A method for improving the fatigue properties of aluminum alloy 2014 forgings

Abstract

The application discloses a method for improving the fatigue performance of aluminum alloy 2014 forgings and relates to the technical field of aluminum alloy material preparation and processing. The technical scheme of the method is as follows: first, double-stage solid solution treatment is performed on the aluminum alloy 2014 forgings; then, the aluminum alloy 2014 forgings subjected to the double-stage solid solution treatment are subjected to room-temperature water quenching; subsequently, double-stage aging treatment is performed on the aluminum alloy 2014 forgings obtained after the room-temperature water quenching; finally, surface rolling treatment is performed on the aluminum alloy 2014 forgings subjected to the double-stage aging treatment. The fatigue performance of the aluminum alloy 2014 forgings prepared by the method is greatly improved, and the method can utilize the existing process equipment and is suitable for industrialized production.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy material preparation and processing technology, and more specifically, to a method for improving the fatigue properties of aluminum alloy 2014 forgings. Background Technology

[0002] The aviation industry is a crucial component of modern high-tech industries, representing a nation's advanced level of science and technology and industrial sophistication. With the increasing global demand for air transport, the production and use of large passenger and cargo aircraft have entered a phase of rapid development. In this process, aircraft weight, structural safety, and reliability have become core concerns for the aviation manufacturing industry. In particular, the landing gear system, as one of the key load-bearing components of an aircraft, directly affects the safety of takeoff, landing, and taxiing. The wheel hub is a vital component of the landing gear system, bearing the vertical and horizontal loads and impact forces during ground taxiing. Therefore, the strength, fatigue performance, and service life of the wheel hub are crucial to ensuring the overall safety of the aircraft.

[0003] As the size and weight of large aircraft continue to increase, wheel hubs need to withstand more complex alternating stresses and high-intensity workloads. Due to the frequent use of wheel hubs in flight, fatigue phenomena will occur during their service life, which may eventually lead to structural failure. This fatigue failure is mostly manifested as the initiation and propagation of fatigue cracks, and even the eventual fracture. Therefore, in-depth research on the fatigue behavior of wheel hubs under long-term service conditions is of great significance for improving aircraft safety. Currently, high-strength aluminum alloys are commonly used as the manufacturing material for aircraft wheel hubs. Among them, aluminum alloy 2014 is widely used in the manufacturing of wheel hubs for large aircraft due to its high specific strength, good fatigue resistance, and good heat resistance and corrosion resistance. Aluminum alloy 2014 belongs to the Al-Cu-Mg system and is heat-treatable. Its microstructure consists of α solid solution and phases such as θ' ​​(Al2Cu), S′ (Al2CuMg), Q (AlCuMgSi), and β′ (Mg2Si). Heat treatment can significantly improve its strength and heat resistance. However, its fatigue crack initiation and propagation behavior is also influenced by various factors such as material microstructure, residual stress, and surface roughness. Aircraft wheel hubs, under actual operating conditions, not only bear the combined effects of low-cycle fatigue and high-cycle fatigue but also face a complex alternating stress environment. Low-cycle fatigue typically occurs under high stress amplitude and few cycles, manifesting as large plastic deformation and localized stress concentration; while high-cycle fatigue occurs under lower stress amplitude and higher cycle count, usually resulting in material failure through slow crack propagation. Under such complex loading conditions, the laws governing crack initiation and propagation become more complex, and more influencing factors arise. Therefore, it is necessary to improve the comprehensive properties of aluminum alloy 2014 for aircraft wheel hubs, including tensile and fatigue properties. Currently, the main methods to improve the comprehensive performance of 2014 aluminum alloy are controlling the alloy composition and deformation heat treatment process. For example, the journal *Aluminum Processing* (Aluminum Processing, 2023 (04): 14-17) reported on "the influence of Cu, Mg, and Si element content on the microstructure and properties of 2014 aluminum alloy," indicating that increasing the content of Cu, Mg, and Si improves the alloy strength without reducing the elongation after fracture. The journal *Forging Technology* (Forging Technology, 2026, 51 (03): 247-253) reported on "the influence of artificial aging time on the microstructure of 2014 aluminum alloy forgings," suggesting that appropriate solution treatment and artificial aging processes should be selected to ensure a good microstructure in 2014 aluminum alloy forgings. However, none of these reports have studied the fatigue performance of 2014 aluminum alloy forgings.

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for improving the fatigue performance of aluminum alloy 2014 forgings. Summary of the Invention

[0005] The purpose of this invention is to provide a method for improving the fatigue properties of 2014 aluminum alloy forgings, employing a two-stage solution treatment, room temperature water quenching, a two-stage aging treatment, and surface rolling treatment. By optimizing the process conditions through the solution aging process and the surface rolling treatment, 2014 aluminum alloy forgings with high fatigue resistance are obtained.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a method for improving the fatigue properties of aluminum alloy 2014 forgings, the method comprising the following steps:

[0007] S1. Perform a two-stage solution treatment on aluminum alloy 2014 forgings;

[0008] S2. The aluminum alloy 2014 forgings that have undergone double solution treatment are subjected to room temperature water quenching;

[0009] S3. Perform a two-stage aging treatment on the aluminum alloy 2014 forgings obtained after room temperature water quenching;

[0010] S4. Perform surface rolling treatment on the aluminum alloy 2014 forgings that have undergone double-stage aging treatment.

[0011] The present invention is further configured such that: in the two-stage solution treatment, the first-stage solution temperature is 400~450 ℃, and the holding time is 1~5 h;

[0012] The second-stage solution treatment temperature is 510~530 ℃, and the holding time is 2~10 h.

[0013] The present invention is further configured such that: after solution treatment, the sample is quenched in room temperature water, the quenching transfer time does not exceed 50 s, and then it is transferred into an aging furnace.

[0014] The present invention is further configured such that: in the two-stage aging treatment, the first-stage aging temperature is 80~120 ℃ and the holding time is 1~5 h, and the second-stage aging temperature is 150~180 ℃ and the holding time is 5~10 h.

[0015] The present invention is further configured such that the surface rolling treatment is performed by ultrasonic rolling.

[0016] The present invention is further configured such that the specific process parameters for ultrasonic rolling forming are: ultrasonic static load of 0.1~0.25 MPa, spindle speed of 150~210 rpm, and feed rate of 0.05~0.15 mm / r.

[0017] In the method for improving the fatigue properties of aluminum alloy 2014 forgings of the present invention, the functions of each step are as follows:

[0018] 1. In the two-stage solution treatment, the first stage uses a lower temperature (400~450℃), which can preferentially dissolve the low melting point θ(Al2Cu) eutectic structure in aluminum alloy 2014 and allow the alloy to fully recover, reducing the internal stress and recrystallization driving force in the alloy. Thus, in the second stage solution treatment at a higher temperature (510~530℃), it can not only promote the full dissolution of sparingly soluble second phases such as S(Al2CuMg), but also effectively inhibit recrystallization and grain coarsening, avoiding the risk of high temperature overheating and significantly improving the solid solubility of the matrix.

[0019] 2. After solution treatment of aluminum alloy 2014, rapid cooling via room temperature water quenching freezes the high-temperature homogeneous solid solution, forming a supersaturated solid solution while retaining high-density vacancies. This provides solute reserves and nucleation conditions for the subsequent aging precipitation of GP zones and strengthening phases such as θ′(Al2Cu). At the same time, it effectively inhibits the continuous precipitation of coarse θ(Al2Cu) equilibrium phases at grain boundaries, avoiding a decrease in strength and corrosion resistance. The cooling rate needs to be faster than the critical value to ensure the strengthening effect, but it must be moderately controlled to prevent residual stress from causing deformation or cracking.

[0020] 3. Subsequently, a two-stage aging treatment is performed. The first stage (80~120 ℃) ​​promotes uniform nucleation in the GP region, providing dispersed nucleation sites for subsequent formation. The second stage (150~180 ℃) causes these nuclei to transform into fine and uniform nanoscale θ′ strengthening phases. Through the two-stage aging treatment, coarse grain boundary precipitates can be reduced, and the corrosion resistance and fracture toughness of the alloy can be significantly improved while maintaining high strength.

[0021] 4. Surface ultrasonic rolling treatment applies intense plastic deformation to the surface of the 2014 aluminum alloy forgings, causing strong plastic deformation in the surface material. This induces a large number of dislocations to multiply and move, forming a high dislocation density region. Simultaneously, the grains are significantly refined, generating a nanoscale grain structure, which effectively hinders dislocation movement and greatly improves hardness and strength. Furthermore, the residual compressive stress introduced into the surface layer can offset some of the tensile stress under the applied load, significantly slowing down the fatigue crack propagation rate and extending fatigue life. Compared to conventional mechanical surface treatments, this technology combines the advantages of both ultrasonic impact and rolling, producing impact and extrusion strengthening effects and achieving significant work hardening. Detailed Implementation

[0022] The present invention will now be described in further detail.

[0023] This invention uses 2014 aluminum alloy forgings as blanks and undergoes a combination of treatments including two-stage solution treatment, room temperature water quenching, two-stage aging, and surface rolling. Performance testing is conducted through room temperature tensile and fatigue tests. The fatigue test uses a tensile loading method with a stress ratio of 0.1, a sinusoidal load waveform, a cycle frequency of 30 Hz, and a maximum stress of 444 MPa.

[0024] Example 1

[0025] Aluminum alloy 2014 underwent a two-stage solution treatment: first, it was held at 400℃ for 1 hour, then at 510℃ for 5 hours. After solution treatment, it was quenched in room temperature water with a quenching transfer time of 50 seconds, and then transferred to an aging furnace. After solution quenching, it was held at 80℃ for 5 hours, and then at 150℃ for 10 hours. After solution aging, the surface underwent ultrasonic rolling treatment with an ultrasonic static load of 0.15 MPa, a spindle speed of 150 rpm, and a feed rate of 0.1 mm / r. Room temperature tensile and fatigue properties were tested, and the results are shown in Table 1.

[0026] Example 2

[0027] Aluminum alloy 2014 underwent a two-stage solution treatment: first, it was held at 450℃ for 5 hours, then at 530℃ for 2 hours. After solution treatment, it was quenched in room temperature water with a quenching transfer time of 30 seconds, and then transferred to an aging furnace. After solution quenching, it was held at 120℃ for 1 hour, and then at 180℃ for 5 hours. After solution aging, the surface underwent ultrasonic rolling treatment with an ultrasonic static load of 0.2 MPa, a spindle speed of 150 rpm, and a feed rate of 0.1 mm / r. Room temperature tensile and fatigue properties were tested, and the results are shown in Table 1.

[0028] Example 3

[0029] Aluminum alloy 2014 underwent a two-stage solution treatment: first, it was held at 430℃ for 3 hours, then at 520℃ for 8 hours. After solution treatment, it was quenched in room temperature water with a quenching transfer time of 50 seconds, and then transferred to an aging furnace. After solution quenching, it was held at 100℃ for 3 hours, and then at 160℃ for 7 hours. After solution aging, the surface underwent ultrasonic rolling treatment with an ultrasonic static load of 0.25 MPa, a spindle speed of 150 rpm, and a feed rate of 0.1 mm / r. Room temperature tensile and fatigue properties were tested, and the results are shown in Table 1.

[0030] Example 4

[0031] Aluminum alloy 2014 underwent a two-stage solution treatment: first, it was held at 420℃ for 5 hours, then at 530℃ for 3 hours. After solution treatment, it was quenched in room temperature water with a quenching transfer time of 30 seconds, and then transferred to an aging furnace. After solution quenching, it was held at 100℃ for 5 hours, and then at 180℃ for 5 hours. After solution aging, the surface underwent ultrasonic rolling treatment with an ultrasonic static load of 0.15 MPa, a spindle speed of 150 rpm, and a feed rate of 0.1 mm / r. Room temperature tensile and fatigue properties were tested, and the results are shown in Table 1.

[0032] Example 5

[0033] Aluminum alloy 2014 underwent a two-stage solution treatment: first, it was held at 420℃ for 5 hours, then at 530℃ for 3 hours. After solution treatment, it was quenched in room temperature water with a quenching transfer time of 30 seconds, and then transferred to an aging furnace. After solution quenching, it was held at 100℃ for 5 hours, and then at 180℃ for 5 hours. After solution aging, the surface underwent ultrasonic rolling treatment with an ultrasonic static load of 0.15 MPa, a spindle speed of 100 rpm, and a feed rate of 0.1 mm / r. Room temperature tensile and fatigue properties were tested, and the results are shown in Table 1.

[0034] Example 6

[0035] Aluminum alloy 2014 underwent a two-stage solution treatment: first, it was held at 450℃ for 1 hour, then at 510℃ for 2 hours. After solution treatment, it was quenched in room temperature water with a quenching transfer time of 50 seconds, and then transferred to an aging furnace. After solution quenching, it was held at 100℃ for 5 hours, and then at 180℃ for 5 hours. After solution aging, the surface underwent ultrasonic rolling treatment with an ultrasonic static load of 0.15 MPa, a spindle speed of 100 rpm, and a feed rate of 0.1 mm / r. Room temperature tensile and fatigue properties were tested, and the results are shown in Table 1.

[0036] Comparative Example 1

[0037] Aluminum alloy 2014 was held at 510 ℃ for 5 h, then quenched in room temperature water for 60 s after solution treatment. It was then transferred to an aging furnace and held at 150 ℃ for 10 h. After cooling to room temperature, room temperature tensile and fatigue properties were tested, and the properties are shown in Table 1.

[0038] Comparative Example 2

[0039] Aluminum alloy 2014 was held at 530 ℃ for 2 h, then quenched in room temperature water for 70 s after solution treatment. It was then transferred to an aging furnace and held at 180 ℃ for 6 h. After cooling to room temperature, room temperature tensile and fatigue properties were tested, and the properties are shown in Table 1.

[0040] Comparative Example 3

[0041] Aluminum alloy 2014 was held at 530 ℃ for 2 h, then solution-treated and quenched in room temperature water for 51 s. It was then transferred to an aging furnace and held at 180 ℃ for 6 h, followed by cooling to room temperature. After aging, the surface underwent ultrasonic rolling treatment with a static load of 0.1 MPa, a spindle speed of 150 rpm, and a feed rate of 0.1 mm / r. Room temperature tensile and fatigue properties were then tested, and the results are shown in Table 1.

[0042] Table 1. Room temperature properties of the alloys of the present invention

[0043]

[0044] Comparing the performance parameter values ​​of the examples and the comparative examples, it can be seen that the tensile strength, yield strength and elongation of the aluminum alloy 2014 forgings after the composite treatment of double-stage solution treatment, room temperature water quenching, double-stage aging treatment and forging surface rolling treatment are not significantly reduced, but the fatigue performance is significantly higher than that of the alloy in the comparative examples.

[0045] Working Principle: This invention employs a combination of two-stage solution treatment, room temperature water quenching, two-stage aging treatment, and surface ultrasonic rolling forming. In the two-stage solution treatment, the first stage uses a lower temperature (400~450℃) to preferentially dissolve the low-melting-point θ(Al2Cu) eutectic structure in aluminum alloy 2014, allowing the alloy to fully recover and reducing internal stress and recrystallization driving force. This, in the second stage at a higher temperature (510~530℃), not only promotes the full dissolution of sparingly soluble second phases such as S(Al2CuMg), but also effectively inhibits recrystallization and grain coarsening, avoiding the risk of overheating and significantly improving the solubility of the matrix. After solution treatment of aluminum alloy 2014, rapid cooling freezes the high-temperature homogeneous solid solution, forming a supersaturated solid solution and retaining high-density vacancies. This provides solute reserves and nucleation conditions for the subsequent aging precipitation of GP zones and strengthening phases such as θ′(Al2Cu). At the same time, it effectively inhibits the continuous precipitation of coarse θ(Al2Cu) equilibrium phases at grain boundaries, avoiding a decrease in strength and corrosion resistance. The cooling rate needs to be faster than the critical value to ensure the strengthening effect, but it must be moderately controlled to prevent residual stress from causing deformation or cracking.

[0046] After solution quenching, aluminum alloy 2014 undergoes a staged treatment combining low-temperature pre-precipitation and high-temperature main precipitation. The first stage (80~120 ℃) ​​promotes uniform nucleation in the GP zone, providing dispersed nucleation sites for subsequent processes. The second stage (150~180 ℃) transforms these nuclei into fine, uniform nanoscale θ′ strengthening phases. Through this two-stage aging treatment, coarse grain boundary precipitates are reduced, significantly improving the alloy's corrosion resistance and fracture toughness while maintaining high strength.

[0047] Surface ultrasonic rolling treatment applies intense plastic deformation to the surface of 2014 aluminum alloy forgings, causing strong plastic deformation in the surface material. This induces a large number of dislocations to multiply and move, forming a high dislocation density region. Simultaneously, the grains are significantly refined, generating a nanoscale grain structure that effectively hinders dislocation movement, greatly improving hardness and strength. Furthermore, the residual compressive stress introduced into the surface layer can offset some of the tensile stress under external load, significantly slowing down the fatigue crack propagation rate and extending fatigue life. Compared to conventional mechanical surface treatments, this technology combines the advantages of both ultrasonic impact and rolling, producing impact and extrusion strengthening effects and achieving significant work hardening.

[0048] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for improving the fatigue properties of aluminum alloy 2014 forgings, characterized in that: The method includes the following steps: S1. Perform a two-stage solution treatment on aluminum alloy 2014 forgings; S2. The aluminum alloy 2014 forgings that have undergone double solution treatment are subjected to room temperature water quenching; S3. Perform a two-stage aging treatment on the aluminum alloy 2014 forgings obtained after room temperature water quenching; S4. Perform surface rolling treatment on the aluminum alloy 2014 forgings that have undergone double-stage aging treatment.

2. The method for improving the fatigue properties of aluminum alloy 2014 forgings according to claim 1, characterized in that: In the two-stage solution treatment, the first-stage solution temperature is 400~450 ℃, and the holding time is 1~5 h. The second-stage solution treatment temperature is 510~530 ℃, and the holding time is 2~10 h.

3. The method for improving the fatigue properties of aluminum alloy 2014 forgings according to claim 2, characterized in that: The steps of room temperature water quenching are as follows: after solution treatment, quench in room temperature water, the quenching transfer time does not exceed 50 s, and then transfer to an aging furnace.

4. The method for improving the fatigue properties of aluminum alloy 2014 forgings according to claim 3, characterized in that: In the two-stage aging treatment, the first-stage aging temperature is 80~120 ℃ and the holding time is 1~5 h, and the second-stage aging temperature is 150~180 ℃ and the holding time is 5~10 h.

5. The method for improving the fatigue properties of aluminum alloy 2014 forgings according to claim 4, characterized in that: The surface rolling treatment is performed using ultrasonic rolling.

6. The method for improving the fatigue properties of aluminum alloy 2014 forgings according to claim 5, characterized in that: The specific process parameters for ultrasonic roll forming are as follows: ultrasonic static load 0.1~0.25 MPa, spindle speed 150~210 rpm, and feed rate 0.05~0.15 mm / r.

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