Strengthening method and preparation process of high-strength corrosion-resistant aluminum alloy

Abstract

The invention discloses a strengthening method and a preparation process of a high-strength corrosion-resistant aluminum alloy, and relates to the technical field of aluminum alloy materials.The strengthening method comprises the following steps that 1-3% pre-stretching treatment is conducted on a 7-series aluminum alloy profile obtained after solid solution quenching, and a dislocation network with the dislocation density larger than or equal to 10 < 14 > m <-2 > is introduced; by controlling specific chemical components of the 7-series aluminum alloy, a foundation is laid for high performance of the material, by means of a pre-stretching-aging synergistic process, residual stress is released through plastic deformation in pre-stretching, follow-up machining deformation and stress corrosion cracking risks are reduced, a dislocation network formed by pre-stretching provides a large number of uniform nucleation points for a strengthening phase, and the stress corrosion cracking risk is reduced. By combining two-stage aging and stretching regulation, uniform dispersed precipitation of a nanoscale eta'phase is promoted, generation of a thick eta phase is inhibited, meanwhile, the nucleation tendency of a strengthening phase at a grain boundary is reduced, a fine discontinuous grain boundary precipitated phase and a narrow lean solute region are formed, intergranular corrosion resistance and exfoliation corrosion resistance are remarkably improved, and balance of strength, toughness and corrosion resistance is achieved.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy materials technology, specifically to a strengthening method and preparation process for high-strength corrosion-resistant aluminum alloys. Background Technology

[0002] Aluminum alloys are alloy materials composed of aluminum as the base material and one or more other elements (such as copper, magnesium, zinc, etc.). They combine the lightweight characteristics of aluminum with the advantages of high strength and good machinability brought by alloying. They play an irreplaceable role in many fields such as aerospace, transportation, and machinery manufacturing. They are key materials for promoting the development of industrial lightweighting and energy conservation. With the rapid development of high-end equipment manufacturing, higher requirements have been placed on the performance of aluminum alloys. High-strength corrosion-resistant aluminum alloys have emerged. These aluminum alloys not only need to have ultra-high strength to meet the structural load-bearing requirements, but also need to have excellent corrosion resistance to adapt to complex and harsh service environments.

[0003] However, in the pursuit of high strength, traditional 7-series aluminum alloys often face the problem of difficulty in controlling the strengthening phase. Either the strength is insufficient due to the coarse strengthening phase (such as the η phase), or the corrosion resistance is reduced due to the uneven distribution of grain boundary precipitates and the excessively wide solute-depleted region. It is difficult to achieve a balance between high strength and high corrosion resistance at the same time. At the same time, the synergistic effect of pre-stretching and aging in the existing process has not been fully optimized, resulting in the inability to effectively release the residual stress in the material. The risk of subsequent processing deformation and stress corrosion cracking is high. Moreover, the quantitative control of process parameters during production is insufficient, which affects the stability of product performance. Therefore, it is of great significance to develop a strengthening method and preparation process for high-strength and corrosion-resistant aluminum alloys. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a strengthening method and preparation process for high-strength and corrosion-resistant aluminum alloys. It can lay the foundation for performance by precisely controlling the chemical composition of 7-series aluminum alloys, release residual stress through a pre-stretching-aging synergistic process, reduce processing deformation and stress corrosion risk, promote uniform dispersion precipitation of nanoscale η' phase through dislocation network, inhibit the formation of coarse phases, reduce the nucleation of grain boundary strengthening phases, form an optimized grain boundary structure, improve corrosion resistance, achieve a balance between strength, toughness and corrosion resistance, and optimize the process to improve production feasibility and stability.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for strengthening high-strength corrosion-resistant aluminum alloys, the method comprising the following steps:

[0006] 7-series aluminum alloy profiles that have undergone solution quenching are subjected to a 1-3% pre-stretching treatment to introduce a dislocation density ≥10. 14 m -2The dislocation network of the 7-series aluminum alloy, wherein the composition satisfies Si < 0.07%, Fe ≤ 0.12%, Cu 0.3-0.35%, Mn 0.07-0.17%, Mg 2.10-2.40%, Cr 0.003-0.012%, Zn 5.9-6.3%, and Ti 0.003-0.020%;

[0007] The pre-stretched profile is subjected to low-temperature aging at 110℃ for 2.5 hours to form a high-density GP zone;

[0008] The profiles that have undergone low-temperature aging are subjected to a secondary stretching of 10%.

[0009] The profile after secondary stretching was subjected to high-temperature aging at 155℃ for 10 hours to promote the transformation of the GP region into the 5-15nm nanoscale η' phase.

[0010] The profiles after high-temperature aging are subjected to a final stretch of 4-6%.

[0011] Furthermore, the pre-stretching treatment is achieved through unidirectional plastic deformation along the length of the profile, with the deformation rate controlled at 5-10 mm / min. Stress changes are monitored in real time during the deformation process, and stretching is stopped when the residual stress release rate reaches 60-70%, forming a uniformly distributed dislocation network configuration.

[0012] Furthermore, the low-temperature aging is carried out in an air-circulating oven with a heating rate of 5-8℃ / min. After reaching 110℃, the temperature is kept constant. Inert gas is used for protection during the aging process to avoid surface oxidation. The size of the GP region is controlled at 2-5nm.

[0013] Furthermore, the high-temperature aging is carried out in a vacuum aging furnace with a vacuum degree ≥0.1Pa and a heating rate of 3-5℃ / min. During the 155℃ constant temperature stage, the internal temperature uniformity of the profile is monitored in real time by infrared thermography, and the temperature difference is controlled within ±2℃. The η' phase is uniformly precipitated on the dislocation lines inside the grain.

[0014] A preparation process for a high-strength, corrosion-resistant aluminum alloy, comprising the following steps:

[0015] The intermediate elements were prepared and smelted according to the composition of Si < 0.07%, Fe ≤ 0.12%, Cu 0.3-0.35%, Mn 0.07-0.17%, Mg 2.10-2.40%, Cr 0.003-0.012%, Zn 5.9-6.3%, and Ti 0.003-0.020%, and the resulting ingots were cast after slag and gas removal.

[0016] Homogenize the ingots;

[0017] The homogenized ingot is extruded into profiles;

[0018] The profiles are subjected to solution quenching treatment;

[0019] The quenched profiles are subjected to strengthening treatments in sequence, including 1-3% pre-stretching, low-temperature aging at 110℃ for 2.5h, 10% secondary stretching, high-temperature aging at 155℃ for 10h, and 4-6% final stretching.

[0020] The reinforced profiles are then machined and surface-treated to obtain the finished product.

[0021] Furthermore, the melting is carried out in a graphite crucible at a melting temperature of 720-750℃. The alloying elements are added in the order of Zn, Mg, Cu, Mn, Cr, Ti, and Si. The stirring rate is 300-500 r / min and the stirring time is 15-20 min. Argon gas is used for degassing at a rate of 0.5-1 L / min for 20-30 min.

[0022] Furthermore, the homogenization process is carried out in a box-type resistance furnace with a heating rate of 100-150℃ / h, a holding temperature of 460-480℃ for 8-12 hours, and then cooling to below 150℃ at a rate of 50-80℃ / h. After being removed from the furnace, the furnace is allowed to cool naturally to room temperature, followed by natural aging for 24-48 hours.

[0023] Furthermore, the extrusion molding adopts a horizontal extruder, the ingot heating temperature is 420-450℃, the die preheating temperature is 400-430℃, the extrusion rate is controlled by a servo system to be 10-15m / min, water spray is used to cool the profile surface during the extrusion process, and after cooling to 200-250℃, it is air-cooled to room temperature, and the extrusion ratio is 20-30:1.

[0024] Furthermore, the solution treatment is carried out in a continuous solution furnace, held at 470-490℃ for 1-2 hours, and immediately after the holding period, water quenching is performed. The quenching medium is deionized water at 20-30℃, and the water flow rate is 10-15m / s, so that the cooling rate of the core of the profile is ≥200℃ / s, and the water film on the surface of the profile falls off within 30s after quenching.

[0025] Compared with existing technologies, the strengthening method and preparation process of this high-strength corrosion-resistant aluminum alloy have the following advantages:

[0026] Beneficial effects:

[0027] This invention lays the foundation for high-performance materials by precisely controlling the specific chemical composition of 7-series aluminum alloys. Utilizing a pre-stretching-aging synergistic process, pre-stretching releases residual stress through plastic deformation, reducing the risk of subsequent processing deformation and stress corrosion cracking. The dislocation network formed by pre-stretching provides numerous uniform nucleation sites for the strengthening phase. Combined with two-stage aging and stretching control, it promotes the uniform and dispersed precipitation of nanoscale η' phases, inhibits the formation of coarse η phases, and reduces the nucleation tendency of the strengthening phase at grain boundaries, forming fine, discontinuous grain boundary precipitates and narrow solute-poor regions. This significantly improves resistance to intergranular corrosion and exfoliation corrosion, achieving a balance between strength, toughness, and corrosion resistance. Quantitative process optimization enhances production feasibility and stability.

[0028] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0030] Figure 1 A flowchart of a strengthening method for a high-strength, corrosion-resistant aluminum alloy;

[0031] Figure 2 This is a flowchart illustrating a strengthening method for a high-strength, corrosion-resistant aluminum alloy.

[0032] Figure 3 This is a flowchart of a method for preparing a high-strength, corrosion-resistant aluminum alloy. Detailed Implementation

[0033] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0034] The high-strength, corrosion-resistant aluminum alloy strengthening method of this invention is applied to 7-series aluminum alloy profiles after solution quenching. The composition of this 7-series aluminum alloy satisfies the following conditions: Si < 0.07%, Fe ≤ 0.12%, Cu 0.3-0.35%, Mn 0.07-0.17%, Mg 2.10-2.40%, Cr 0.003-0.012%, Zn 5.9-6.3%, and Ti 0.003-0.020%. (See [reference needed]). Figure 1 and Figure 2 The specific steps are as follows:

[0035] After solution quenching, the profile is subjected to a 1-3% pre-stretching treatment, followed by unidirectional plastic deformation along the length of the profile. The deformation rate is controlled at 5-10 mm / min, and stress changes are monitored in real time. The deformation is stopped when the residual stress release rate reaches 60-70%, thereby introducing a dislocation density ≥10. 14 m -2 A uniform dislocation network.

[0036] The pre-stretched profile is placed in an air-circulating oven and heated to 110°C at a rate of 5-8°C / min. It is then aged at low temperature for 2.5 hours under inert gas protection to form a high-density GP region with a size of 2-5nm.

[0037] The profiles that have undergone low-temperature aging are subjected to a 10% secondary stretch.

[0038] The profile after secondary stretching is placed in a vacuum aging furnace with a vacuum degree ≥0.1Pa and heated to 155℃ at a rate of 3-5℃ / min. The temperature uniformity is monitored by infrared thermometry (temperature difference within ±2℃). The high-temperature aging is carried out for 10 hours to promote the transformation of the GP region into a 5-15nm nanoscale η' phase that is uniformly precipitated on the dislocation lines inside the grain.

[0039] The profiles after high-temperature aging are subjected to a final stretch of 4-6%.

[0040] This strengthening method introduces a high-density dislocation network through pre-stretching, and combines two-stage aging with multiple stretching controls to achieve uniform dispersion precipitation of the nanoscale η' phase, effectively releasing residual stress, while optimizing the grain boundary structure to achieve a balance between strength, toughness and corrosion resistance.

[0041] See Figure 3 The preparation process of this high-strength corrosion-resistant aluminum alloy is carried out according to the following steps:

[0042] The intermediate elements are prepared according to the above 7-series aluminum alloy composition. The alloy is then melted in a graphite crucible at 720-750℃. Alloying elements are added in the order of Zn, Mg, Cu, Mn, Cr, Ti, and Si. The mixture is stirred at 300-500 r / min for 15-20 min, and then degassed by argon gas at 0.5-1 L / min for 20-30 min. After slag removal, the ingot is cast.

[0043] The ingots are homogenized in a box-type resistance furnace, heated to 460-480℃ at 100-150℃ / h and held for 8-12 hours, then cooled to below 150℃ with the furnace at 50-80℃ / h. After being taken out of the furnace and naturally cooled to room temperature, they are naturally aged for 24-48 hours.

[0044] The homogenized ingot is extruded into shape using a horizontal extrusion press. The ingot is heated to 420-450℃, and the die is preheated to 400-430℃. The extrusion rate is controlled by a servo system at 10-15m / min. During the extrusion process, the surface of the profile is cooled by water spray to 200-250℃ and then air-cooled to room temperature. The extrusion ratio is 20-30:1.

[0045] The profile is subjected to solution quenching treatment. It is held at 470-490℃ for 1-2 hours in a continuous solution furnace. After the holding time is completed, it is immediately quenched with deionized water at 20-30℃ with a water flow rate of 10-15m / s to ensure that the cooling rate of the core of the profile is ≥200℃ / s and that the water film on the surface of the profile falls off within 30s after quenching.

[0046] The quenched profiles are subjected to the following strengthening treatments in sequence: 1-3% pre-stretching, 110℃×2.5h low-temperature aging, 10% secondary stretching, 155℃×10h high-temperature aging, and 4-6% final stretching.

[0047] The reinforced profiles are then machined and surface-treated to obtain the finished product.

[0048] This preparation process starts with precise batching and smelting, followed by pretreatment processes such as homogenization, extrusion, and solution quenching. It then combines core strengthening processes to optimize the microstructure and ensures high product performance and stability through quantitative control of parameters throughout the entire process.

[0049] Example 1

[0050] This embodiment provides a complete preparation and strengthening scheme for high-strength and corrosion-resistant 7-series aluminum alloys. The specific steps are as follows:

[0051] Raw material preparation and smelting: each element is accurately weighed according to chemical composition requirements: Si is controlled at 0.05%, Fe content is 0.10%, Cu is added at 0.32%, Mn is added at 0.12%, Mg ratio is 2.25%, Cr is set at 0.008%, Zn is adjusted at 6.1%, and Ti is added at 0.012%. The raw materials are added to a graphite crucible and smelted at 735℃. Alloying elements are added in the order of Zn, Mg, Cu, Mn, Cr, Ti, and Si. The stirring rate is set at 400 r / min and stirring is carried out continuously for 18 min to ensure uniform composition. Argon gas is used for degassing at a rate of 0.8 L / min for 25 min to effectively remove gaseous impurities from the melt. After slag removal, the melt is cast into an ingot with a diameter of 120 mm.

[0052] The ingot is homogenized by placing it in a box-type resistance furnace. The heating rate is controlled at 120℃ / h. After heating to 470℃, it is held for 10h to homogenize the internal composition and structure of the ingot. Then, it is cooled to 140℃ in the furnace at a rate of 65℃ / h. After being taken out of the furnace, it is naturally cooled to room temperature and then subjected to natural aging for 36h to further stabilize the performance of the ingot.

[0053] Extrusion molding is performed using a horizontal extruder to extrude the homogenized ingot into profiles with a cross-section of 50mm × 10mm. The ingot heating temperature is controlled at 435℃, and the die is preheated to 415℃. The extrusion rate is stabilized at 12m / min through a servo system. During the extrusion process, water spray is used to cool the surface of the profile, and the temperature is controlled at 220℃ before air cooling to room temperature. The extrusion ratio is set at 25:1 to ensure that the profile has good mechanical properties.

[0054] Solution quenching treatment involves placing the extruded profile into a continuous solution furnace and holding it at 480℃ for 1.5 hours. Immediately after holding, water quenching is performed using deionized water at 25℃ as the quenching medium and a water flow rate of 12 m / s to ensure that the cooling rate of the core of the profile reaches 220℃ / s. After quenching, the water film on the surface of the profile falls off within 25 seconds to avoid surface oxidation and performance degradation.

[0055] Pre-stretching: The solution-quenched profile is pre-stretched by 2%, and unidirectional plastic deformation is performed along the length of the profile. The deformation rate is controlled at 8 mm / min. Stress changes are monitored in real time during deformation. Stretching is stopped when the residual stress release rate reaches 65%. At this point, the dislocation density inside the profile is 1.2 × 10⁻⁶. 14 m -2 A uniform dislocation network.

[0056] Low-temperature aging: The pre-stretched profile is placed in an air-circulating oven and heated to 110°C at a rate of 6°C / min. It is then kept at this temperature for 2.5 hours under nitrogen protection to form a high-density GP region with a size of 3-4nm, while avoiding oxidation of the profile surface.

[0057] Secondary stretching: The profiles that have undergone low-temperature aging are subjected to a 10% secondary stretch to further optimize the dislocation structure.

[0058] High-temperature aging: The profile after secondary stretching is placed in a vacuum aging furnace with a vacuum degree of 0.08 Pa and heated to 155℃ at a heating rate of 4℃ / min. The internal temperature of the profile is monitored in real time by infrared thermography to ensure that the temperature difference is controlled within ±1.5℃. The temperature is maintained for 10 hours to promote the transformation of the GP region into the 8-12nm nanoscale η' phase, and the η' phase is uniformly precipitated on the dislocation lines inside the grain.

[0059] Final stretching: The profile after high-temperature aging is subjected to a 5% final stretch to further improve the material properties.

[0060] The reinforced profile is then machined to precisely control its dimensional accuracy, followed by surface treatment to improve its corrosion resistance and surface quality, ultimately yielding a high-strength, corrosion-resistant aluminum alloy product.

[0061] This embodiment lays the foundation for high-performance materials by precisely controlling the chemical composition of 7-series aluminum alloys. During the preparation process, the initial properties of the material are ensured by optimizing process parameters such as melting, homogenization, extrusion, and solution quenching. In the strengthening treatment stage, a pre-stretching-aging synergistic process is adopted. Pre-stretching effectively releases residual stress, reduces the risk of subsequent processing deformation and stress corrosion cracking, and the resulting high-density dislocation network provides a large number of uniform nucleation sites for the strengthening phase. Combined with two-stage aging and multiple stretching controls, the uniform and dispersed precipitation of nanoscale η' phase is successfully promoted, the formation of coarse η phase is suppressed, and the nucleation tendency of the strengthening phase at grain boundaries is reduced, forming fine and discontinuous grain boundary precipitates and narrow solute-poor regions. Finally, through subsequent treatment, the prepared aluminum alloy product achieves a good balance in terms of strength, toughness, and corrosion resistance, and has excellent comprehensive performance, which can meet the application requirements of high-end fields such as aerospace and transportation.

[0062] Example 2

[0063] This embodiment provides another preparation and strengthening technology for high-strength and corrosion-resistant 7-series aluminum alloys. The detailed steps are as follows:

[0064] Raw material preparation and smelting: The raw materials are prepared according to the chemical composition requirements: Si content 0.06%, Fe content 0.11%, Cu addition 0.33%, Mn addition 0.09%, Mg ratio 2.30%, Cr setting 0.005%, Zn adjustment 6.0%, and Ti addition 0.008%. The raw materials are placed in a graphite crucible and smelted at 740℃. The alloying elements are added in the order of Zn, Mg, Cu, Mn, Cr, Ti, and Si. The stirring rate is 350 r / min and the stirring time is 16 min to ensure that the alloying elements are fully dissolved and uniform. Argon gas is used for degassing at a rate of 0.6 L / min for 28 min to effectively remove the gas in the melt. After slag removal, the melt is cast into an ingot with a diameter of 100 mm.

[0065] The ingot is homogenized by placing it in a box-type resistance furnace. The heating rate is controlled at 130℃ / h. After heating to 465℃, it is held for 9 hours. Then, it is cooled to 130℃ with the furnace at a rate of 70℃ / h. After being taken out of the furnace, it is naturally cooled to room temperature and then naturally aged for 40 hours to make the internal structure and composition of the ingot more uniform and stable.

[0066] Extrusion molding is performed using a horizontal extruder to extrude the homogenized ingot into profiles with a cross-section of 40mm × 15mm. The ingot heating temperature is 440℃, the die preheating is 420℃, and the extrusion rate is controlled by a servo system at 13m / min. During the extrusion process, water spray is used to cool the profile surface. After cooling to 230℃, it is air-cooled to room temperature. The extrusion ratio is set to 28:1 to ensure the forming quality and initial performance of the profile.

[0067] Solution quenching treatment involves placing the extruded profile into a continuous solution furnace and holding it at 475℃ for 1.2 hours. Immediately after holding, water quenching is performed using deionized water at 28℃ as the quenching medium and a water flow rate of 13 m / s to ensure that the cooling rate of the core of the profile reaches 210℃ / s. After quenching, the water film on the surface of the profile falls off within 28 seconds to ensure the quenching effect.

[0068] Pre-stretching: The solution-quenched profile is pre-stretched by 1.5%, and unidirectional plastic deformation is performed along the length of the profile. The deformation rate is controlled at 6 mm / min, and stress changes are monitored in real time. Stretching is stopped when the residual stress release rate reaches 62%. At this point, the dislocation density inside the profile is 1.1 × 10⁻⁶. 14 m -2 A uniform dislocation network.

[0069] Low-temperature aging: The pre-stretched profile is placed in an air-circulating oven and heated to 110°C at a rate of 7°C / min. It is then kept at this temperature for 2.5 hours under argon protection to form a high-density GP region with a size of 2-3 nm, thus preventing surface oxidation.

[0070] Secondary stretching: The profiles that have undergone low-temperature aging are subjected to a 10% secondary stretch to optimize the dislocation configuration.

[0071] High-temperature aging: The profile after secondary stretching is placed in a vacuum aging furnace with a vacuum degree of 0.09 Pa and heated to 155℃ at a heating rate of 3.5℃ / min. The internal temperature of the profile is monitored in real time by infrared thermography, and the temperature difference is controlled within ±1.8℃. The temperature is maintained for 10 hours to promote the transformation of the GP region into the 5-10nm nanoscale η' phase, and the η' phase is uniformly distributed on the dislocation lines inside the grain.

[0072] Final stretching: The profile after high-temperature aging is subjected to a final stretch of 4.5% to further improve the mechanical properties of the material.

[0073] The reinforced profile is then machined to ensure dimensional accuracy meets requirements, followed by surface treatment to enhance its corrosion resistance and surface aesthetics, resulting in a high-strength, corrosion-resistant aluminum alloy finished product.

[0074] This embodiment also relies on precise control of the composition of 7-series aluminum alloys. Through a rationally designed smelting process, the purity and compositional uniformity of the raw materials are ensured. In the ingot homogenization process, optimized process parameters promote the diffusion of alloying elements and reduce casting defects. During the extrusion molding process, precise control of temperature and rate results in good initial microstructure and properties of the profile. Solution quenching lays a good microstructure foundation for subsequent strengthening processes. During the strengthening process, pre-stretching effectively releases residual stress and introduces high-density dislocations. The synergistic effect of double-stage aging and multiple stretching successfully achieves uniform dispersion precipitation of nanoscale η' phase, suppresses the formation of coarse phases, and optimizes the grain boundary structure. Through the synergistic effect of this series of processes, the prepared aluminum alloy product has high strength, good toughness, and excellent corrosion resistance, exhibiting excellent comprehensive performance. The process parameters in this embodiment are reasonably set, with good production feasibility and stability, and can meet the needs of different high-end equipment manufacturing fields for high-strength and corrosion-resistant aluminum alloy materials.

[0075] Example 3

[0076] This embodiment provides another preparation and strengthening technology for high-strength and corrosion-resistant 7-series aluminum alloys. The specific steps are as follows:

[0077] Raw material preparation and smelting: The raw materials are prepared according to the chemical composition requirements: Si content 0.04%, Fe content 0.09%, Cu addition 0.34%, Mn addition 0.15%, Mg ratio 2.15%, Cr setting 0.010%, Zn adjustment 6.2%, and Ti addition 0.018%. The raw materials are placed in a graphite crucible and smelted at 725℃. The alloying elements are added in the order of Zn, Mg, Cu, Mn, Cr, Ti, and Si. The stirring rate is 450 r / min and the stirring time is 19 min. Argon gas is used for degassing at a rate of 0.9 L / min for 22 min. After slag removal, the material is cast into an ingot with a diameter of 110 mm.

[0078] For ingot homogenization treatment, the ingot is placed in a box-type resistance furnace, heated at a rate of 140℃ / h, and held at 475℃ for 11 hours. Then, it is cooled to 145℃ with the furnace at a rate of 55℃ / h. After being removed from the furnace, it is naturally cooled to room temperature and then naturally aged for 28 hours.

[0079] Extrusion molding is performed by using a horizontal extruder to extrude the ingot into a profile with a cross-section of 45mm×12mm. The ingot is heated to 430℃, the die is preheated to 410℃, and the extrusion rate is controlled by a servo system at 11m / min. During the extrusion process, the profile surface is cooled to 210℃ by water spray and then air-cooled to room temperature. The extrusion ratio is set to 22:1.

[0080] Solution hardening treatment involves placing the profile into a continuous solution furnace and holding it at 485℃ for 1.8 hours. Immediately after the holding period, the profile is quenched with 22℃ deionized water at a flow rate of 14m / s to ensure a cooling rate of 230℃ / s for the core of the profile. The water film on the surface of the profile falls off within 22 seconds after quenching.

[0081] Pre-stretching: The solution-quenched profile is pre-stretched by 2.5%, and unidirectional plastic deformation is performed along the length at a rate of 7 mm / min. The deformation is stopped when the residual stress release rate reaches 68%, resulting in a dislocation density of 1.3 × 10⁻⁶. 14 m -2 A uniform dislocation network.

[0082] Low-temperature aging: The pre-stretched profile is placed in an air-circulating oven and heated to 110℃ at a rate of 5.5℃ / min. It is then kept at this temperature for 2.5 hours under nitrogen protection to form a high-density GP region with a size of 3.5-4.5nm.

[0083] Secondary stretching: The profiles that have undergone low-temperature aging are subjected to a secondary stretching of 10%.

[0084] High-temperature aging: The profile after secondary stretching is placed in a vacuum aging furnace with a vacuum degree of 0.07 Pa and heated to 155℃ at a rate of 4.5℃ / min. The temperature is monitored by infrared thermography, and the temperature difference is controlled within ±1.2℃. The temperature is maintained for 10 hours to promote the transformation of the GP region into the 10-14nm nanoscale η' phase, and the η' phase is uniformly precipitated on the dislocation lines inside the grain.

[0085] Final stretching: The profile after high-temperature aging is subjected to a final stretch of 5.5%.

[0086] The reinforced profile is then machined and surface-treated to obtain a high-strength, corrosion-resistant aluminum alloy finished product.

[0087] This embodiment ensures the uniformity and purity of the composition by precisely controlling the process parameters at each stage, especially during the raw material preparation and smelting stages. Homogenization treatment effectively improves the microstructure defects of the ingot. Extrusion molding and solution quenching lay a good foundation for the material properties. In the strengthening treatment, the high-density dislocation network introduced by pre-stretching, along with the synergistic effect of double-stage aging and multiple stretching, promotes the uniform and dispersed precipitation of the nanoscale η' phase, inhibits the formation of coarse phases, and optimizes the grain boundary structure. The final aluminum alloy product exhibits excellent strength, toughness, and corrosion resistance, with stable overall performance, making it suitable for various high-end industrial fields.

[0088] Comparative Example

[0089] This comparative example uses different process parameters than the above embodiments to compare and analyze the impact of the process on the properties of aluminum alloys. The specific steps are as follows:

[0090] Raw material preparation and smelting: The raw materials were prepared according to the following chemical composition: Si content 0.08%, Fe content 0.15%, Cu addition 0.28%, Mn addition 0.05%, Mg ratio 2.00%, Cr setting 0.015%, Zn adjustment 5.7%, and Ti addition 0.025%. The materials were smelted in a graphite crucible at 710℃. The order of alloying elements was randomized. The stirring rate was 250 r / min, the stirring time was 10 min, and the degassing argon gas blowing rate was 0.3 L / min for 15 min. After slag removal, the materials were cast into Φ120 mm ingots.

[0091] The ingots were homogenized by placing them in a box-type resistance furnace at a heating rate of 80℃ / h. After heating to 450℃, the temperature was held for 6 hours, and then cooled to 160℃ with the furnace at a rate of 40℃ / h. The ingots were then removed from the furnace and allowed to cool naturally to room temperature without natural aging.

[0092] Extrusion molding was carried out using a horizontal extruder to extrude profiles with a cross-section of 50mm×10mm. The ingot heating temperature was 410℃, the die preheated to 380℃, the extrusion rate was 8m / min, and no water spray cooling was performed during the extrusion process. The material was air-cooled to room temperature, and the extrusion ratio was 15:1.

[0093] Solution hardening treatment involves placing the profile in a continuous solution furnace and holding it at 460℃ for 0.5 hours. After holding, it is quenched with deionized water at 35℃ with a water flow rate of 8 m / s and a core cooling rate of 150℃ / s. The water film on the surface of the profile falls off within 40 seconds after quenching.

[0094] Pre-stretching: The solution-quenched profile is pre-stretched by 0.5% at a deformation rate of 4 mm / min, stopping when the residual stress release rate reaches 40%, with a dislocation density of 5 × 10⁻⁶. 13 m -2 .

[0095] Low-temperature aging: The pre-stretched profile is placed in a regular oven and heated to 100°C at a rate of 10°C / min. Without inert gas protection, it is held for 2 hours to form a GP region with a size of 6-8nm.

[0096] Secondary stretching: No secondary stretching was performed.

[0097] High-temperature aging: The profile was placed in a vacuum aging furnace with a vacuum degree of 0.2 Pa and heated to 165°C at a rate of 6°C / min. Temperature uniformity was not monitored and the temperature difference reached ±5°C. After holding for 8 hours, the GP region was transformed into the η' phase of 20-30 nm and the distribution was uneven.

[0098] Final stretching: The profile after high-temperature aging is subjected to a final stretch of 3%.

[0099] The reinforced profile is then subjected to simple machining and surface treatment to obtain the finished product.

[0100] The comparative example used unreasonable process parameters in the control of raw material composition, smelting process, homogenization treatment, extrusion molding, solution quenching and strengthening treatment, resulting in poor performance of the prepared aluminum alloy product. Inaccurate composition control and improper process parameter settings led to uneven internal structure of the material, coarse and disordered precipitation of strengthening phases, insufficient release of residual stress, and unoptimized grain boundary structure. Ultimately, the material could not reach the level of the example in terms of strength, toughness and corrosion resistance.

[0101]

[0102]

[0103] As can be seen from the comparison table above, the embodiments strictly follow the chemical composition requirements of 7-series aluminum alloys in the patent (Si < 0.07%, Fe ≤ 0.12%, Cu 0.3-0.35%, etc.), and the content of each element is within the optimized range; the process is controlled according to the patented technical parameters, and the parameters of the melting, homogenization, extrusion, and solution quenching stages are reasonable, and the strengthening treatment introduces ≥10 through 1-3% pre-stretching. 14 m -2 The dislocation network, combined with two-stage aging and secondary and final stretching, promotes the uniform precipitation of the 5-15nm nanoscale η' phase, ensuring a balance between the material's strength, toughness, and corrosion resistance. In contrast, the chemical composition of the comparative example deviated from the requirements (excessive Si and Fe, insufficient Cu, Mg, and Zn, etc.), and the parameters of each process deviated from the patented technical standards. For example, the melting temperature was low, the stirring was insufficient, the homogenization time was short, the extrusion ratio was small, the solution cooling rate was insufficient, the pre-stretching amount was insufficient and the secondary stretching was missing, and the aging parameters were unreasonable, resulting in a coarse η' phase (20-30nm). The final performance was far lower than that of the example. It can be seen that strictly controlling the chemical composition and process parameters specified in the patent is the key to achieving high strength and corrosion resistance of aluminum alloys.

[0104] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for strengthening high-strength, corrosion-resistant aluminum alloys, characterized in that, The method includes the following steps: 7-series aluminum alloy profiles that have undergone solution quenching are subjected to a 1-3% pre-stretching treatment to introduce a dislocation density ≥10. 14 m -2 The dislocation network of the 7-series aluminum alloy, wherein the composition satisfies Si < 0.07%, Fe ≤ 0.12%, Cu 0.3-0.35%, Mn 0.07-0.17%, Mg 2.10-2.40%, Cr 0.003-0.012%, Zn 5.9-6.3%, and Ti 0.003-0.020%; The pre-stretched profile is subjected to low-temperature aging at 110℃ for 2.5 hours to form a high-density GP zone; The profiles that have undergone low-temperature aging are subjected to a secondary stretching of 10%. The profile after secondary stretching was subjected to high-temperature aging at 155℃ for 10 hours to promote the transformation of the GP region into the 5-15nm nanoscale η' phase. The profiles after high-temperature aging are subjected to a final stretch of 4-6%.

2. The strengthening method for a high-strength, corrosion-resistant aluminum alloy according to claim 1, characterized in that, The pre-stretching treatment is achieved through unidirectional plastic deformation along the length of the profile, with the deformation rate controlled at 5-10 mm / min. Stress changes are monitored in real time during the deformation process, and stretching is stopped when the residual stress release rate reaches 60-70%, forming a uniformly distributed dislocation network configuration.

3. The strengthening method for a high-strength, corrosion-resistant aluminum alloy according to claim 1, characterized in that, The low-temperature aging is carried out in an air-circulating oven with a heating rate of 5-8℃ / min. After reaching 110℃, the temperature is kept constant. Inert gas protection is used during the aging process to avoid surface oxidation. The size of the GP region is controlled at 2-5nm.

4. The strengthening method for a high-strength, corrosion-resistant aluminum alloy according to claim 1, characterized in that, The high-temperature aging is carried out in a vacuum aging furnace with a vacuum degree ≥0.1Pa and a heating rate of 3-5℃ / min. During the 155℃ constant temperature stage, the internal temperature uniformity of the profile is monitored in real time by infrared thermography, and the temperature difference is controlled within ±2℃. The η' phase is uniformly precipitated on the dislocation lines inside the grain.

5. A preparation process for a high-strength, corrosion-resistant aluminum alloy, characterized in that, The preparation process includes the following steps: The intermediate elements were prepared and smelted according to the composition of Si < 0.07%, Fe ≤ 0.12%, Cu 0.3-0.35%, Mn 0.07-0.17%, Mg 2.10-2.40%, Cr 0.003-0.012%, Zn 5.9-6.3%, and Ti 0.003-0.020%, and the resulting ingots were cast after slag and degassing. Homogenize the ingots; The homogenized ingot is extruded into profiles; The profiles are subjected to solution quenching treatment; The quenched profiles are subjected to strengthening treatments in sequence, including 1-3% pre-stretching, low-temperature aging at 110℃ for 2.5h, 10% secondary stretching, high-temperature aging at 155℃ for 10h, and 4-6% final stretching. The reinforced profiles are then machined and surface-treated to obtain the finished product.

6. The preparation process of a high-strength corrosion-resistant aluminum alloy according to claim 5, characterized in that, The melting is carried out in a graphite crucible at a temperature of 720-750℃. The alloying elements are added in the order of Zn, Mg, Cu, Mn, Cr, Ti, and Si. The stirring rate is 300-500 r / min and the stirring time is 15-20 min. Argon gas is used for degassing at a rate of 0.5-1 L / min for 20-30 min.

7. The preparation process of a high-strength corrosion-resistant aluminum alloy according to claim 5, characterized in that, The homogenization process is carried out in a box-type resistance furnace with a heating rate of 100-150℃ / h. After holding at 460-480℃ for 8-12 hours, the furnace is cooled to below 150℃ at a rate of 50-80℃ / h. After being removed from the furnace, the furnace is allowed to cool naturally to room temperature, followed by natural aging for 24-48 hours.

8. The preparation process of a high-strength corrosion-resistant aluminum alloy according to claim 5, characterized in that, The extrusion molding process uses a horizontal extruder. The ingot heating temperature is 420-450℃, the die preheating temperature is 400-430℃, and the extrusion rate is controlled by a servo system at 10-15m / min. During the extrusion process, water spray is used to cool the profile surface. After cooling to 200-250℃, it is air-cooled to room temperature. The extrusion ratio is 20-30:

1.

9. The preparation process of a high-strength corrosion-resistant aluminum alloy according to claim 5, characterized in that, The solution treatment is carried out in a continuous solution furnace, held at 470-490℃ for 1-2 hours, and immediately after the holding is completed, water quenching is performed. The quenching medium is deionized water at 20-30℃, and the water flow rate is 10-15m / s, so that the cooling rate of the core of the profile is ≥200℃ / s. After quenching, the water film on the surface of the profile falls off within 30s.

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