A heat treatment process for reducing the fatigue crack growth rate of aluminium-copper-magnesium alloys

Abstract

The present application belongs to the technical field of aluminum alloy heat treatment process, and in particular to a heat treatment method for obtaining aluminum-copper-magnesium alloy with ultra-low fatigue crack growth rate. The method comprises the following steps: step one, after solid solution heat preservation of the aluminum alloy sample, rapidly perform hot rolling, and immediately perform cryogenic quenching after hot rolling; step two, perform pre-aging treatment of the sample obtained in step one with appropriate parameters; step three, perform cryogenic deformation of the sample obtained in step two to obtain a cryogenic deformation sample; step four, perform aging treatment of the cryogenic deformation sample obtained in step three to obtain a finished product. The aluminum alloy prepared by the process has ultra-low fatigue crack growth rate and excellent mechanical strength. The process is simple and controllable, the obtained product has excellent performance, and is convenient for large-scale industrial application.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy heat treatment technology, specifically a heat treatment method for obtaining aluminum-copper-magnesium alloys with ultra-low fatigue crack propagation rate. Background Technology

[0002] Aluminum alloys are crucial materials in the aerospace field. Among them, Al-Cu-Mg alloys possess characteristics such as lightweight yet high strength, high toughness, high damage tolerance, good fatigue resistance, excellent temperature resistance, low production cost, and easy processing, making them widely used in aircraft skins, frames, panels, and spacecraft main structural components. However, with the challenges posed by various new materials and the increasing demands, the performance of traditionally processed aluminum alloys can no longer meet the requirements.

[0003] Fatigue performance is a key property of aerospace aluminum alloys. Fatigue and fracture are significant factors leading to the failure of industrial structural components, and the fatigue performance of commercial aluminum-copper-magnesium alloys still urgently needs improvement to meet the evolving needs of the industry.

[0004] Traditional methods for improving the properties of aluminum alloys mainly include microalloying, powder metallurgy, spray forming, and various aging processes. In recent years, large deformation technologies such as high-pressure torsion and equal-channel angular extrusion have also emerged, improving alloy properties by refining the alloy's microstructure. However, these technologies still suffer from drawbacks such as limited sample size, high cost, and difficulty in operation. In contrast, thermomechanical treatment is more economical, has a simpler process, and is easier for continuous production. Thermomechanical treatment is a processing technology that combines plastic deformation with heat treatment during machining, comprehensively improving the overall properties of the alloy through deformation strengthening and precipitation strengthening.

[0005] Cryogenic asymmetric rolling combines the advantages of both cryogenic rolling and asymmetric rolling. During cryogenic rolling, the cryogenic environment effectively suppresses the dynamic recovery of the alloy, thus preserving the high-density dislocations generated during deformation. Compared to conventional rolling, asymmetric rolling introduces shear strain into the alloy, which is beneficial for grain rotation and refinement, altering the material's texture configuration and causing shear texture to appear within the material, thus refining the grains.

[0006] Previous studies, such as patent CN201710059216.9, have attempted to suppress crack formation by using continuous hot rolling treatment + deep cryogenic deformation + artificial aging treatment, and this technology has achieved certain results. Meanwhile, Ren Jie et al., in their paper "The Influence of Novel Thermomechanical Treatment on the Microstructure and Properties of 2E12 Aluminum Alloy," mentioned that applying solution treatment + aging + cold rolling deformation + natural aging to 2E12 alloy cold-rolled sheets can achieve the desired crack structure when ΔK is 10 MPa·m. 1 / 2 At that time, the fatigue crack propagation rate was 6.74 × 10⁻⁶. -52E12 alloy with a capacity of mm / cycle. Summary of the Invention:

[0007] In response to the shortcomings of existing technologies, and in conjunction with a series of innovative explorations in thermomechanical treatment technology by our research group in recent times (such as patent CN201710059216.9 and the paper "The Influence of Novel Thermomechanical Treatment on the Microstructure and Properties of 2E12 Aluminum Alloy"), this invention proposes a heat treatment method to further reduce the fatigue crack propagation rate of products while ensuring reasonable mechanical strength.

[0008] This invention discloses a heat treatment process for reducing the fatigue crack propagation rate of aluminum-copper-magnesium alloys. The aluminum-copper-magnesium alloy comprises the following elements and their contents, by mass percentage:

[0009] Cu 2.0-6.0%, preferably 3.0-5.0%, more preferably 3.8-4.2%, and even more preferably 4.15-4.2%;

[0010] Mg 0.5-2.0%, preferably 0.8-1.7%, more preferably 1.1-1.4%, and even more preferably 1.25-1.35% or 1.1-1.15%;

[0011] Mn 0.1-2.0%, preferably 0.4-1.3%, more preferably 0.6-0.9%, and even more preferably 0.85-0.9% or 0.68-0.72%;

[0012] The margin is Al.

[0013] This invention discloses a heat treatment process for reducing the fatigue crack propagation rate of aluminum-copper-magnesium alloys. The process involves heating the original aluminum-copper-magnesium alloy sample to the solution temperature in a resistance furnace and holding it at that temperature for a period of time. Then, the sample is hot-rolled and quenched in cold water. After low-temperature pre-aging for a period of time, it is subjected to cryogenic asymmetric rolling. Finally, the sample is subjected to final aging treatment after cryogenic rolling.

[0014] This invention discloses a heat treatment process for reducing the fatigue crack propagation rate of aluminum-copper-magnesium alloys, the specific steps of which are as follows:

[0015] Step 1: Solution hot rolling continuous treatment

[0016] The sample is heated to the solution temperature in an electric resistance furnace and held for a period of time, then quickly transferred to a rolling mill for hot rolling, followed by quenching with cold water; the solution temperature is between 480℃ and 500℃, and the holding time is between 30 min and 90 min; the quenching transfer time should be ≤5 s; after solution holding, the sample is cooled in the furnace or air-cooled to 455℃-475℃ before rolling, ensuring that the final rolling temperature is greater than 445℃; the hot rolling deformation is 5%-55%.

[0017] Step 2: Low-temperature pre-aging treatment

[0018] The alloy sample obtained in the first step is pre-aged in a hot air circulating furnace; the holding temperature for the second step of pre-aging should be between 60℃ and 100℃, and the holding time should be between 4h and 12h.

[0019] Step 3: Cryogenic Asynchronous Rolling

[0020] The alloy sample obtained in the second step is subjected to asynchronous rolling at ultra-low temperature, wherein the cryogenic asynchronous rolling temperature should be ≤-120℃, the rate ratio should be greater than 1.1, and the deformation amount should be 5%-35%.

[0021] Step 4: Final Validity Processing

[0022] The sample obtained in the third step is subjected to final aging treatment in a hot air circulating furnace; the holding temperature for the fourth step of final aging should be between 80℃ and 120℃, and the holding time should be between 4h and 16h.

[0023] The preferred solution temperature is 490℃-500℃, the holding time is 60min-80min, and the quenching transfer time is 3-5s.

[0024] The preferred initial rolling temperature is 460℃-470℃, the final rolling temperature is 445℃-450℃, and the hot rolling deformation is 15%-35%. More preferably, it is 15%-20%.

[0025] This invention discloses a heat treatment process for reducing the fatigue crack propagation rate of aluminum-copper-magnesium alloys, wherein the second step of pre-aging temperature is 70℃-80℃ and the holding time is 6h-10h.

[0026] Preferably, the pre-aging temperature in the second step is 74℃-76℃, and the holding time is 7h-9h, more preferably 7-7.5h. In this invention, strictly controlling the pre-aging temperature and time in the second step is to better regulate the formation and retention of clusters. A large number of large-sized clusters have a greater hindering effect on moving dislocations, but they are also more likely to cause stress concentration. However, clusters that are too small are difficult to repair microcracks in a timely manner. Therefore, both of these situations need to be avoided as much as possible.

[0027] The present invention discloses a heat treatment process for reducing the fatigue crack propagation rate of aluminum-copper-magnesium alloys. The rolling temperature of the third step, cryogenic asynchronous rolling, is -200℃ to 120℃, the rate ratio is between 1.1 and 1.5, and the deformation is 5% to 35%.

[0028] The preferred cryogenic asynchronous rolling temperature is -190℃ to -160℃, the speed ratio is 1.1-1.3, and the rolling deformation is 10%-20%.

[0029] The present invention discloses a heat treatment process for reducing the fatigue crack propagation rate of aluminum-copper-magnesium alloys. The holding temperature of the fourth step final aging should be between 90℃ and 110℃, and the holding time should be between 5h and 10h.

[0030] This invention discloses a heat treatment process for reducing the fatigue crack propagation rate of aluminum-copper-magnesium alloys. When the alloy composition is Al-4.2Cu-1.3Mg-0.9Mn (mass fraction%), the process involves first solution treatment at 500℃ for 1 hour, followed by hot rolling at 470℃, with a final rolling temperature of 450℃ (15% hot rolling deformation). After hot rolling, the alloy is water-quenched within 5 seconds. The resulting sample undergoes a low-temperature pre-aging treatment at 75℃ for 7 hours in a hot blast furnace, followed by immersion in a cryogenic medium for 10 minutes to lower the temperature to -170℃ for cryogenic asynchronous rolling at a rate ratio of 1.1 and a deformation of 10%. The sample after cryogenic asynchronous rolling undergoes a final aging treatment at 100℃ for 6 hours in a hot blast furnace. The fatigue crack propagation rate of the resulting product is significantly lower than that of existing technologies.

[0031] This invention discloses a heat treatment process for reducing the fatigue crack propagation rate of aluminum-copper-magnesium alloys. When the alloy composition is Al-4.2Cu-1.1Mg-0.7Mn (mass fraction%), the process involves first solution treatment at 490℃ for 1 hour, followed by hot rolling at 460℃, with a final rolling temperature of 440℃ (20% hot rolling deformation). After hot rolling, the alloy is water-quenched within 5 seconds. The resulting sample undergoes a low-temperature pre-aging treatment at 75℃ for 7 hours in a hot blast furnace, followed by immersion in a cryogenic medium for 10 minutes to lower the temperature to -170℃ for cryogenic asynchronous rolling at a rate ratio of 1.3 and a deformation of 10%. The sample after cryogenic asynchronous rolling undergoes a final aging treatment at 100℃ for 6 hours in a hot blast furnace. The fatigue crack propagation rate of the resulting product is significantly lower than that of existing technologies.

[0032] The outstanding advantages of this invention are:

[0033] This invention incorporates a short-duration, low-temperature artificial pre-aging treatment between solution hot rolling and cryogenic asymmetric rolling. On one hand, this process induces some solute atoms to desolve from the supersaturated solid solution. Some of these atoms are captured by vacancies in the material and agglomerate, thus completing the pre-precipitation of atomic clusters. The other part forms appropriately sized micro-precipitates. These products not only hinder dislocation movement during subsequent plastic deformation, ensuring uniform dislocation distribution in the alloy, but also provide precipitation strengthening during artificial aging. On the other hand, the pre-aging treatment repairs material damage caused by deformation in the previous stage, alleviating stress concentration in the material, which is beneficial for deformation during subsequent processing.

[0034] According to the dislocation reverse slip theory, during fatigue, dislocations within the alloy move back and forth under the applied load, easily accumulating at inaccessible precipitates or grain boundaries, causing stress concentration and negatively impacting the material's fatigue performance. Pre-aging can generate numerous moderately sized and uniformly distributed Cu-Mg atomic clusters within the alloy. These clusters can be easily passed through by moving dislocations, while some clusters are broken down and decomposed, preventing their influence during dislocation reverse slip. This mitigates stress concentration to some extent, significantly reducing ductile damage to crack tips and improving the alloy's fatigue performance. When atomic clusters are large, they significantly impede dislocation movement, easily forming stress concentration zones around them, leading to crack initiation and propagation. Conversely, smaller atomic clusters may reduce stress concentration effects, thus decreasing the tendency for crack initiation and propagation. Furthermore, smaller atomic clusters allow dislocations to pass through them more easily, reducing their restrictive effect on dislocation movement.

[0035] The alloy after solution hot rolling contains numerous dislocation defects and supersaturated solid solution structures. Studies have found that direct cryogenic asynchronous rolling may lead to excessive large dislocation entanglements and the storage of more recrystallization energy. These dislocation structures are more prone to recovery recrystallization during subsequent final aging treatment, forming a large number of stable precipitates and large clusters, and may also cause cracking during cryogenic deformation. Setting a low-temperature artificial pre-aging process between solution hot rolling and cryogenic asynchronous rolling can, on the one hand, consume some dislocations and release stored energy, which is beneficial to the uniform distribution of dislocation structures; on the other hand, it can pre-precipitate atomic clusters. These pre-precipitated atoms can agglomerate into appropriately sized atomic clusters during subsequent cryogenic deformation and artificial final aging, which helps to reduce the fatigue crack propagation rate. The parameters of pre-aging have a significant impact on the effect of pre-aging: if the pre-aging temperature is too low or the time is too short, the aging result will be insignificant, resulting in a large number of precipitates and a small number of clusters in the final alloy, which will have limited effect on improving the fatigue performance of the material, especially the reduction in fatigue crack propagation rate. If the pre-aging temperature is too high or the time is too long, the dislocation structure in the pre-aged alloy will be significantly reduced and fine precipitates will appear. These precipitates will grow into large precipitates after subsequent deformation and final aging treatment. These precipitates have a greater hindering effect on moving dislocations and are more likely to cause stress concentration, thereby leading to fatigue cracking of the material. Attached image description:

[0036] Figure 1 This is a comparison chart of fatigue crack propagation rates in Examples 1, 2, and 3 and Comparative Examples 2, 3, and 4 of the present invention. Detailed Implementation

[0037] Example 1:

[0038] The original sample was a 7mm thick plate with an alloy composition of Al-4.2Cu-1.3Mg-0.9Mn (mass fraction %). First, it underwent solution treatment at 500℃ for 1 hour, followed by hot rolling at 470℃, with a final rolling temperature of 450℃ (15% hot rolling deformation). After hot rolling, it was water-quenched within 5 seconds. The resulting sample underwent low-temperature pre-aging treatment at 75℃ for 7 hours in a hot blast furnace. Then, the sample was immersed in a cryogenic medium for 10 minutes to lower its temperature to -170℃ for cryogenic asynchronous rolling at a rate ratio of 1.1 and a deformation of 10%. After cryogenic asynchronous rolling, the sample underwent final aging treatment at 100℃ for 6 hours in a hot blast furnace. The alloy treated in this example exhibited a tensile strength of 491.8 MPa, a yield strength of 404.9 MPa, and an elongation of 12.7%. Fatigue resistance is shown in [reference needed]. Figure 1 The product obtained in this embodiment was tested for fatigue crack propagation rate under the conditions of 20℃ atmospheric environment, experimental loading waveform of sine wave, frequency of 10Hz, and stress ratio of 0.1; its fatigue crack propagation rate is: when ΔK is 10MPa·m 1 / 2 At that time, the fatigue crack propagation rate was 1.7 × 10⁻⁶. -5 mm / cycle, when ΔK is 33MPa·m 1 / 2 At this point, fatigue cracks enter a high-speed propagation stage.

[0039] Example 2:

[0040] The original sample was a 7mm thick plate with an alloy composition of Al-4.0Cu-1.2Mg-0.8Mn (mass fraction %). First, it underwent solution treatment at 495℃ for 1 hour, followed by hot rolling at 465℃, with a final rolling temperature of 445℃ (20% hot rolling deformation). After hot rolling, it was water-quenched within 5 seconds. The resulting sample underwent low-temperature pre-aging treatment at 75℃ for 8 hours in a hot blast furnace. Then, the sample was immersed in a cryogenic medium for 10 minutes to lower its temperature to -170℃ for cryogenic asynchronous rolling at a rate ratio of 1.2 and a deformation of 10%. After cryogenic asynchronous rolling, the sample underwent final aging treatment at 100℃ for 6 hours in a hot blast furnace. The alloy treated in this example exhibited a tensile strength of 497.8 MPa, a yield strength of 413.4 MPa, and an elongation of 12.5 MPa. Fatigue resistance is shown in [reference needed]. Figure 1 The product obtained in this embodiment was tested for fatigue crack propagation rate under the conditions of 20℃ atmospheric environment, experimental loading waveform of sine wave, frequency of 10Hz, and stress ratio of 0.1; its fatigue crack propagation rate is: when ΔK is 10MPa·m 1 / 2 At that time, the fatigue crack propagation rate was 5.2 × 10⁻⁶. -5 mm / cycle, when ΔK is 29MPa·m 1 / 2At this point, fatigue cracks enter a high-speed propagation stage.

[0041] Example 3:

[0042] The original sample was a 7mm thick plate with an alloy composition of Al-3.9Cu-1.1Mg-0.7Mn (mass fraction %). First, it underwent solution treatment at 490℃ for 1 hour, followed by hot rolling at 460℃, with a final rolling temperature of 440℃ (15% hot rolling deformation). After hot rolling, it was water-quenched within 5 seconds. The resulting sample underwent low-temperature pre-aging treatment at 75℃ for 9 hours in a hot blast furnace. Then, the sample was immersed in a cryogenic medium for 10 minutes to lower its temperature to -170℃ for cryogenic asynchronous rolling at a rate ratio of 1.3 and a deformation of 15%. After cryogenic asynchronous rolling, the sample underwent final aging treatment at 100℃ for 6 hours in a hot blast furnace. The alloy treated in this example exhibited a tensile strength of 511.2 MPa, a yield strength of 440.8 MPa, and an elongation of 11.5%. Fatigue resistance properties are described in [reference needed]. Figure 1 The product obtained in this embodiment was tested for fatigue crack propagation rate under the conditions of 20℃ atmospheric environment, experimental loading waveform of sine wave, frequency of 10Hz, and stress ratio of 0.1; its fatigue crack propagation rate is: when ΔK is 10MPa·m 1 / 2 At that time, the fatigue crack propagation rate was 5.6 × 10⁻⁶. -5 mm / cycle, when ΔK is 30MPa·m 1 / 2 At this point, fatigue cracks enter a high-speed propagation stage.

[0043] Example 4:

[0044] The original sample was a 7mm thick plate with an alloy composition of Al-4.2Cu-1.1Mg-0.7Mn (mass fraction %). First, it underwent solution treatment at 490℃ for 1 hour, followed by hot rolling at 460℃, with a final rolling temperature of 440℃ (20% hot rolling deformation). After hot rolling, it was water-quenched within 5 seconds. The resulting sample underwent low-temperature pre-aging treatment at 70℃ for 7 hours in a hot blast furnace. Then, the sample was immersed in a cryogenic medium for 10 minutes to lower its temperature to -170℃ for cryogenic asynchronous rolling at a rate ratio of 1.3 and a deformation of 10%. After cryogenic asynchronous rolling, the sample underwent final aging treatment at 100℃ for 6 hours in a hot blast furnace. The alloy treated in this example exhibited a tensile strength of 508.2 MPa, a yield strength of 424.8 MPa, and an elongation of 11.9%. The product obtained in this embodiment was tested for fatigue crack propagation rate under the conditions of 20℃ atmospheric environment, experimental loading waveform of sine wave, frequency of 10Hz, and stress ratio of 0.1; its fatigue crack propagation rate is: when ΔK is 10MPa·m 1 / 2 At that time, the fatigue crack propagation rate was 3.3 × 10⁻⁶.-5 mm / cycle, when ΔK is 31MPa·m 1 / 2 At this point, fatigue cracks enter a high-speed propagation stage.

[0045] Example 5:

[0046] The original sample was a 7mm thick plate with an alloy composition of Al4.2Cu-1.1Mg-0.7Mn (mass fraction %). First, it underwent solution treatment at 490℃ for 1 hour, followed by hot rolling at 460℃, with a final rolling temperature of 440℃ (20% hot rolling deformation). After hot rolling, it was water-quenched within 5 seconds. The resulting sample underwent low-temperature pre-aging treatment at 80℃ for 7 hours in a hot blast furnace. Then, the sample was immersed in a cryogenic medium for 10 minutes to lower its temperature to -170℃ for cryogenic asynchronous rolling at a rate ratio of 1.3 and a deformation of 10%. After cryogenic asynchronous rolling, the sample underwent final aging treatment at 100℃ for 6 hours in a hot blast furnace. The alloy treated in this example exhibited a tensile strength of 512.6 MPa, a yield strength of 433.8 MPa, and an elongation of 11.1%. The product obtained in this embodiment was tested for fatigue crack propagation rate under the conditions of 20℃ atmospheric environment, experimental loading waveform of sine wave, frequency of 10Hz, and stress ratio of 0.1; its fatigue crack propagation rate is: when ΔK is 10MPa·m 1 / 2 At that time, the fatigue crack propagation rate was 3.9 × 10⁻⁶. -5 mm / cycle, when ΔK is 30MPa·m 1 / 2 At this point, fatigue cracks enter a high-speed propagation stage.

[0047] Example 6:

[0048] The original sample was a 7mm thick plate with an alloy composition of Al4.2Cu-1.1Mg-0.7Mn (mass fraction %). First, it underwent solution treatment at 490℃ for 1 hour, followed by hot rolling at 460℃, with a final rolling temperature of 440℃ (20% hot rolling deformation). After hot rolling, it was water-quenched within 5 seconds. The resulting sample underwent low-temperature pre-aging treatment at 75℃ for 7 hours in a hot blast furnace. Then, the sample was immersed in a cryogenic medium for 10 minutes to lower its temperature to -170℃ for cryogenic asynchronous rolling at a rate ratio of 1.3 and a deformation of 10%. After cryogenic asynchronous rolling, the sample underwent final aging treatment at 100℃ for 6 hours in a hot blast furnace. The alloy treated in this example exhibited a tensile strength of 518.5 MPa, a yield strength of 441.8 MPa, and an elongation of 10.9%. The product obtained in this embodiment was tested for fatigue crack propagation rate under the conditions of 20℃ atmospheric environment, experimental loading waveform of sine wave, frequency of 10Hz, and stress ratio of 0.1; its fatigue crack propagation rate is: when ΔK is 10MPa·m 1 / 2At that time, the fatigue crack propagation rate was 1.9 × 10⁻⁶. -5 mm / cycle, when ΔK is 34MPa·m 1 / 2 At this point, fatigue cracks enter a high-speed propagation stage.

[0049] Comparative Example 1:

[0050] The original sample was a 7mm thick plate with an alloy composition of Al-4.2Cu-1.3Mg-0.9Mn (mass fraction %). First, it underwent solution treatment at 495℃ for 1 hour, followed by water quenching within 5 seconds. Then, the sample was rolled at room temperature under atmospheric conditions with a deformation of 5%. The deformed sample was then subjected to final aging treatment at atmospheric and room temperature for 15 days. The alloy treated in this comparative example exhibited a tensile strength of 405.8 MPa, a yield strength of 319.6 MPa, and an elongation of 23.8%. The product obtained in this example was tested for fatigue crack propagation rate under the conditions of 20℃ atmospheric environment, a sinusoidal loading waveform at a frequency of 10Hz, and a stress ratio of 0.1; its fatigue crack propagation rate was: when ΔK is 10 MPa·m 1 / 2 At that time, the fatigue crack propagation rate was 9.6 × 10⁻⁶. -5 mm / cycle, when ΔK is 25MPa·m 1 / 2 At this point, fatigue cracks enter a high-speed propagation stage.

[0051] Comparative Example 2

[0052] The original sample was a 7mm thick plate with an alloy composition of Al-4.2Cu-1.3Mg-0.9Mn (mass fraction %). It was first solution treated at 495℃ for 1 hour, followed by water quenching within 5 seconds. Then, the sample underwent final aging treatment at 190℃ for 12 hours in a hot air circulating furnace. The alloy after this comparative treatment exhibited a tensile strength of 442.4 MPa, a yield strength of 349.7 MPa, and an elongation of 12.8%. Fatigue resistance is shown in [reference needed]. Figure 1 The product obtained in this embodiment was tested for fatigue crack propagation rate under the conditions of 20℃ atmospheric environment, experimental loading waveform of sine wave, frequency of 10Hz, and stress ratio of 0.1; its fatigue crack propagation rate is: when ΔK is 10MPa·m 1 / 2 At that time, the fatigue crack propagation rate was 1.5 × 10⁻⁶. -4 mm / cycle, when ΔK is 24MPa·m 1 / 2 At this point, fatigue cracks enter a high-speed propagation stage.

[0053] Comparative Example 3

[0054] The original sample was a 7mm thick plate with an alloy composition of Al-4.2Cu-1.3Mg-0.9Mn (mass fraction %). First, it underwent solution treatment at 500℃ for 1 hour, followed by hot rolling at 470℃, with a final rolling temperature of 450℃ (15% hot rolling deformation). After hot rolling, it was water-quenched within 5 seconds. The resulting sample underwent low-temperature pre-aging treatment at 50℃ for 3 hours in a hot blast furnace. Then, the sample was immersed in a cryogenic medium for 10 minutes to lower its temperature to -170℃ for cryogenic asynchronous rolling at a rate ratio of 1.1 and a deformation of 10%. After cryogenic asynchronous rolling, the sample underwent final aging treatment at 100℃ for 6 hours in a hot blast furnace. The alloy treated in this example exhibited a tensile strength of 474.2 MPa, a yield strength of 384.5 MPa, and an elongation of 12.2%. Fatigue resistance is shown in [reference needed]. Figure 1 The product obtained in this embodiment was tested for fatigue crack propagation rate under the conditions of 20℃ atmospheric environment, experimental loading waveform of sine wave, frequency of 10Hz, and stress ratio of 0.1; its fatigue crack propagation rate is: when ΔK is 10MPa·m 1 / 2 At that time, the fatigue crack propagation rate was 1.7 × 10⁻⁶. -4 mm / cycle, when ΔK is 21MPa·m 1 / 2 At this point, fatigue cracks enter a high-speed propagation stage.

[0055] Comparative Example 4

[0056] The original sample was a 7mm thick plate with an alloy composition of Al-4.2Cu-1.3Mg-0.9Mn (mass fraction %). First, it underwent solution treatment at 500℃ for 1 hour, followed by hot rolling at 470℃, with a final rolling temperature of 450℃ (10% hot rolling deformation). After hot rolling, it was water-quenched within 5 seconds. The resulting sample underwent low-temperature pre-aging treatment at 110℃ for 12 hours in a hot blast furnace. Then, the sample was immersed in a cryogenic medium for 10 minutes to lower its temperature to -170℃ for cryogenic asynchronous rolling at a rate ratio of 1.1 and a deformation of 15%. After cryogenic asynchronous rolling, the sample underwent final aging treatment at 100℃ for 6 hours in a hot blast furnace. The alloy treated in this example exhibited a tensile strength of 481.1 MPa, a yield strength of 396.3 MPa, and an elongation of 11.8%. Fatigue resistance is shown in [reference needed]. Figure 1 The product obtained in this embodiment was tested for fatigue crack propagation rate under the conditions of 20℃ atmospheric environment, experimental loading waveform of sine wave, frequency of 10Hz, and stress ratio of 0.1; its fatigue crack propagation rate is: when ΔK is 10MPa·m 1 / 2 At that time, the fatigue crack propagation rate was 1.9 × 10⁻⁶. -4 mm / cycle, when ΔK is 24MPa·m 1 / 2At this point, fatigue cracks enter a high-speed propagation stage.

[0057] Comparative Example 5

[0058] The original sample was a 7mm thick plate with an alloy composition of Al-4.2Cu-1.3Mg-0.9Mn (mass fraction %). First, it underwent solution treatment at 500℃ for 1 hour, followed by hot rolling at 470℃, with a final rolling temperature of 450℃ (20% hot rolling deformation). After hot rolling, it was water-quenched within 5 seconds. The resulting sample underwent low-temperature pre-aging treatment at 55℃ for 4 hours in a hot blast furnace. Then, the sample was immersed in a cryogenic medium for 10 minutes to lower its temperature to -170℃ for cryogenic asynchronous rolling at a rate ratio of 1.1 and a deformation of 15%. After cryogenic asynchronous rolling, the sample underwent final aging treatment at 100℃ for 6 hours in a hot blast furnace. The alloy treated in this example exhibited a tensile strength of 517.3 MPa, a yield strength of 455.2 MPa, and an elongation of 9.9%. The product obtained in this embodiment was tested for fatigue crack propagation rate under the conditions of 20℃ atmospheric environment, experimental loading waveform of sine wave, frequency of 10Hz, and stress ratio of 0.1; its fatigue crack propagation rate is: when ΔK is 10MPa·m 1 / 2 At that time, the fatigue crack propagation rate was 2.8 × 10⁻⁶. -4 mm / cycle, when ΔK is 26MPa·m 1 / 2 At this point, fatigue cracks enter a high-speed propagation stage.

[0059] Comparative Example 6

[0060] The original sample was a 7mm thick plate with an alloy composition of Al-4.2Cu-1.3Mg-0.9Mn (mass fraction %). First, it underwent solution treatment at 500℃ for 1 hour, followed by hot rolling at 470℃, with a final rolling temperature of 450℃ (10% hot rolling deformation). After hot rolling, it was water-quenched within 5 seconds. The resulting sample underwent low-temperature pre-aging treatment at 90℃ for 12 hours in a hot blast furnace. Then, the sample was immersed in a cryogenic medium for 10 minutes to lower its temperature to -170℃ for cryogenic asynchronous rolling at a rate ratio of 1.1 and a deformation of 20%. After cryogenic asynchronous rolling, the sample underwent final aging treatment at 100℃ for 6 hours in a hot blast furnace. The alloy treated in this example exhibited a tensile strength of 505.7 MPa, a yield strength of 443.1 MPa, and an elongation of 10.4%. The product obtained in this embodiment was tested for fatigue crack propagation rate under the conditions of 20℃ atmospheric environment, experimental loading waveform of sine wave, frequency of 10Hz, and stress ratio of 0.1; its fatigue crack propagation rate is: when ΔK is 10MPa·m 1 / 2 At that time, the fatigue crack propagation rate was 2.1 × 10⁻⁶. -4mm / cycle, when ΔK is 27MPa·m 1 / 2 At this point, fatigue cracks enter a high-speed propagation stage.

Claims

1. A heat treatment process for aluminum-copper-magnesium alloys, characterized in that: Includes the following steps: Step 1: Solution hot rolling continuous treatment The aluminum-copper-magnesium alloy is heated to the solution temperature in a resistance furnace and held at that temperature for a period of time. It is then rapidly transferred to a rolling mill for hot rolling, followed by cold water quenching. The solution temperature is between 480℃ and 500℃, and the holding time is between 30 and 90 minutes. The quenching transfer time should be ≤5 seconds. After solution treatment and holding, the alloy is cooled in the furnace or air-cooled to 455℃-475℃ before rolling begins, ensuring a final rolling temperature greater than 445℃. The hot rolling deformation is 5%-55%. Step 2: Low-temperature pre-aging treatment The alloy obtained in the first step is subjected to low-temperature pre-aging treatment in a hot air circulating furnace; the holding temperature of the low-temperature pre-aging treatment is 74℃-76℃, and the holding time is 7h-9h. Step 3: Cryogenic Asynchronous Rolling The alloy obtained in the second step is subjected to cryogenic asynchronous rolling at ultra-low temperatures, wherein the rolling temperature of cryogenic asynchronous rolling is -190℃ to -160℃, the speed ratio is 1.1-1.3, and the rolling deformation is 10%-20%. Step 4: Final Validity Processing The alloy obtained in the third step is subjected to final aging treatment in a hot air circulating furnace; the holding temperature for the fourth step of final aging is between 80℃ and 120℃, and the holding time is between 5h and 10h. The elemental composition and content of the aluminum-copper-magnesium alloy, expressed as a percentage by mass, include the following components: Cu 4.15-4.2%, Mg 1.25-1.35%, Mn 0.85-0.9%, balance Al; or Cu 4.15-4.2%, Mg 1.1-1.15%, Mn 0.68-0.72%, balance Al.

2. The heat treatment process for aluminum-copper-magnesium alloy according to claim 1, characterized in that: The solution treatment temperature is 490℃-500℃, the holding time is 60min-80min, and the quenching transfer time is 3-5s.

3. The heat treatment process for aluminum-copper-magnesium alloy according to claim 1, characterized in that: In the first step, the initial rolling temperature is 460℃-470℃, the final rolling temperature is 445℃-450℃, and the hot rolling deformation is 15%-35%.

4. The heat treatment process for aluminum-copper-magnesium alloy according to claim 1, characterized in that: The holding time for low-temperature pre-aging treatment is 7-7.5 hours.

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