 0.5, the iron-rich phase morphology in Comparative Example 1 is shaped like Chinese characters, while the iron-rich phase morphology in Comparative Example 2 is blocky. This demonstrates that by adjusting the cooling rate and the Fe / Mn ratio, the morphology of the iron-rich phase in the alloy can be controlled, thereby optimizing the alloy performance.

[0125] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from the spirit or essential characteristics of this disclosure. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this disclosure.

[0126] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for controlling the morphological characteristics of iron-rich phases in recycled aluminum alloys, characterized in that, The control method includes at least: The raw materials are cast into ingots using a directional solidification method; in the directional solidification method, the cooling rate is 1 k / s-20 k / s; in the chemical composition of the recycled aluminum alloy, the mass ratio of Fe to Mn is less than or equal to 3.5; The ingot is heat-treated.

2. The method for controlling the morphological characteristics of iron-rich phases in recycled aluminum alloys according to claim 1, characterized in that, In the chemical composition of the recycled aluminum alloy, the mass ratio of Fe to Mn is 0.5-3.

5.

3. The method for controlling the morphological characteristics of the iron-rich phase in recycled aluminum alloys according to claim 1, characterized in that, The mass ratio of Fe to Mn is 0.5-3.5, and the cooling rate is 1k / s-2k / s; The shape factor SF of the iron-rich phase in the recycled aluminum alloy satisfies: SF = 0.43-0.09 (Fe / Mn).

4. The method for controlling the morphological characteristics of the iron-rich phase in recycled aluminum alloys according to claim 1, characterized in that, The mass ratio of Fe to Mn is 0.5-3.5, and the cooling rate is 5k / s-6k / s; The shape factor SF of the iron-rich phase in the recycled aluminum alloy satisfies: SF = 0.46-0.08 (Fe / Mn).

5. The method for controlling the morphological characteristics of the iron-rich phase in recycled aluminum alloys according to claim 1, characterized in that, The mass ratio of Fe to Mn is 0.5-3.5, and the cooling rate is 18k / s-20k / s; The shape factor SF of the iron-rich phase in the recycled aluminum alloy satisfies: SF = 0.74-0.17 (Fe / Mn).

6. The method for controlling the morphological characteristics of iron-rich phases in recycled aluminum alloys according to claim 1, characterized in that, The heat treatment includes solution treatment and aging treatment.

7. The method for controlling the morphological characteristics of the iron-rich phase in recycled aluminum alloys according to claim 6, characterized in that, The solution treatment includes a first-stage solution treatment and a second-stage solution treatment. The conditions for the first-stage solution treatment are: temperature 300℃-400℃, time 4h-8h; the conditions for the second-stage solution treatment are: temperature 515℃-535℃, time 5h-10h. The heating rate in the first-stage solution treatment and / or the second-stage solution treatment is 160℃ / h-180℃ / h.

8. The method for controlling the morphological characteristics of the iron-rich phase in recycled aluminum alloys according to claim 6, characterized in that, The aging treatment conditions are: temperature 170℃-200℃, time 6h-10h; and / or, In the aging process, the heating rate is 160℃ / h-180℃ / h.

9. The method for controlling the morphological characteristics of the iron-rich phase in recycled aluminum alloys according to claim 1, characterized in that, The chemical composition of the recycled aluminum alloy, by mass percentage, includes: Si 6-7 wt.%, Cu 0.4-0.6 wt.%, Mg 0.3-0.5 wt.%, Zn 0.25-0.35 wt.%, Mn 0.15-0.25 wt.%, Cr 0.05-0.15 wt.%, Sr 150-200 ppm, Fe 0-0.7 wt.%, trace element X1, trace element X2, with the balance being Al and unavoidable impurities; Wherein, the trace element X1 is at least one of Te and B, and the content of either Te or B is 0-300 ppm; The trace element X2 is at least one of Sb and Be, and the content of either Sb or Be is 0-200 ppm.

10. The method for controlling the morphological characteristics of the iron-rich phase in recycled aluminum alloys according to claim 9, characterized in that, The Te content and B content are both 100-300 ppm; and / or, The content of either Sb or Be is 100-200 ppm.

11. The method for controlling the morphological characteristics of the iron-rich phase in recycled aluminum alloys according to claim 1, characterized in that, The iron-rich phase morphology includes at least one of granular, short needle-like, and long needle-like shapes.

12. The application of the method for controlling the morphological characteristics of the iron-rich phase in recycled aluminum alloys according to any one of claims 1-11 in the preparation of recycled aluminum alloys.

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