Corrosion-resistant aluminum alloy and method for manufacturing the same

Abstract

This invention provides a corrosion-resistant aluminum alloy and its preparation method, belonging to the field of aluminum alloy technology. The corrosion-resistant aluminum alloy comprises the following components by mass percentage: Si 0.45~0.65%, Mg 0.85~1.15%, Mn 0.15~0.30%, Zr 0.08~0.15%, Er 0.03~0.08%, Ti 0.01~0.03%, Fe≤0.12%, Cu≤0.05%, and the balance Al; the mass ratio of Mg to Si is 1.8~2.0. This invention improves the corrosion resistance of the aluminum alloy by limiting the magnesium-silicon mass ratio and achieving a slight excess of magnesium; through composite microalloying, it achieves a synergistic effect of iron phase modification and dispersed phase pinning at low manganese content, reducing quenching sensitivity; the addition of titanium achieves grain refinement; and strict control of copper content avoids deterioration of corrosion resistance.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy technology, specifically relating to a corrosion-resistant aluminum alloy and its preparation method. Background Technology

[0002] 6-series aluminum-magnesium-silicon alloys are currently the most widely used heat-treatable and wrought aluminum alloys in the global industrial system. Utilizing the precipitation strengthening effect of the Mg2Si phase, they achieve a balanced match between hot extrusion formability, surface finish, and basic atmospheric corrosion resistance within a medium strength range. They are core structural materials in fields such as building materials, new energy equipment, rail transportation, and lightweight automobiles. With the upgrading demands of coastal infrastructure, marine engineering, and long-life outdoor equipment, the intergranular corrosion and pitting failure problems of conventional 6-series alloys in chloride-ion humid and hot environments are becoming increasingly prominent. Corrosion resistance has become a key bottleneck restricting their expansion into high-reliability scenarios, making highly corrosion-resistant 6-series alloys a key research and development direction in the field of aluminum alloy materials.

[0003] Current mainstream high corrosion-resistant 6-series alloys mainly employ low-iron, high-purity raw materials, an excess Mg chemical ratio, and the addition of manganese and chromium to transform the harmful acicular β-AlFeSi phase into a less harmful granular α phase. Zirconium and other microalloying elements are then used to refine the grains and disrupt corrosion pathways. However, the following drawbacks remain: while manganese and chromium modify the iron phase, they significantly increase the alloy's quenching sensitivity, leading to uneven corrosion resistance. Therefore, how to improve the corrosion resistance of aluminum alloys has become a pressing technical challenge in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a corrosion-resistant aluminum alloy and its preparation method. The aluminum alloy provided by this invention possesses excellent corrosion resistance.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a corrosion-resistant aluminum alloy comprising the following components by mass percentage: Si 0.45~0.65%, Mg 0.85~1.15%, Mn 0.15~0.30%, Zr 0.08~0.15%, Er 0.03~0.08%, Ti 0.01~0.03%, Fe≤0.12%, Cu≤0.05%, and the balance Al; The mass ratio of Mg to Si is 1.8 to 2.0.

[0006] Preferably, the composition comprises the following components by mass percentage: Si 0.50~0.60%, Mg 1.00~1.10%, Mn 0.20~0.25%, Zr 0.10~0.12%, Er 0.05~0.06%, Ti 0.02~0.03%, Fe≤0.10%, Cu≤0.04%, and the balance Al.

[0007] Preferably, the mass ratio of Mg to Si is 1.83 to 1.95.

[0008] The present invention also provides a method for preparing the corrosion-resistant aluminum alloy described in the above technical solution, comprising: The raw materials are mixed and then smelted and cast sequentially to obtain ingots; The ingot is subjected to homogenization annealing, hot extrusion, quenching and aging treatment in sequence to obtain a corrosion-resistant aluminum alloy.

[0009] Preferably, the casting is a semi-continuous casting, and the casting temperature is 700~730℃.

[0010] Preferably, the holding temperature for homogenization annealing is 560~580℃, the holding time for homogenization annealing is 8~12h, and the rate of heating to the homogenization annealing holding temperature is 100~150℃ / h.

[0011] Preferably, the hot extrusion temperature is 520~540℃, and the hot extrusion ratio is (25~40):1.

[0012] Preferably, the quenching is online water mist quenching, and the cooling rate of the quenching is ≥120℃ / s.

[0013] Preferably, the aging process includes a first pre-aging, a second-level grain boundary regulation aging, and a third-level stability aging performed sequentially; The holding temperature for the first pre-aging is 100~120℃, and the holding time for the first pre-aging is 2~4h; The holding temperature for the secondary grain boundary regulation aging is 160~170℃, and the holding time for the secondary grain boundary regulation aging is 1~2h. The holding temperature for the third-stage stabilization aging is 140~150℃, and the holding time for the third-stage stabilization aging is 6~8h.

[0014] Preferably, the heat preservation temperature for the first pre-aging is 110°C, and the heat preservation time for the first pre-aging is 3 hours. The holding temperature for the secondary grain boundary regulation aging is 160~165℃, and the holding time for the secondary grain boundary regulation aging is 1.5h. The holding temperature for the third-stage stabilization aging is 145~150℃, and the holding time for the third-stage stabilization aging is 7h.

[0015] This invention provides a corrosion-resistant aluminum alloy comprising the following components by mass percentage: Si 0.45~0.65%, Mg 0.85~1.15%, Mn 0.15~0.30%, Zr 0.08~0.15%, Er 0.03~0.08%, Ti 0.01~0.03%, Fe≤0.12%, Cu≤0.05%, and the balance Al; wherein the mass ratio of Mg to Si is 1.8~2.0. This invention improves the corrosion resistance of the aluminum alloy by limiting the magnesium-silicon mass ratio and achieving a slight excess of magnesium; through trace element composite microalloying, it achieves a synergistic effect of iron phase modification and dispersed phase pinning at low manganese content, reducing quenching sensitivity; the addition of titanium achieves grain refinement; and strict control of copper content avoids deterioration of corrosion resistance. Experimental results show that the aluminum alloy provided by this invention has a maximum intergranular corrosion depth ≤0.05mm after standard immersion testing, with a corrosion grade of 1~2 (pitting / mild intergranular corrosion) and no penetrating intergranular corrosion; after 1000h neutral salt spray testing, the surface pitting corrosion rating is ≥9 (GB / T 6461), and the corrosion weight loss per unit area is ≤0.5mg / cm³. 2 Under a loading stress of 75% of the yield strength, there is no tendency for stress corrosion cracking; the stress corrosion sensitivity coefficient of the slow tensile specimen is ≤0.15, and the fracture time is more than 3 times that of conventional 6061-T6. Detailed Implementation

[0016] This invention provides a corrosion-resistant aluminum alloy comprising the following components by mass percentage: Si 0.45~0.65%, Mg 0.85~1.15%, Mn 0.15~0.30%, Zr 0.08~0.15%, Er 0.03~0.08%, Ti 0.01~0.03%, Fe≤0.12%, Cu≤0.05%, and the balance Al; The mass ratio of Mg to Si is 1.8 to 2.0.

[0017] The corrosion-resistant aluminum alloy provided by this invention comprises 0.45-0.65% Si by weight. As one embodiment, the weight percentage of Si can be 0.46%, 0.47%, 0.48%, 0.49%, 0.50%, 0.51%, 0.52%, 0.53%, 0.54%, 0.55%, 0.56%, 0.57%, 0.58%, 0.59%, 0.60%, 0.61%, 0.62%, 0.63%, or 0.64%.

[0018] The corrosion-resistant aluminum alloy provided by this invention comprises 0.85-1.15% Mg by mass percentage. As one embodiment, the mass percentage of Mg can be 0.86%, 0.87%, 0.88%, 0.89%, 0.90%, 0.91%, 0.92%, 0.93%, 0.94%, 0.95%, 0.96%, 0.97%, 0.98%, 0.99%, 1.00%, 1.01%, 1.02%, 1.03%, 1.04%, 1.05%, 1.06%, 1.07%, 1.08%, 1.09%, 1.10%, 1.11%, 1.12%, 1.13%, or 1.14%. The slight excess of magnesium in this invention can improve the corrosion resistance of the aluminum alloy.

[0019] In this invention, the mass ratio of Mg to Si is 1.8 to 2.0. As one embodiment, the mass ratio of Mg to Si can be 1.83, 1.85, 1.86, 1.88, 1.90, 1.92, 1.94, 1.95, 1.96, or 1.98. Limiting the mass ratio of Mg to Si within the above range further improves the corrosion resistance of the aluminum alloy.

[0020] The corrosion-resistant aluminum alloy provided by this invention comprises 0.15-0.30% Mn by mass percentage. As one embodiment, the mass percentage of Mn can be 0.16%, 0.17%, 0.18%, 0.19%, 0.20%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, or 0.29%. This invention avoids excessive quenching sensitivity by employing a low-manganese modified iron phase.

[0021] The corrosion-resistant aluminum alloy provided by this invention comprises 0.08-0.15% Zr by mass percentage. As one embodiment, the mass percentage of Zr can be 0.09%, 0.10%, 0.11%, 0.12%, 0.13%, or 0.14%. In this invention, the Zr and Er combine to form a dispersed phase, pinning grain boundaries and reducing quenching sensitivity.

[0022] The corrosion-resistant aluminum alloy provided by this invention comprises 0.03-0.08% Er by mass percentage. As one embodiment, the mass percentage of Er can be 0.04%, 0.05%, 0.06%, or 0.07%. In this invention, Er and Zr combine to form a dispersed phase, pinning grain boundaries and reducing quenching sensitivity.

[0023] The corrosion-resistant aluminum alloy provided by this invention comprises 0.01-0.03% Ti by mass percentage. As one embodiment, the mass percentage of Ti can be 0.02%. In this invention, the Ti can refine the grain size.

[0024] The corrosion-resistant aluminum alloy provided by this invention comprises ≤0.12% Fe by mass percentage. As one embodiment, the mass percentage of Fe can be ≤0.10%. This invention can strictly control harmful impurities by limiting the Fe content.

[0025] The corrosion-resistant aluminum alloy provided by this invention comprises Cu ≤ 0.05% by mass percentage. As one embodiment, the mass percentage of Cu can be 0.03~0.04%. This invention avoids deterioration of corrosion resistance by strictly controlling the copper content.

[0026] The corrosion-resistant aluminum alloy provided by this invention comprises the balance Al by weight percentage.

[0027] The corrosion-resistant aluminum alloy provided by the present invention preferably includes impurities ≤0.15% by mass percentage, with each individual impurity ≤0.05%. The present invention does not impose any particular limitation on the types of impurities; impurities well-known to those skilled in the art can be used.

[0028] This invention improves the corrosion resistance of aluminum alloys by limiting the magnesium-silicon mass ratio and using a slight excess of magnesium; through composite microalloying, it achieves a synergistic effect of iron phase modification and dispersed phase pinning at low manganese content, reducing quenching sensitivity; by adding titanium, it can achieve grain refinement; and by strictly controlling the copper content, it avoids deterioration of corrosion resistance.

[0029] The present invention also provides a method for preparing the corrosion-resistant aluminum alloy described in the above technical solution, comprising: The raw materials are mixed and then smelted and cast sequentially to obtain ingots; The ingot is subjected to homogenization annealing, hot extrusion, quenching and aging treatment in sequence to obtain a corrosion-resistant aluminum alloy.

[0030] This invention does not impose any special restrictions on the source of the raw materials; commercially available products familiar to those skilled in the art can be used.

[0031] This invention involves mixing raw materials and then sequentially smelting and casting them to obtain ingots.

[0032] In this invention, the preferred melting temperature is 720~760℃. The melting time is not particularly limited; any melting method well-known to those skilled in the art can be used. As one embodiment, the melting temperature can be 730℃, 740℃, or 750℃.

[0033] In this invention, the smelting preferably includes refining; the refining time is preferably 15-25 minutes; the refining is preferably carried out in a protective atmosphere. As one embodiment, the refining time can be 20 minutes or 22 minutes; the protective atmosphere can be nitrogen.

[0034] In one embodiment, the refining process can employ a refining agent. This invention does not impose any particular limitation on the type or amount of the refining agent; any refining agent well-known to those skilled in the art can be used. In one embodiment, the refining agent can be a chlorine-free refining agent. Both low-fluorine chlorine-free and fluorine-free chlorine-free refining agents are acceptable, suitable for industrial mass production, and conventional commercially available products are sufficient. The amount of refining agent sprayed can be 1.0~1.5 kg / ton of molten aluminum.

[0035] After smelting, the present invention preferably allows the smelted product to stand and remove slag. The present invention does not have specific limitations on the operation of this slag removal process; any operation well-known to those skilled in the art can be used.

[0036] In this invention, the casting is preferably semi-continuous casting; the casting temperature is preferably 700~730℃. As one embodiment, the casting temperature can be 710℃, 715℃, or 720℃.

[0037] This invention does not impose any special limitations on other operations in the semi-continuous casting process; operations well-known to those skilled in the art can be used. As one embodiment, the casting can be carried out under the protection of a covering agent; any general-purpose covering agent can be used, such as 550CF general-purpose aluminum covering agent, 580CF sodium-free aluminum-magnesium alloy covering agent, or RJ-2 type aluminum-magnesium alloy covering agent, etc.; the dosage of the covering agent can range from 0.8 to 1.2 kg / ton of molten aluminum. The use of a covering agent throughout the casting process in this invention can reduce magnesium burn-off.

[0038] After obtaining the ingot, the present invention sequentially performs homogenization annealing, hot extrusion, quenching and aging treatment on the ingot to obtain a corrosion-resistant aluminum alloy.

[0039] In this invention, the holding temperature for homogenization annealing is preferably 560~580℃; the holding time for homogenization annealing is preferably 8~12h; and the rate of heating to the homogenization annealing holding temperature is preferably 100~150℃ / h. This invention utilizes homogenization annealing to effectively eliminate dendrite segregation and promote the transformation of acicular β-AlFeSi phase to low-harm granular α phase. By synergistically optimizing the temperature field of high-temperature long-time homogenization annealing and hot extrusion, the hot working window is broadened, improving production efficiency while ensuring corrosion resistance.

[0040] In one embodiment, the holding temperature for homogenization annealing can be 570℃ or 575℃; the holding time for homogenization annealing can be 9h, 10h or 11h; and the rate of heating to the homogenization annealing holding temperature can be 120℃ / h.

[0041] In this invention, the preferred cooling method for the homogenization treatment is to cool the furnace to below 450°C before air cooling after removal from the furnace. This cooling method reduces the resistance to subsequent extrusion deformation.

[0042] In this invention, the preferred hot extrusion temperature is 520~540℃; the preferred extrusion ratio is (25~40):1; the die is preferably preheated before hot extrusion; the preferred preheating temperature is 480~510℃. This invention does not have a specific limitation on the preheating time; preheating to the above-mentioned temperature is sufficient. Compared with traditional high-magnesium corrosion-resistant 6-series extrusion, the hot extrusion method of this invention improves efficiency by approximately 30%.

[0043] In one embodiment, the hot extrusion temperature can be 530°C or 535°C; the hot extrusion ratio can be 26:1, 27:1, 28:1, 29:1, 30:1, 31:1, 32:1, 33:1, 34:1, 35:1, 36:1, 37:1, 38:1 or 39:1; and the preheating temperature can be 490°C, 500°C or 505°C.

[0044] In this invention, the exit speed of the profile during hot extrusion is preferably 8-12 m / min; the exit temperature during hot extrusion is preferably 510-530°C. As one embodiment, the exit speed of the profile during hot extrusion can be 9 m / min, 10 m / min, or 11 m / min; the exit temperature during hot extrusion can be 520°C or 525°C.

[0045] In this invention, the quenching is preferably online water mist quenching; the cooling rate of the quenching is preferably ≥120℃ / s; and the surface temperature of the profile after quenching is preferably reduced to below 80℃. The low quenching sensitivity design adopted in this invention can control the core-surface strength difference of large cross-section profiles to within 8%.

[0046] In one embodiment, the quenching cooling rate can be 130°C / s or 150°C / s.

[0047] In this invention, the aging treatment preferably includes sequential pre-aging, secondary grain boundary regulation aging, and tertiary stabilization aging. The holding temperature for the first pre-aging is preferably 100-120℃; the holding time for the first pre-aging is preferably 2-4 hours; the holding temperature for the secondary grain boundary regulation aging is preferably 160-170℃; the holding time for the secondary grain boundary regulation aging is preferably 1-2 hours; the holding temperature for the tertiary stabilization aging is preferably 140-150℃; and the holding time for the tertiary stabilization aging is preferably 6-8 hours. In this invention, the cooling method for the aging treatment is preferably air cooling. In this invention, the first pre-aging can induce the formation of uniformly dispersed GP region precipitates; the secondary grain boundary regulation aging can promote the preferential spheroidization and discontinuous distribution of grain boundary precipitates, interrupting continuous corrosion channels; and the tertiary stabilization aging results in the precipitation of a large number of nano-β'' strengthening phases within the grains, ultimately controlling the strength loss to within 5%, while achieving a T7 level of corrosion resistance.

[0048] The present invention does not impose any special limitation on the rate of heating to the secondary grain boundary controlled aging holding temperature; any heating rate known to those skilled in the art can be used.

[0049] The present invention does not impose any special limitation on the rate of cooling to the third-level stabilization aging holding temperature; any cooling rate known to those skilled in the art can be used.

[0050] In one implementation, the holding temperature for the first pre-aging stage can be 110°C; the holding time for the first pre-aging stage can be 3 hours; the holding temperature for the second grain boundary regulation aging stage can be 160°C or 165°C; the holding time for the second grain boundary regulation aging stage can be 1.5 hours; the holding temperature for the third stabilization aging stage can be 145°C or 150°C; and the holding time for the third stabilization aging stage can be 7 hours.

[0051] This invention employs a three-stage gradient aging process—pre-aging, grain boundary regulation, and stabilization—to control strength loss to within 5% while significantly reducing the risk of intergranular corrosion. The core of this three-stage gradient aging process is the step-by-step regulation of intragranular and grain boundary precipitation, breaking the inherent contradiction of the traditional single-stage aging process where strength and corrosion resistance are mutually exclusive. The three stages correspond to three independent yet interconnected regulatory objectives: nucleation, grain boundary shaping, and intragranular strengthening. The specific mechanism is as follows: 1. First-level low-temperature pre-aging: 100~120℃ for 2~4 hours; This step lays the foundation for subsequent high-intensity precipitation, and its core function is to achieve high-density nucleation.

[0052] At this temperature, the atomic diffusion rate is low, and a large number of GP regions (magnesium-silicon atom-rich regions) with a size of only 2-5 nm will uniformly form in the supersaturated solid solution. These GP regions are completely coherent with the aluminum matrix and can serve as uniform nucleation sites for the subsequent β'' strengthening phase. The increase in alloy strength at this stage is small, but by constructing high-density nucleation sites in advance, the problems of insufficient nucleation and coarsening of precipitated phases during subsequent high-temperature aging are avoided, ensuring the dispersion and strengthening efficiency of the final strengthening phase from the root. If this step is omitted and high-temperature aging is carried out directly, the number and size of precipitated phase nuclei will be small, and the final strength will be significantly reduced.

[0053] 2. Secondary high-temperature grain boundary conditioning aging: 160~170℃ for 1~2 hours; This step is the core process for improving corrosion resistance, and its core function is to break the spheroidization of grain boundary precipitates.

[0054] At grain boundaries, the atomic diffusion activation energy is much lower than that within the grains. At this temperature, solute atoms at grain boundaries preferentially and rapidly precipitate and coarsen and spheroidize. The grain boundary precipitate chains that were originally continuously distributed in the T6 state will transform into isolated, discontinuous granular precipitates in a short time, directly interrupting the continuous diffusion channels of intergranular corrosion and structurally eliminating the core inducing factor of intergranular corrosion. At the same time, at this temperature, only the initial transformation from the GP region to the β'' phase occurs within the grains, and the strengthening phase has not yet coarsened significantly, thus preserving the strengthening potential within the grains. The short holding time of 1-2 hours is strictly controlled to avoid excessive coarsening of the precipitates within the grains, which would lead to a decrease in strength.

[0055] 3. Level III low-temperature stabilization aging: 140~150℃ for 6~8 hours; This step is the core process for achieving the required strength, and its core function is to ensure the precipitation of intracrystalline strengthening phases and stabilize the microstructure.

[0056] This temperature range represents the optimal precipitation temperature range for the β'' strengthening phase in 6-series alloys. Relying on the high-density nucleation core formed by the first-stage pre-aging, a large amount of nanoscale, fully coherent β'' strengthening phase will precipitate within the grains, fully releasing the precipitation strengthening effect. Ultimately, the alloy strength can approach the peak aging level of traditional T6. Simultaneously, this temperature is lower than the second-stage control temperature, preventing the already formed discontinuous grain boundary precipitates from reverting to continuous chains; only slight homogenization occurs, and the corrosion-resistant structure is completely locked in. Long-term low-temperature holding further reduces the solute supersaturation of the matrix, decreases the potential difference in the solute-depleted zone at grain boundaries, and further reduces corrosion susceptibility.

[0057] In this invention, after three-stage aging, the nanoscale β'' phase forms the core, with a monoclinic lattice (space group C2 / m), completely coherent with the matrix, and is the main source of strength; it also contains a small amount of metastable β' phase (hexagonal lattice); it further includes a dispersed strengthening phase: Al3(Zr,Er) intermetallic compound, with an L12-type ordered face-centered cubic lattice, coherent with the matrix, which acts as a grain boundary pinning and inhibits recrystallization; and an impurity phase: iron mainly in the form of α-Al 15 The (Fe,Mn)3Si2 phase exists, which is a body-centered cubic lattice, and is uniformly distributed in granular form. It has a small potential difference with the matrix and has low harm to corrosion resistance.

[0058] The experimental data for the 6-series aluminum alloy provided by this invention are as follows: 1. Mechanical properties The tensile strength Rm is 290~320MPa; The elongation after fracture is 12-16%; Brinell hardness HBW is 90~105HB; The specified plastic elongation strength is 240~270 MPa; The above data was tested according to GB / T 16865-2023.

[0059] Compared to the traditional single-stage T7 process (which generally results in a 10% to 15% loss in strength), the strength loss of this invention is controlled within 5%. At the same time, due to the spheroidization of the iron phase and the improvement of the uniformity of the microstructure, the plasticity is actually better than that of conventional T6 alloys, and the strength and toughness are more balanced.

[0060] 2. Corrosion resistance 1) Intergranular corrosion performance GB / T 7998-2005 The aluminum alloy of the present invention has a maximum intergranular corrosion depth of ≤0.05mm after standard immersion test, and a corrosion level of 1~2 (pitting / mild intergranular corrosion), with no penetrating intergranular corrosion; Compared to conventional 6061-T6, which is typically grade 3-4 (medium / severe intergranular corrosion) with a maximum corrosion depth of over 0.2 mm, this invention improves intergranular corrosion resistance by more than 4 times, reaching the intergranular corrosion resistance level of T7 over-aged alloys.

[0061] 2) Neutral salt spray corrosion performance GB / T 10125-2012 (Neutral Salt Spray NSS) The aluminum alloy of this invention exhibits a surface pitting corrosion rating ≥9 (GB / T 6461) and a corrosion weight loss per unit area ≤0.5 mg / cm³ after a 1000-hour neutral salt spray test. 2 ; Benchmark: Under the same conditions, conventional 6061-T6 has a pitting corrosion rating of approximately 7-8, and a corrosion weight loss of approximately 1.0-1.2 mg / cm³.2 The invention improves pitting resistance by approximately 100%.

[0062] 3) Stress corrosion cracking performance (SCC) Slow strain rate tensile test (SSRT) was conducted in a 3.5% NaCl aqueous solution.

[0063] Under the condition of a loading stress of 75% of the yield strength, this invention exhibits no tendency for stress corrosion cracking; slow tensile specimens (constant strain rate: 1×10⁻⁶) -6 The stress corrosion sensitivity coefficient of / S) is ≤0.15, and the fracture time is more than 3 times that of conventional 6061-T6; Compared to conventional 6061-T6, under the same conditions, the sensitivity coefficient is about 0.35~0.45, and it is prone to intergranular stress corrosion cracking.

[0064] 3. Hot extrusion performance: The extrusion exit speed can reach 8~12m / min, which is about 30% higher than that of high magnesium corrosion-resistant 6-series alloys of the same strength grade, and the yield of complex cross-section profiles is ≥92%.

[0065] 4. Surface treatment performance: It exhibits excellent compatibility with anodizing, with a uniform gloss on a 10μm thick anodized film, a color difference ΔE≤1.5, no obvious iron phase streaks, and superior decorative properties compared to conventional high-impurity 6-series alloys.

[0066] 5. Welding performance: After welding with argon arc welding, the weld strength coefficient is ≥0.75, and there is no significant decrease in corrosion sensitivity in the heat-affected zone, making it suitable for use in welded structural components.

[0067] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0068] Example 1 The aluminum alloy has the following composition by mass percentage: Si 0.50%, Mg 1.00%, Mn 0.20%, Zr 0.10%, Er 0.05%, Ti 0.02%, Fe 0.10%, Cu 0.03%, and the balance Al; The mass ratio of Mg to Si is 2.0; The raw materials are mixed and smelted, then allowed to stand to remove slag before semi-continuous casting at 715℃. The entire molten surface is protected with a covering agent (550CF general-purpose aluminum covering agent, AdTech) to obtain ingots. The smelting temperature is 740℃, and 5N grade high-purity nitrogen and chlorine-free refining agent (SATA-GF-M12 granular refining agent) are sprayed for 20 minutes for refining at a rate of 1.2 kg / ton of molten aluminum. The covering agent is used at a rate of 1 kg / ton of molten aluminum. The ingot was heated to 570℃ at a rate of 120℃ / h and held for 10h for homogenization annealing. Then, it was cooled in the furnace to 420℃ and then air-cooled. Subsequently, the mold was preheated to 500℃, and then the ingot was heated to 530℃. The extrusion ratio was 30:1, the exit speed of the profile was 10m / min, and the outlet temperature was 520℃. After the profile was extruded from the mold, it was immediately subjected to water mist quenching at a cooling rate of 150℃ / s. After quenching, the surface temperature of the profile dropped to below 60℃. Then, it was held at 110℃ for 3h for first-stage pre-aging. Second-stage grain boundary control aging was performed by heating to 165℃ at a rate of 45℃ / h and holding for 1.5h. Third-stage stabilization aging was performed by cooling to 145℃ and holding for 7h. After aging, it was air-cooled to obtain the aluminum alloy.

[0069] The properties of the aluminum alloy prepared in Example 1 were tested and are as follows: The tensile strength is 295 MPa, the specified ductile elongation is 245 MPa, the elongation after fracture is 15%, the Brinell hardness (HBW5 / 750) is 95 HBW, the maximum depth of intergranular corrosion (GB / T7998) is 0.03 mm, the corrosion grade is Class 1, the stress corrosion susceptibility coefficient (3.5% NaCl, SSRT) is 0.12, the 1000h neutral salt spray pitting corrosion rating (GB / T6461) is 9.5, and the corrosion weight loss per unit area is 0.35 mg / cm³. 2 .

[0070] Example 2 The aluminum alloy has the following composition by mass percentage: Si 0.60%, Mg 1.10%, Mn 0.25%, Zr 0.12%, Er 0.06%, Ti 0.02%, Fe 0.12%, Cu 0.04%, and the balance Al; The mass ratio of Mg to Si is 1.83; The raw materials are mixed and smelted, then allowed to stand to remove slag before being semi-continuously cast at 720°C. The entire molten surface is protected with a covering agent (550CF general-purpose aluminum covering agent, AdTech) to obtain ingots. The smelting temperature is 750°C, and 5N grade high-purity nitrogen and chlorine-free refining agent (SATA-GF-M12 granular refining agent) are sprayed for 22 minutes for refining at a rate of 1.2 kg / ton of molten aluminum. The covering agent is used at a rate of 1 kg / ton of molten aluminum. The ingot was heated to 575℃ at a rate of 130℃ / h and held for 10 hours for homogenization annealing. Then, it was cooled in the furnace to 430℃ and then air-cooled. Subsequently, the mold was preheated to 505℃, and the ingot was heated to 535℃. The extrusion ratio was 35:1, the exit speed of the profile was 9m / min, and the outlet temperature was 525℃. After the profile was extruded from the mold, it was immediately subjected to water mist quenching at a cooling rate of 130℃ / s. After quenching, the surface temperature of the profile dropped to below 70℃. Then, it was held at 110℃ for 3 hours for primary pre-aging. Secondary grain boundary control aging was performed by heating to 160℃ at a rate of 40℃ / h and holding for 1.5 hours. Tertiary stabilization aging was performed by cooling to 150℃ and holding for 7 hours. After aging, it was air-cooled to obtain the aluminum alloy.

[0071] The properties of the aluminum alloy prepared in Example 2 were tested and are as follows: The tensile strength is 315 MPa, the specified ductile elongation is 265 MPa, the elongation after fracture is 13%, the Brinell hardness (HBW5 / 750) is 102 HBW, the maximum depth of intergranular corrosion (GB / T7998) is 0.045 mm, the corrosion grade is 2, the stress corrosion susceptibility coefficient (3.5% NaCl, SSRT) is 0.14, the 1000h neutral salt spray pitting corrosion rating (GB / T6461) is 9, and the corrosion weight loss per unit area is 0.45 mg / cm³. 2 .

[0072] Comparative Example 1 The first-level pre-aging is omitted from Example 1, while other conditions remain unchanged.

[0073] Comparative Example 1 lacks high-density GP region nucleation cores, resulting in a reduction in the number and size of the β'' phase within the crystal, and a significant decrease in strength; the grain boundary structure is unaffected, but the corrosion resistance decreases slightly.

[0074] Comparative Example 2 Based on Example 1, the holding time for secondary grain boundary regulation aging was modified to 4 hours, while other conditions remained unchanged.

[0075] In Comparative Example 2, the holding time for secondary grain boundary regulation aging was too long, resulting in discontinuous spheroidization of the grain boundary precipitates and a slight improvement in corrosion resistance. However, the prolonged high temperature caused extensive coarsening of the pre-formed GP region within the grains, coarsening of the strengthening phase, and a significant reduction in strength.

[0076] Comparative Example 3 Based on Example 1, the heat preservation time for the third-level stabilization aging was modified to 2 hours, while other conditions remained unchanged.

[0077] In Comparative Example 3, the holding time during the third-stage stabilization aging was insufficient, resulting in incomplete transformation of the GP region within the crystal to the β'' phase and failure to reach the peak strength. Furthermore, the matrix solute saturation was too high, leading to an increase in the potential difference of the solute-depleted zone at the grain boundaries and a deterioration in corrosion resistance.

[0078] Comparative Example 4 Based on Example 1, the heat preservation temperature for the third-stage stabilization aging was modified to 155°C, while other conditions remained unchanged.

[0079] The holding temperature of the third-stage stabilization aging in Comparative Example 4 was too high, causing the nano β'' phase to partially transform into the coarse β' phase, resulting in a decrease in the strengthening effect; at the same time, the high temperature caused slight reconnection of the grain boundary precipitates, increasing the intergranular corrosion sensitivity.

[0080] The properties of the aluminum alloys prepared in Comparative Examples 1 to 4 are shown in Table 1.

[0081] Table 1 Properties of aluminum alloys prepared in Comparative Examples 1-4

[0082] As can be seen from the above embodiments and comparative examples, the aluminum alloy provided by the present invention has excellent corrosion resistance.

[0083] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A corrosion-resistant aluminum alloy comprising the following components by mass percentage: Si 0.45~0.65%, Mg 0.85~1.15%, Mn 0.15~0.30%, Zr 0.08~0.15%, Er 0.03~0.08%, Ti 0.01~0.03%, Fe≤0.12%, Cu≤0.05%, and the balance Al; The mass ratio of Mg to Si is 1.8 to 2.

0.

2. The corrosion-resistant aluminum alloy according to claim 1, characterized in that, It includes the following components by mass percentage: Si 0.50~0.60%, Mg 1.00~1.10%, Mn 0.20~0.25%, Zr 0.10~0.12%, Er 0.05~0.06%, Ti 0.02~0.03%, Fe≤0.10%, Cu≤0.04%, and the balance Al.

3. The corrosion-resistant aluminum alloy according to claim 1 or 2, characterized in that, The mass ratio of Mg to Si is 1.83 to 1.

95.

4. A method for preparing the corrosion-resistant aluminum alloy according to any one of claims 1 to 3, comprising: The raw materials are mixed and then smelted and cast sequentially to obtain ingots; The ingot is subjected to homogenization annealing, hot extrusion, quenching and aging treatment in sequence to obtain a corrosion-resistant aluminum alloy.

5. The preparation method according to claim 4, characterized in that, The casting is a semi-continuous casting process, and the casting temperature is 700~730℃.

6. The preparation method according to claim 4, characterized in that, The holding temperature for homogenization annealing is 560~580℃, the holding time for homogenization annealing is 8~12h, and the rate of heating to the homogenization annealing holding temperature is 100~150℃ / h.

7. The preparation method according to claim 4, characterized in that, The hot extrusion temperature is 520~540℃, and the hot extrusion ratio is (25~40):

1.

8. The preparation method according to claim 4, characterized in that, The quenching is an online water mist quenching, and the cooling rate of the quenching is ≥120℃ / s.

9. The preparation method according to claim 4, characterized in that, The aging process includes sequential pre-aging, secondary grain boundary regulation aging, and tertiary stability aging. The holding temperature for the first pre-aging is 100~120℃, and the holding time for the first pre-aging is 2~4h; The holding temperature for the secondary grain boundary regulation aging is 160~170℃, and the holding time for the secondary grain boundary regulation aging is 1~2h. The holding temperature for the third-stage stabilization aging is 140~150℃, and the holding time for the third-stage stabilization aging is 6~8h.

10. The preparation method according to claim 9, characterized in that, The first pre-aging temperature is 110℃, and the first pre-aging time is 3 hours. The holding temperature for the secondary grain boundary regulation aging is 160~165℃, and the holding time for the secondary grain boundary regulation aging is 1.5h. The holding temperature for the third-stage stabilization aging is 145~150℃, and the holding time for the third-stage stabilization aging is 7h.

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