Corrosion-resistant 5-series aluminum alloy and preparation method thereof

Abstract

The invention discloses a corrosion-resistant 5-series aluminum alloy and a preparation method thereof, and the preparation method comprises the following steps: smelting and casting: burdening, smelting, refining and casting according to the composition to obtain a cast ingot; multi-stage homogenization treatment is conducted, specifically, the cast ingot is subjected to first-stage homogenization and second-stage homogenization in sequence; cooling the cast ingot to room temperature after homogenization treatment; hot extrusion and on-line quenching: heating the cast ingot, and carrying out hot extrusion; after a product subjected to extrusion forming is taken out of the mold, on-line forced cooling is immediately carried out, so that the product is cooled; stretching and straightening the cooled product; according to the method, alloy components are optimized, particularly the solid solution strengthening effect of Mg and Zn is controlled, Zr and Er are cooperatively added to form a nanoscale dispersed phase, meanwhile, the multi-stage homogenization and controlled cooling technology is matched to refine an as-cast structure, hot extrusion and quenching are carried out, and cold stretching and stabilizing treatment are carried out; and the material keeps good plasticity while obtaining high strength.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal material processing technology, and particularly relates to a corrosion-resistant 5-series aluminum alloy and its preparation method. Background Technology

[0002] 5-series (aluminum-magnesium) aluminum alloys, due to their low density, moderate specific strength, good formability, excellent weldability, and especially outstanding corrosion resistance, have become key materials for achieving lightweighting in aerospace, marine engineering, new energy vehicles, and rail transportation. Traditional 5-series alloys, such as 5083 and 5456, primarily achieve their basic strength through solid solution strengthening of magnesium (Mg). To meet higher performance requirements, current technological development mainly focuses on microalloying and process optimization. In composition design, the industry commonly adds appropriate amounts of transition elements such as manganese (Mn), chromium (Cr), and zirconium (Zr) to form fine, dispersed phases, which inhibit recrystallization and refine grain size. In manufacturing processes, the focus is on developing advanced technologies such as multi-stage homogenization treatment, temperature-controlled rolling or extrusion, and deformation heat treatment (TMP) to optimize the microstructure of the material and comprehensively improve its mechanical and corrosion properties. These studies and practices have significantly promoted the technological advancement of medium- and high-strength corrosion-resistant aluminum alloys.

[0003] However, despite significant advancements in existing technologies, substantial bottlenecks remain in pursuing higher overall performance indicators. First, under conventional composition systems, drastically increasing magnesium content to enhance strength often leads to increased stress corrosion sensitivity and poorer extrusion formability, making it difficult to achieve a balance between high strength (e.g., yield strength > 180 MPa), high corrosion resistance (e.g., PA-grade resistance to exfoliation corrosion), and good processability. Second, existing microalloying schemes have limited effectiveness in improving long-term environmental corrosion resistance (e.g., ultra-long-cycle salt spray corrosion) and struggle to ensure uniform microstructure and properties in extruded products with complex cross-sections. Furthermore, traditional single-stage homogenization and simple post-processing methods are insufficient in eliminating ingot compositional segregation and lack precise control over nanoscale strengthening phases, resulting in underutilization of material potential and a gap between the final product and international leading levels in terms of strength uniformity, isotropy, and long-term service stability. Therefore, developing a novel method for preparing 5-aluminum alloys with deep synergy between composition and processing to systematically address these contradictions has become a critical technological challenge urgently needing breakthroughs in this field. Summary of the Invention

[0004] In order to overcome the above-mentioned defects of the prior art, the present invention provides a corrosion-resistant 5-series aluminum alloy and its preparation method, which solves the problems of the prior art that 5-series aluminum alloys are difficult to balance high strength, high corrosion resistance and good processability, and have uneven microstructure and properties and insufficient long-term corrosion resistance.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A corrosion-resistant 5-series aluminum alloy and its preparation method, comprising, by weight percentage: Si: 0.1-0.3%, Mn: 0.5-0.7%, Mg: 5.1-5.5%, Zn: 0.3-0.5%, Ti: 0.1-0.3%, Zr: 0.3-0.5%, Er: 0.1-0.2%, Fe≤0.3%, with the balance being Al and unavoidable impurities; the aluminum alloy has a tensile strength ≥310MPa, a yield strength ≥180MPa, an elongation ≥15%, and a peeling corrosion resistance grade of PA as determined by GB / T22639 or ASTM G34 standards, and the aluminum alloy is prepared by the method described in claim 6.

[0006] Preferably, the weight percentage ratio of Mn to Zr in the composition, Mn / Zr, is 1.0-2.3.

[0007] Preferably, the aluminum alloy has an average grain size ≤50μm and a recrystallization volume fraction ≤20%.

[0008] Preferably, the intergranular corrosion mass loss of the aluminum alloy, as measured according to ASTM G67 standard, is ≤15mg / cm².

[0009] Preferably, after 3000 hours of neutral salt spray testing, the maximum corrosion depth on its surface is ≤50μm.

[0010] Preferably, a method for corrosion-resistant 5-series aluminum alloys includes the following steps: S1. Melting and casting: The ingredients are batched, melted, refined and cast according to the composition described in claim 1 to obtain an ingot; S2. Multi-stage homogenization treatment: The ingot is subjected to a first-stage homogenization and a second-stage homogenization in sequence; the conditions for the first-stage homogenization are: temperature 445-455℃, holding time 8-12 hours; the conditions for the second-stage homogenization are: temperature 465-475℃, holding time 12-16 hours; after the homogenization treatment, the ingot is cooled to room temperature at a cooling rate of 100-200℃ / hour. S3. Hot extrusion and online quenching: The ingot treated with S2 is heated to 480-490℃ and hot extruded; after the extruded product is demolded, it is immediately subjected to online forced cooling, so that the product cools to below 250℃ within 60 seconds. S4. Deformation and Stabilization Treatment: The product treated in S3 and cooled to below 50°C is stretched and straightened with a stretching rate of 2.0-2.5%; then, it is subjected to stabilization heat treatment at 100-130°C for 24-36 hours.

[0011] Preferably, in step S3, before hot extrusion, the preheating temperature of the extrusion die is 440-460°C, and the preheating temperature of the extrusion cylinder is 450-470°C.

[0012] Preferably, in step S3, the extrusion speed of the hot extrusion is 1.0-1.5 m / min.

[0013] Preferably, in step S2, the cooling is performed using forced air cooling or mist cooling.

[0014] Preferably, in step S1, the Zr is added in the form of an Al-Zr master alloy, the Er is added in the form of an Al-Er master alloy, and the master alloy is added at a melt temperature of 720-750°C.

[0015] The technical effects and advantages of the corrosion-resistant 5-series aluminum alloy and its preparation method of the present invention are as follows: 1. This invention optimizes the alloy composition, particularly controlling the solid solution strengthening effect of Mg and Zn, and synergistically adds Zr and Er to form a nanoscale dispersed phase. Simultaneously, it employs multi-stage homogenization and controlled cooling processes to refine the as-cast microstructure, hot extrusion and online quenching to achieve fine-grain strengthening and solid solution strengthening, and cold stretching and stabilization treatments to regulate dislocation structure and atomic segregation. This allows the material to achieve high strength while maintaining good plasticity. Tensile strength can reach over 310 MPa, yield strength over 180 MPa, and elongation over 15%. Furthermore, a specific stretching and straightening process effectively improves the anisotropy of the sheet metal, enhancing the uniformity of material properties in different directions.

[0016] 2. The alloy composition design of this invention, through strict control of the Fe and Si impurities and the addition of appropriate amounts of Mn, Zr, and Er elements, effectively inhibits the formation of harmful cathodic phases and continuous anodic phases. Combined with optimized homogenization and heat treatment processes, it promotes a microstructure with uniform corrosion potential. This results in the material not only achieving the highest PA level of resistance to exfoliation corrosion but also exhibiting extremely low intergranular corrosion sensitivity. More importantly, it demonstrates excellent long-term environmental corrosion resistance; in a stringent 3000-hour neutral salt spray test, the corrosion depth was effectively controlled to an extremely low level, meeting the stringent requirements of high-end equipment for long-term reliability.

[0017] 3. The invention's rational composition design, especially the combination of Mg content with elements such as Zn and Mn, optimizes the alloy's high-temperature rheological properties while ensuring strength. Combined with precise extrusion temperature and speed control, this alloy is suitable for extrusion production of profiles or tubes with relatively complex cross-sections, expanding its application range in the field of high-performance structural components.

[0018] 4. This invention, through the coordinated control of the entire process of "composition design - homogenization - thermal processing - post-treatment," ensures that the final product obtains a uniform, fine-grained structure (average grain size ≤ 50 μm) and a low-dislocation subcrystalline structure, and effectively suppresses incomplete recrystallization. This stable microstructure is the fundamental guarantee for the material to have both high comprehensive performance and good service stability. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the preparation process of a corrosion-resistant 5-series aluminum alloy and its preparation method, as proposed in this invention. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include," "contain," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "includes..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0022] refer to Figure 1This invention provides a corrosion-resistant 5-series aluminum alloy and its preparation method. The aluminum alloy, by weight percentage, comprises: Si 0.1-0.3%, Mn 0.5-0.7%, Mg 5.1-5.5%, Zn 0.3-0.5%, Ti 0.1-0.3%, Zr 0.3-0.5%, Er 0.1-0.2%, Fe ≤ 0.3%, with the balance being Al and unavoidable impurities. Preferably, the weight ratio of Mn to Zr is 1.0-2.3. The preparation method includes: melting and casting ingots according to the composition; performing two-stage homogenization treatment on the ingots and controlling the cooling rate; hot extruding the ingots after heating and subjecting the extruded product to online forced cooling; and finally, cold stretching and straightening and low-temperature stabilization heat treatment on the product. This invention utilizes a specific microalloying composition system in conjunction with a complete set of processes including multi-stage homogenization, online quenching, and post-deformation stabilization treatment to produce aluminum alloys that possess high strength, high elongation, and excellent overall corrosion resistance, making them particularly suitable for fields such as shipbuilding where the comprehensive performance requirements of materials are stringent. Example 1

[0023] This embodiment provides a corrosion-resistant 5-series aluminum alloy and its preparation method for typical composition and process verification. Specific implementation details include: Purpose of implementation: This demonstrates the comprehensive performance of the aluminum alloy prepared by combining the median of the composition range of this invention with the core process.

[0024] Implementation ingredients: The alloy composition, by weight percentage, is: Si: 0.15%, Mn: 0.60%, Mg: 5.3%, Zn: 0.40%, Ti: 0.15%, Zr: 0.40%, Er: 0.15%, Fe: 0.15%, with the balance being Al and unavoidable impurities. The weight percentage ratio of Mn to Zr is 1.50.

[0025] Implementation steps: S1 Melting and Casting: High-purity aluminum and magnesium ingots, along with appropriate intermediate alloys, are used. The mixture is heated to 750°C in a melting furnace and stirred, followed by argon rotary blowing refining. After refining, it is cast into Φ200mm round ingots at 720°C.

[0026] S2 Multi-stage Homogenization Treatment: The ingot is placed in a homogenizing furnace, first heated to 450℃ and held for 10 hours, then heated to 470℃ and held for another 14 hours. After the treatment, the ingot is immediately removed and cooled to room temperature by forced air cooling at a rate of approximately 150℃ / hour.

[0027] S3 Hot Extrusion and Online Quenching: After the ingot is rolled into a sheet, it is heated to 485°C in an induction furnace. Simultaneously, the extrusion die is preheated to 450°C, and the extrusion cylinder to 460°C. The ingot is extruded into a 6mm thick sheet on a 600-ton extruder at a speed of 1.2m / min. After demolding, the sheet immediately enters a high-pressure air-cooling quenching system to ensure its temperature drops below 250°C within 50 seconds.

[0028] S4 Deformation and Stabilization Treatment: After the extruded sheet is left to stand at room temperature for 24 hours, it is tension straightened to control its elongation rate at 2.3%. Subsequently, the sheet is placed in an air-circulating oven and kept at 120°C for 30 hours for stabilization treatment. After completion, it is air-cooled to room temperature. Implementation effect

[0029] The obtained sheet material was tested, and the results are as follows: tensile strength was 325 MPa, yield strength was 192 MPa, and elongation was 16.5%. The exfoliation corrosion test (according to ASTM G34) was rated PA. The intergranular corrosion test (according to ASTM G67) showed a mass loss of 10.2 mg / cm². After 3000 hours of neutral salt spray testing (according to GB / T10125), the maximum surface corrosion depth was 35 μm. Electrochemical microstructure analysis (EBSD) showed an average grain size of 42 μm and a recrystallization volume fraction of approximately 15%. Example 2

[0030] This embodiment provides a corrosion-resistant 5-series aluminum alloy and its preparation method, used to verify the effects of high Mn and Mg content and high homogenization temperature. Specific implementation details include: Purpose of implementation: This explains the effect on alloy properties when the Mn and Mg contents are high and the upper limit of the homogenization stage temperature is used.

[0031] Implementation ingredients: Si: 0.25%, Mn: 0.65%, Mg: 5.4%, Zn: 0.35%, Ti: 0.25%, Zr: 0.35%, Er: 0.10%, Fe: 0.18%, Mn / Zr ratio is 1.86.

[0032] Implementation steps: The smelting and casting steps are the same as in Example 1. Homogenization treatment: First stage: 455℃ for 8 hours; Second stage: 475℃ for 12 hours; followed by mist cooling (rate approximately 200℃ / h). Extrusion quenching: Ingot temperature 490℃, die temperature 445℃, extrusion cylinder temperature 455℃, extrusion speed 1.0 m / min; forced cooling to below 250℃ within 55 seconds after demolding. Post-treatment: 2.0% elongation, followed by stabilization heat treatment at 110℃ for 36 hours. Implementation effect

[0033] Performance test results: Tensile strength 318 MPa, yield strength 188 MPa, elongation 17.0%. Exfoliation corrosion rating PA, intergranular corrosion mass loss 11.5 mg / cm². Maximum salt spray corrosion depth 42 μm after 3000 hours. Average grain size 45 μm, recrystallization fraction 18%. Example 3

[0034] This embodiment provides a corrosion-resistant 5-series aluminum alloy and its preparation method, used to verify the effect of extending the homogenization time while keeping the Mg and Zr contents close to the lower limit. Specific implementation details include: Purpose of implementation: This explains the microstructure and properties of the alloy when the Mg and Zr contents are close to the lower limit, but the homogenization time is relatively long.

[0035] Implementation ingredients: Si: 0.10%, Mn: 0.55%, Mg: 5.2%, Zn: 0.45%, Ti: 0.20%, Zr: 0.45%, Er: 0.12%, Fe: 0.12%, Mn / Zr ratio is 1.22.

[0036] Implementation steps: The smelting and casting steps are the same as in Example 1. Homogenization treatment: First stage: holding at 445℃ for 12 hours; second stage: holding at 465℃ for 16 hours, followed by forced air cooling (rate approximately 100℃ / h). Extrusion quenching: Ingot temperature 480℃, die temperature 455℃, extrusion cylinder temperature 465℃, extrusion speed 1.5m / min, forced cooling to below 250℃ within 45 seconds after demolding. Post-treatment: Elongation rate 2.5%, followed by stabilization heat treatment at 130℃ for 24 hours. Implementation effect

[0037] Performance test results: Tensile strength 332 MPa, yield strength 195 MPa, elongation 15.8%. Exfoliation corrosion rating PA, intergranular corrosion mass loss 9.8 mg / cm². Maximum salt spray corrosion depth 38 μm after 3000 hours. Average grain size 40 μm, recrystallization fraction 12%. Example 4

[0038] This embodiment provides a corrosion-resistant 5-series aluminum alloy and its preparation method, used to verify the contribution of Er element content close to the upper limit to corrosion resistance. Specific implementation details include: Purpose of implementation: This indicates the impact of Er content near its upper limit on the corrosion resistance of the alloy when combined with moderate process parameters.

[0039] Implementation ingredients: Si: 0.20%, Mn: 0.58%, Mg: 5.5%, Zn: 0.30%, Ti: 0.10%, Zr: 0.30%, Er: 0.18%, Fe: 0.20%, Mn / Zr ratio is 1.93.

[0040] Implementation steps: The smelting and casting steps are the same as in Example 1. Homogenization treatment: First stage: 450℃ for 9 hours; Second stage: 470℃ for 15 hours, followed by forced air cooling (rate approximately 180℃ / h). Extrusion quenching: Ingot temperature 485℃, die temperature 460℃, extrusion cylinder temperature 470℃, extrusion speed 1.3m / min, forced cooling to below 250℃ within 60 seconds after demolding. Post-treatment: Elongation rate 2.2%, followed by stabilization heat treatment at 105℃ for 28 hours. Implementation effect

[0041] Performance test results: Tensile strength 312 MPa, yield strength 185 MPa, elongation 18.2%. Exfoliation corrosion rating PA, intergranular corrosion mass loss 13.0 mg / cm². Maximum salt spray corrosion depth 46 μm after 3000 hours. Average grain size 48 μm, recrystallization fraction 20%. Example 5

[0042] This embodiment provides a corrosion-resistant 5-series aluminum alloy and its preparation method, used to verify the process adaptability when all major elements are close to their upper limits. Specific implementation details include: Purpose of implementation: This explains the process adaptability and final performance of the alloy when the content of each major element is close to the upper limit.

[0043] Implementation ingredients: Si: 0.30%, Mn: 0.70%, Mg: 5.1%, Zn: 0.50%, Ti: 0.30%, Zr: 0.50%, Er: 0.20%, Fe: 0.25%, Mn / Zr ratio is 1.40.

[0044] Implementation steps: The melting and casting steps are the same as in Example 1. Homogenization treatment: First stage: holding at 450℃ for 11 hours; second stage: holding at 470℃ for 13 hours, followed by mist cooling (rate approximately 120℃ / h). Extrusion quenching: Ingot temperature 488℃, die temperature 450℃, extrusion cylinder temperature 458℃, extrusion speed 1.1m / min, forced cooling to below 250℃ within 58 seconds after demolding. Post-treatment: Elongation rate 2.4%, followed by stabilization heat treatment at 125℃ for 26 hours. Implementation effect

[0045] Performance test results: Tensile strength 328 MPa, yield strength 190 MPa, elongation 16.0%. Exfoliation corrosion rating PA, intergranular corrosion mass loss 10.5 mg / cm². Maximum salt spray corrosion depth 40 μm after 3000 hours. Average grain size 43 μm, recrystallization fraction 16%.

[0046] Comparative Example A This comparative example provides a comparison of traditional ingredients, using conventional ingredients in conjunction with the process of this invention to demonstrate the necessity of the ingredients. Specific details include: Purpose of implementation: The conventional Al-Mg alloy composition was used, but the performance differences were investigated by attempting to use the process of this invention.

[0047] Implementation ingredients (traditional ingredients): Si: 0.15%, Mn: 0.60%, Mg: 4.5%, Zn: 0.40%, Ti: 0.15%, Zr: 0.10%, Er: 0%, Fe: 0.15%, balance Al. Mn / Zr ratio is 6.0.

[0048] Implementation steps: The preparation process is exactly the same as in Example 1, including multi-stage homogenization, online forced cooling, stretching and straightening, and stabilization heat treatment. Implementation effect

[0049] Performance test results: tensile strength 285 MPa, yield strength 158 MPa, elongation 13.5%. Exfoliation corrosion rating: PC grade. Intergranular corrosion mass loss: 25.8 mg / cm². After 3000 hours of salt spray testing, the maximum corrosion depth was 105 μm. Average grain size: 78 μm, recrystallization fraction: approximately 60%. Despite employing the complete process of this invention, due to insufficient Mg and Zr content and absence of Er, the strength, plasticity, and all corrosion resistance properties are far from reaching the levels of Examples 1-5.

[0050] Comparative Example B This comparative example provides a simplified process comparison, using the components of this invention in conjunction with conventional processes to demonstrate the necessity of the process. Specific details include: Purpose of implementation: The performance differences were examined by using the components of this invention but employing a simplified traditional process.

[0051] Implementation ingredients: Same components as in Example 1.

[0052] Implementation steps (traditional method): S1 Smelting and Casting: Same as Example 1.

[0053] S2 single-stage homogenization treatment: After holding the ingot at 470℃ for 10 hours, it is directly taken out of the furnace and naturally cooled to room temperature.

[0054] S3 Hot Extrusion and Air Cooling: The ingot is heated to 485°C for extrusion, and the preheating temperature of the die and extrusion cylinder is the same as in Example 1. However, after the product is demolded, it is placed in the air to cool naturally, and the time required to cool to below 250°C exceeds 180 seconds.

[0055] S4 Simple Straightening: Straightens the cooled sheet material with an elongation of approximately 1.0%. No stabilization heat treatment is performed. Implementation effect

[0056] Performance test results: tensile strength 298 MPa, yield strength 168 MPa, elongation 14.0%. Exfoliation corrosion rating: PB. Intergranular corrosion mass loss: 19.5 mg / cm². After 3000 hours of salt spray testing, the maximum corrosion depth was 88 μm. Average grain size: 68 μm, recrystallization fraction: approximately 45%. Although the composition is the same as Example 1, due to the absence of the multi-stage homogenization, online forced quenching, and complete post-treatment process of this invention, its performance, especially corrosion resistance and yield strength, is significantly lower than that of Example 1.

[0057] Overall effect analysis: The test results of Examples 1 to 5 show that by using the composition range specified in this invention (including specific contents of Mg, Zn, Zr, and Er, and controlling the Mn / Zr ratio to be between 1.0 and 2.3) and the complete set of preparation processes (multi-stage homogenization and controlled cooling, hot extrusion and online quenching, and cold stretching stabilization treatment), aluminum alloys with excellent comprehensive performance can be stably prepared. All products in the embodiments simultaneously meet the following performance indicators: tensile strength between 312 and 332 MPa (all ≥310 MPa), yield strength between 185 and 195 MPa (all ≥180 MPa), elongation between 15.8% and 18.2% (all ≥15%); exfoliation corrosion level reaching PA grade; intergranular corrosion mass loss between 9.8 and 13.0 mg / cm² (all ≤15 mg / cm²); 3000-hour salt spray corrosion depth between 35 and 46 μm (all ≤50 μm); and average grain size between 40 and 48 μm (all ≤50 μm).

[0058] The results of Comparative Example A demonstrate that even when the process of this invention is fully adopted, if the alloy composition does not meet the requirements (insufficient Mg content, excessively low Zr content, and absence of Er), the high strength and high corrosion resistance desired by this invention cannot be obtained. Its tensile strength (285 MPa), yield strength (158 MPa), elongation (13.5%), and all corrosion resistance properties (PC grade exfoliation corrosion, 25.8 mg / cm² intergranular corrosion loss, and 105 μm salt spray depth) are significantly inferior to those of the examples, highlighting the necessity of the specific component combination of this invention.

[0059] The results of Comparative Example B demonstrate that even when using the components of this invention, if key steps such as multi-stage homogenization and controlled cooling, online quenching, and sufficient stabilization treatment are omitted from the process, the product's performance will significantly decrease. Its tensile strength (298 MPa), yield strength (168 MPa), elongation (14.0%), and corrosion resistance (exfoliation corrosion grade PB, intergranular corrosion loss 19.5 mg / cm², salt spray depth 88 μm) all fall short of the levels of this invention, highlighting the necessity of the specific process combination of this invention.

[0060] In summary, this invention achieves a significant and balanced improvement in the strength, plasticity, and corrosion resistance of aluminum alloys through the synergistic effect of a specific component system and a matching complete set of processing techniques. Its technical effectiveness stems from the precise and inseparable interaction between the components and the process.

[0061] Compared with Examples 1-5 and Comparative Examples A and B, this invention, through a systematic comparison of five examples (Examples 1-5) and two targeted comparative examples (Comparative Example A and Comparative Example B), fully verifies the necessity and superiority of the synergistic effect of a specific component system and a complete preparation process in obtaining high-performance corrosion-resistant 5-series aluminum alloys. The core comparative conclusions are summarized as follows: The consistency of Examples 1-5 proves that the solution of the present invention is stable and reliable, and its overall performance comprehensively surpasses conventional standards. All embodiments strictly adhered to the composition range specified in this invention (Mg 5.1-5.5%, Zr 0.3-0.5%, Er 0.1-0.2%, and Mn / Zr ratio controlled between 1.0 and 2.3) and the complete preparation process (multi-stage homogenization + controlled cooling, hot extrusion + online quenching, cold stretching + stabilization treatment). Although specific parameters fluctuated within permissible ranges, the final product performance exhibited high consistency and stability. In terms of mechanical properties, the tensile strength is stable in the range of 312-332 MPa, the yield strength is in the range of 185-195 MPa, and the elongation is maintained above 15.8%, fully meeting and exceeding the high standard of "tensile strength ≥310 MPa, yield strength ≥180 MPa, elongation ≥15%".

[0062] In terms of corrosion resistance, it exhibits comprehensive and outstanding corrosion resistance. The exfoliation corrosion rating of all embodiments reaches the highest PA level; the mass loss due to intergranular corrosion is less than 15 mg / cm² (between 9.8 and 13.0 mg / cm²); in particular, in the 3000-hour neutral salt spray test simulating harsh environments, the maximum corrosion depth was strictly controlled within 50 μm (35-46 μm), demonstrating its excellent long-term service reliability.

[0063] In terms of microstructure, all samples exhibited uniform and fine grain structures with an average grain size between 40 and 48 μm and a low recrystallization fraction (12-20%), which is the microscopic basis for achieving the aforementioned excellent comprehensive performance.

[0064] Comparative Example A (variable component) and Comparative Example B (variable process) demonstrate, from the opposite perspective, the indispensability of the core elements of this invention. Comparative Example A (using conventional components and the process of this invention): Although the same advanced preparation process as Example 1 was used, its properties declined significantly across the board due to insufficient Mg content (4.5%) and Zr content (0.1%), and the absence of Er element. Its strength (yield strength 158 MPa) and plasticity (elongation 13.5%) were far below standard; corrosion resistance was severely deteriorated (exfoliation corrosion PC grade, intergranular corrosion loss 25.8 mg / cm², salt spray depth 105 μm); and the microstructure was also significantly coarsened (average grain size 78 μm). This result irrefutably proves that, without the specific high Mg, appropriate Zr, and Er-added microalloying composition system of this invention, even with the most advanced processes, it is impossible to achieve the high strength and high corrosion resistance performance achieved by this invention. This highlights the crucial role of the composition design in this invention.

[0065] Comparative Example B (using the components of this invention, but performing a simplified traditional process): Although the same optimized components as in Example 1 were used, the process reverted to the traditional single-stage homogenization, natural cooling extrusion, and omitting the stabilization treatment. The results were significantly lower than in Example 1: strength (especially yield strength reduced to 168 MPa) and elongation (14.0%) decreased; corrosion resistance was significantly reduced (exfoliation corrosion decreased to PB level, intergranular corrosion loss 19.5 mg / cm², salt spray depth 88 μm); and microstructure uniformity and fineness also deteriorated (average grain size 68 μm). These results clearly demonstrate that even with optimized components, without the synergistic effect of the multi-stage homogenization controlled cooling, online quenching, and post-deformation stabilization processes of this invention, the material's performance potential cannot be fully realized, and the superior comprehensive performance expected by this invention cannot be achieved. This highlights the crucial role of the complete process system of this invention.

[0066] The evidence from both positive and negative perspectives demonstrates that this invention is not a simple improvement or addition of existing components or processes. The success of Examples 1-5, in stark contrast to the failures of Comparative Examples A and B, conclusively proves the inseparable and profound synergistic effect between the "specific component range (especially the addition of high Mg, Zr, and Er and control of the Mn / Zr ratio)" and the "specific complete preparation process (multi-stage homogenization controlled cooling, online strong quenching, and cold stretching stabilization)" proposed in this invention. It is precisely this precise matching and synergistic effect of components and processes that successfully solves the industry problems of mutual constraints between strength and corrosion resistance, insufficient long-term corrosion resistance, and uneven microstructure and properties in traditional 5-series aluminum alloys, ultimately achieving a unity of high strength, high plasticity, comprehensive excellent corrosion resistance, and good machinability. The technical effects of this invention have outstanding substantive characteristics and significant progress.

[0067] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of protection of the claims.

[0068] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A corrosion resistant 5xxx aluminum alloy characterized by, The composition comprises, by weight percentage: Si: 0.1-0.3%, Mn: 0.5-0.7%, Mg: 5.1-5.5%, Zn: 0.3-0.5%, Ti: 0.1-0.3%, Zr: 0.3-0.5%, Er: 0.1-0.2%, Fe≤0.3%, and the balance of Al and inevitable impurities; the tensile strength of the aluminum alloy is ≥310 MPa, the yield strength is ≥180 MPa, the elongation is ≥15%, the anti-exfoliation corrosion grade measured according to GB / T22639 or ASTM G34 standard is PA grade, and the aluminum alloy is prepared by the method of claim 6.

2. The corrosion resistant 5xxx aluminum alloy of claim 1, wherein, The weight percentage ratio of Mn to Zr in the composition is Mn / Zr = 1.0-2.

3.

3. The corrosion resistant 5xxx aluminum alloy of claim 1, wherein, The average grain size of the aluminum alloy is ≤50 μm, and the recrystallization volume fraction is ≤20%.

4. The corrosion resistant 5xxx aluminum alloy of claim 1, wherein, The intergranular corrosion mass loss of the aluminum alloy measured according to ASTM G67 standard is ≤15 mg / cm².

5. The corrosion resistant 5xxx aluminum alloy of claim 1, wherein, The maximum surface corrosion depth after 3000 hours of neutral salt spray testing is ≤50 μm.

6. A method of producing the corrosion-resistant 5-series aluminum alloy according to any one of claims 1 to 5, characterized by, The method comprises the following steps: S1, melting and casting: ingredients are prepared according to the composition of claim 1, melting, refining, and casting to obtain an ingot; S2, multi-stage homogenization treatment: the ingot is sequentially subjected to first-stage homogenization and second-stage homogenization; the first-stage homogenization is carried out at a temperature of 445-455 ℃ for 8-12 hours; the second-stage homogenization is carried out at a temperature of 465-475 ℃ for 12-16 hours; after homogenization treatment, the ingot is cooled to room temperature at a cooling rate of 100-200 ℃ / hour; S3, hot extrusion and online quenching: the ingot treated in S2 is heated to 480-490 ℃ and subjected to hot extrusion; after the extrusion forming product is discharged, it is immediately subjected to online forced cooling so that the product is cooled to below 250 ℃ within 60 seconds; S4, deformation and stabilization treatment: the product treated in S3 and cooled to below 50 ℃ is subjected to tensile straightening at a stretching rate of 2.0-2.5%; subsequently, it is subjected to stabilization heat treatment at 100-130 ℃ for 24-36 hours.

7. The method for preparing a corrosion-resistant 5-series aluminum alloy as described in claim 6, characterized in that, In step S3, before hot extrusion, the preheating temperature of the extrusion die is 440-460 ℃, and the preheating temperature of the extrusion cylinder is 450-470 ℃.

8. The method for preparing a corrosion-resistant 5-series aluminum alloy as described in claim 6, characterized in that, In step S3, the extrusion speed of the hot extrusion is 1.0-1.5 m / min.

9. The method for preparing a corrosion-resistant 5-series aluminum alloy as described in claim 6, characterized in that, In step S2, the cooling is carried out by forced air cooling or mist cooling.

10. The method for preparing a corrosion-resistant 5-series aluminum alloy as described in claim 6, characterized in that, In step S1, the Zr is added in the form of Al-Zr intermediate alloy, the Er is added in the form of Al-Er intermediate alloy, and the intermediate alloy is added when the melt temperature is 720-750 ℃.

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