Preparation method of metal liner for prolonging fatigue life of composite material container

Abstract

The invention relates to the technical field of high-pressure gas storage containers, and discloses a preparation method of a metal inner container capable of prolonging the fatigue life of a composite container, and the preparation method comprises the following steps: obtaining an alloy material for preparing the metal inner container; wherein the alloy material comprises one of aluminum alloy, stainless steel or titanium alloy; and the alloy material is treated through matched accumulative true plastic deformation, isothermal aging and surface strengthening, and the metal inner container is obtained. Wherein when the alloy material is the aluminum alloy or the stainless steel, the 0.2% yield strain of the metal liner is not less than 0.60%; and when the alloy material is the titanium alloy, the 0.2% yield strain of the metal liner is not less than 2.50%, and the elastic modulus is 45-55 GPa. According to the technical scheme, the cycle life and the structural reliability of the composite material container under the high-frequency charging and discharging load working condition can be prolonged.

Description

Technical Field

[0001] This application relates to the field of high-pressure gas storage container technology, and in particular to a method for preparing a metal liner to improve the fatigue life of a composite material container. Background Technology

[0002] The significant mismatch between the metal liner and the CFRP winding layer in composite containers at 0.2% yield strain capacity leads to easy yielding, plastic deformation, and fatigue damage of the liner during high-frequency inflation and deflation cycles. Existing solutions, such as geometric compensation design, material microalloying, and heat treatment, can partially alleviate yielding and improve the strength of the metal liner, but their effect on improving the 0.2% yield strain is limited, and the synergistic effect between the two has not been fully resolved.

[0003] Therefore, how to effectively solve the elastic mismatch between the metal liner and the CFRP winding layer of composite material containers, which leads to liner yielding, residual plastic deformation and fatigue damage during the filling and discharging cycle of gas cylinders, is a technical problem that urgently needs to be solved. Summary of the Invention

[0004] This application provides a method for preparing a metal liner to improve the fatigue life of a composite material container. It achieves the technical effect of realizing the elastic coordination between the metal liner and the CFRP winding layer of the composite material container, effectively suppressing stress-induced plasticity and ratchet damage, thereby improving the cycle life and structural reliability of the composite material container under high-frequency charging and discharging load conditions.

[0005] To achieve the above objectives, the main technical solutions adopted in this application include: In a first aspect, embodiments of this application provide a method for preparing a metal liner to improve the fatigue life of a composite material container, the preparation method comprising: An alloy material for preparing a metal liner is obtained; wherein the alloy material includes one of aluminum alloy, stainless steel, or titanium alloy; the alloy material is subjected to matched cumulative true plastic deformation, isothermal aging, and surface strengthening treatments to obtain the metal liner; wherein... When the alloy material is the aluminum alloy or the stainless steel, the 0.2% yield strain of the metal liner is not less than 0.60%; when the alloy material is the titanium alloy, the 0.2% yield strain of the metal liner is not less than 2.50%, and the elastic modulus is 45-55 GPa.

[0006] This embodiment provides a method for preparing a metal liner to improve the fatigue life of a composite material container. The metal liner has a yield strain of 0.2% (ε). 0.2The yield strength is significantly increased to 0.65%–2.9%, far exceeding the 0.2%–0.3% of traditional liner materials. This improvement helps to achieve consistent deformation between the metal liner and the carbon fiber reinforced polymer (CFRP) winding layer within the designed elastic range, effectively suppressing the ratchet effect, delaying yield propagation, and improving the stability and service life of the structure.

[0007] In one embodiment, the aluminum alloy comprises, by mass fraction: Mg: 4.3-4.8%, Mn: 0.4-0.7%, Cr: 0.05-0.25%, Fe and Si total not exceeding 0.20%, with the balance being Al and unavoidable impurities, and simultaneously satisfying: a single impurity not exceeding 0.05%, and the total amount of impurities not exceeding 0.15%.

[0008] This embodiment optimizes the composition of the aluminum alloy, particularly adjusting the content of elements such as Mg, Mn, and Cr, and strictly controls the level of impurities. This aluminum alloy effectively solves the elastic mismatch problem between the metal inner liner and the CFRP winding layer. During the inflation and deflation cycle, this alloy material prevents the inner liner from yielding and undergoing residual plastic deformation, thereby reducing fatigue damage and significantly improving the reliability and service life of the composite material container.

[0009] In one embodiment, the aluminum alloy is annealed before the cumulative true plastic deformation treatment; wherein the annealing conditions are: holding at a temperature of 455-465°C for 12 hours.

[0010] In this embodiment, the aluminum alloy is annealed before the cumulative true plastic deformation treatment, especially under the condition of holding at 455-465℃ for 12 hours, which can significantly improve the microstructure of the aluminum alloy. Annealing treatment improves the plasticity and toughness of the aluminum alloy by eliminating internal stress and microstructural inhomogeneity, eliminating embrittled phases (such as β-Mg5Al8 phase). The annealed aluminum alloy exhibits stronger yield strength and fatigue resistance under cyclic loading, which is crucial for the metal liner of composite container.

[0011] In one embodiment, when the alloy material is an aluminum alloy, the cumulative true plastic deformation matching the aluminum alloy includes: The aluminum alloy is extruded 4 to 8 times at room temperature through a channel angle of 110° to obtain the extruded aluminum alloy. The extruded aluminum alloy is subjected to cryogenic rolling at a temperature of -196°C with a thickness reduction of 60-75%, to obtain an aluminum alloy after cumulative true plastic deformation. Accordingly, the isothermal aging of the aluminum alloy includes: holding the aluminum alloy after cumulative true plastic deformation at a temperature of 295-305°C for 0.8-1.2 hours to obtain the isothermal aged aluminum alloy; Accordingly, the surface strengthening of the aluminum alloy includes: shot peening the isothermally aged aluminum alloy with an intensity of 0.4 to 0.6 mmA to form a ZrO2 ceramic coating with a thickness of 0.20 to 0.30 mm on the surface, thereby obtaining the metal liner.

[0012] This embodiment significantly improves the mechanical properties of aluminum alloys through a series of processes including equal-channel angular extrusion, cryogenic rolling, isothermal aging, and surface strengthening. First, equal-channel angular extrusion refines the grain size of the aluminum alloy, improving its strength and toughness. Subsequently, cryogenic rolling further optimizes the microstructure of the aluminum alloy, enhancing its fatigue resistance. Isothermal aging under controlled temperature conditions increases the hardness and strength of the aluminum alloy, enhancing its long-term stability. Finally, shot peening and coating with a ZrO2 ceramic coating enhance the wear resistance and corrosion resistance of the aluminum alloy surface. These processes not only effectively solve the elastic mismatch problem between the metal liner and the CFRP winding layer in composite material containers but also improve the container's resistance to yielding, plastic deformation, and fatigue damage, thereby significantly improving the reliability and durability of the composite material container.

[0013] In one embodiment, the stainless steel comprises, by mass fraction: C not more than 0.03%, Cr: 16.0-18.0%, Ni: 10.0-14.0%, Mo: 2.0-3.0%, N: 0.015-0.030%, B: 0.002-0.004%, with the balance being Fe and unavoidable impurities.

[0014] This embodiment improves the corrosion resistance of the material by increasing the chromium and molybdenum content, reducing the risk of container failure. The addition of nickel enhances the strength and toughness of the metal, making it less prone to yielding or residual plastic deformation under pressure and impact. The addition of boron and nitrogen helps refine the grain size, improving the material's fatigue resistance and fracture resistance. Using this stainless steel as the metal liner material not only improves the container's strength, corrosion resistance, and fatigue performance, but also effectively solves the elastic mismatch problem between the metal liner and the CFRP winding layer, significantly improving the long-term stability and reliability of the composite material container.

[0015] In one embodiment, when the alloy material is stainless steel, the cumulative true plastic deformation matching the stainless steel includes: For the stainless steel bottle body, a cold stretching of 60-75% of the total deformation is applied along the axial direction of the bottle body to obtain stainless steel after cumulative true plastic deformation. Accordingly, the isothermal aging of the stainless steel includes: holding the stainless steel after cumulative true plastic deformation at a temperature of 340-360°C for 0.3-0.7 hours to obtain isothermal aged stainless steel; Accordingly, the surface strengthening of the stainless steel includes: using laser shock blasting to form a nanocrystalline layer with a thickness of 0.10–0.20 mm on the surface of the isothermally aged stainless steel to obtain the metal liner; wherein the energy density of the laser shock blasting is 8–12 J / cm². 2 The pulse width is 15–25 ns, and the number of pulses is 2–4.

[0016] In this embodiment, cold stretching, by applying 60-75% of the total deformation, enhances the strength and plasticity of the stainless steel, improves fatigue resistance and yield strain to 0.2%, effectively preventing yielding and residual plastic deformation of the metal liner during filling and discharging cycles. Isothermal aging further enhances the strength and toughness of the stainless steel, prevents grain growth, and ensures the stability of the material during cylinder use. The nanocrystalline layer formed by laser shock surface strengthening not only improves surface strength and fatigue resistance but also increases resistance to crack propagation, significantly extending the fatigue life of the metal liner. Ultimately, through the combination of these precise processes, the metal liner in the composite cylinder with the CFRP winding layer possesses higher strength, fatigue resistance, and toughness, effectively withstanding the high-pressure environment of filling and discharging cycles, ensuring the safety and service life of the cylinder.

[0017] In one embodiment, the titanium alloy comprises, by mass fraction: Nb: 20.0–26.0%, Zr: 2.5–5.0%, Sn: 6.0–9.5%, O: 0.25–0.45%, with the balance being Ti and unavoidable impurities.

[0018] This embodiment enhances the strength, toughness, and fatigue resistance of the titanium alloy by incorporating elements such as Nb, Zr, Sn, and O. The strengthening effect of Nb and Zr, in particular, improves the yield strength and tensile strength of the titanium alloy, while also enhancing its high-temperature performance. This allows the metal liner to withstand significant mechanical stress during inflation and deflation and effectively accommodates the elastic differences between itself and the CFRP winding layer. Furthermore, the high strength and good plasticity of the titanium alloy make the liner more stable during inflation and deflation cycles, reducing deformation and damage caused by elastic mismatch. Ultimately, the application of this titanium alloy material significantly improves the strength, fatigue resistance, and safety of the gas cylinder, extends its service life, and ensures the stability of the gas cylinder under complex operating conditions.

[0019] In one embodiment, the titanium alloy is subjected to homogenization heat treatment before the cumulative true plastic deformation treatment; wherein the conditions for the homogenization heat treatment are: holding at a temperature of 1000-1020°C for 2-3 hours.

[0020] In this embodiment, the titanium alloy undergoes homogenization heat treatment before cumulative true plastic deformation to eliminate microstructural segregation that may occur during casting, such as compositional inhomogeneity and inconsistent grain size. These segregations affect material properties. Holding at a high temperature of 1000–1020°C for 2–3 hours promotes the diffusion of alloying elements, further homogenizing the material's microstructure. Under high-temperature conditions, the diffusion rate of alloying elements accelerates, effectively eliminating compositional segregation and forming a uniform solid solution. A uniform microstructure is crucial for subsequent plastic deformation, improving the material's plasticity and toughness. Prolonged holding not only ensures uniform internal temperature but also allows for sufficient diffusion and uniform distribution of alloying elements, providing a better foundation for subsequent true plastic deformation and enhancing the overall performance of the titanium alloy.

[0021] In one embodiment, when the alloy material is a titanium alloy, the cumulative true plastic deformation matching the titanium alloy includes: The titanium alloy is cold-rolled to reduce its thickness by 85-92% to obtain a titanium alloy after cumulative true plastic deformation. Accordingly, the isothermal aging of the titanium alloy includes: holding the titanium alloy after cumulative true plastic deformation at a temperature of 440-460°C for 0.8-1.2 hours to obtain the isothermal aged titanium alloy; Accordingly, the surface strengthening of the titanium alloy includes: using laser shock or shot peening to introduce a residual compressive stress layer of -300 to -500 MPa on the surface of the isothermally aged titanium alloy to obtain the metal liner.

[0022] In this embodiment, cold rolling deformation, with a thickness reduction of 85-92%, refines the grains and introduces dislocation structures, enhancing the fatigue resistance and crack propagation resistance of the titanium alloy, and reducing the yielding and plastic deformation of the metal liner during gas filling and discharging cycles. Subsequently, isothermal aging treatment promotes the precipitation of the ω phase, increasing the yield strain of the titanium alloy by 0.2%, enhancing the liner's resistance to external stress, and further alleviating the elastic mismatch between the metal liner and the CFRP winding layer. Finally, a residual compressive stress layer is introduced on the liner surface using laser shock peening or shot peening technology, significantly improving its fatigue resistance and crack propagation resistance, effectively preventing crack initiation and propagation. Combining these processes, the durability and safety of the titanium alloy liner during gas filling and discharging cycles are significantly improved, thereby effectively enhancing the overall performance and service life of the composite material container.

[0023] Secondly, embodiments of this application provide a metal liner for improving the fatigue life of composite material containers, which is prepared using the aforementioned method for preparing a metal liner for improving the fatigue life of composite material containers.

[0024] Thirdly, embodiments of this application provide a composite material container, wherein the composite material container is obtained by preparing a metal liner by the preparation method described above, or by winding the metal liner and carbon fiber reinforced composite material described above. Attached Figure Description

[0025] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 An optical micrograph of the annealed aluminum alloy provided in Embodiment 1 of this application; Figure 2 Transmission electron microscopy image of aluminum alloy after cumulative true plastic deformation, provided in Example 1 of this application. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0027] Composite material containers are a typical type of high-performance gas storage container, widely used in high-pressure gas storage and other fields. Their core components include a metal inner liner and an outer carbon fiber reinforced polymer (CFRP) winding layer. The metal inner liner provides airtightness and structural support, while the CFRP winding layer primarily bears the circumferential and axial stresses of the gas cylinder, significantly improving the container's load-bearing capacity and strength, thus achieving the design goal of both lightweight and high strength. Composite material containers typically operate at pressures in the range of 35–70 MPa, exhibiting high gas storage capacity and structural stability.

[0028] However, in practical applications, there are certain differences in material properties between the metal liner and the CFRP winding layer of composite material containers, especially in terms of strain capacity. The metal liner is often made of 6061-T6 aluminum alloy, which has high strength and a low yield strain of 0.2% (ε). 0.2The yield strain is typically less than 0.20%, far lower than the typical 0.2% yield strain (0.60–0.80%) of CFRP windings. This performance difference makes the metal liner prone to yielding first in the inner liner during the gas cylinder filling and discharging cycle, causing plastic deformation and residual strain, further leading to ratcheting effect and local yield propagation, thus affecting the long-term service life of the gas cylinder. It should be noted that 0.2% yield strain refers to the stress value corresponding to the material strain reaching 0.2%. This stress value indicates that the material begins to exhibit slight plastic deformation at the 0.2% strain level, which is a characteristic point of the material transitioning from elastic deformation to plastic deformation.

[0029] Due to the significant strain capacity mismatch between the metal liner and the CFRP winding layer during the elastic phase, gas cylinders are prone to fatigue damage during high-frequency filling and discharging cycles. To mitigate this problem, existing technologies have proposed several solutions, such as geometric compensation design, material micro-alloying, and heat treatment adjustments.

[0030] Geometric compensation design: Some solutions use corrugated or variable wall thickness structures to locally delay the yielding of the metal liner. However, while these structures can alleviate yielding to some extent, the complex manufacturing process and the tendency to generate stress concentration at the interface can lead to excessive stress in local areas, thereby accelerating material fatigue damage.

[0031] Microalloying and heat treatment: Improving the strength of a metal liner by adding trace amounts of alloying elements or through heat treatment has become a common technical approach. However, while these methods can improve the strength and yield strength of the metal liner, their effect on increasing the yield strain by 0.2% is limited, and they cannot completely solve the problem of elastic mismatch.

[0032] Heat treatment optimization: The material properties of the metal liner can be improved to a certain extent during the heat treatment process. However, since the 0.2% yield strain of the CFRP winding layer is much higher than that of the metal liner, it is still a great challenge to rely solely on heat treatment to improve the synergistic effect between the two.

[0033] Therefore, how to effectively solve the elastic mismatch between the metal liner and the CFRP winding layer of composite material containers, which leads to liner yielding, residual plastic deformation and fatigue damage during the filling and discharging cycle of gas cylinders, is a technical problem that urgently needs to be solved.

[0034] To address the aforementioned technical problems, according to an embodiment of this application, a method for preparing a metal liner to improve the fatigue life of a composite material container is provided. The method includes: obtaining an alloy material for preparing the metal liner; wherein the alloy material includes one of aluminum alloy, stainless steel, or titanium alloy; subjecting the alloy material to matching cumulative true plastic deformation, isothermal aging, and surface strengthening treatments to obtain the metal liner; wherein, when the alloy material is aluminum alloy or stainless steel, the 0.2% yield strain of the metal liner is not less than 0.60%; when the alloy material is titanium alloy, the 0.2% yield strain of the metal liner is not less than 2.50%, and the elastic modulus is 45–55 GPa.

[0035] Specifically, when the material is an aluminum alloy, 60%–75% cumulative true plastic deformation is introduced through equal channel angular extrusion (ECAP). After holding at 300℃±5℃ for 1 hour, a dispersed β-Mg5Al8 phase precipitates. The surface is then shot-peened (Almen strength 0.5 mmA) and a 0.25 mm ZrO2 ceramic coating is deposited. The yield strain is 0.2% (ε... 0.2 The tensile strength is increased to 0.65%–0.70%, reaching 320–340 MPa. When the material is stainless steel, 60–75% cold stretching deformation is applied along the axial direction of the bottle. Holding at 350℃±10℃ for 0.5 hours induces the precipitation of Cr2N nanophase. Laser shock treatment (energy density 10 J / cm³) is then performed. 2 (Pulse width 20 ns, repeated 3 times) to form a 0.10–0.20 mm thick nanocrystalline layer. 0.2% yield strain (ε 0.2 The yield strength is approximately 0.75%, and the tensile strength is not less than 650 MPa. When the material is a titanium alloy, cold rolling deformation results in a thickness reduction of 85-92%. Holding at 440-460℃ for 0.8-1.2 hours precipitates a dispersed ω-phase with a particle size of 5-15 nm. Laser shock peening or shot peening introduces a residual compressive stress layer of -300 to -500 MPa. The yield strain is 0.2% (ε). 0.2 The α value is 2.8–3.1%, and the elastic modulus is 45–55 GPa.

[0036] This embodiment provides a method for preparing a metal liner to improve the fatigue life of a composite material container. The metal liner has a yield strain of 0.2% (ε). 0.2 The yield strength is significantly increased to 0.65%–2.9%, far exceeding the 0.2%–0.3% of traditional liner materials. This improvement helps to achieve consistent deformation between the metal liner and the carbon fiber reinforced polymer (CFRP) winding layer within the designed elastic range, effectively suppressing the ratchet effect, delaying yield propagation, and improving the stability and service life of the structure.

[0037] In one embodiment, the aluminum alloy comprises, by mass fraction: Mg: 4.3-4.8%, Mn: 0.4-0.7%, Cr: 0.05-0.25%, Fe and Si total not exceeding 0.20%, with the balance being Al and unavoidable impurities, and simultaneously satisfying: a single impurity not exceeding 0.05%, and the total amount of impurities not exceeding 0.15%.

[0038] Specifically, magnesium is the main strengthening element in aluminum alloys, enhancing their strength and corrosion resistance. A magnesium content of 4.3% to 4.8% is considered medium to high, suitable for applications requiring high strength and low density (such as gas cylinders). Manganese is commonly used as an alloying element to improve the strength of aluminum alloys, while also enhancing corrosion resistance. A manganese content of 0.4% to 0.7% helps reduce internal stress and improve plasticity in aluminum alloys. Chromium contributes to improved corrosion and oxidation resistance, but its content is kept low (0.05% to 0.25%) to avoid affecting the alloy's machinability. Since Fe and Si elements can cause brittleness and casting defects in aluminum alloys, their total content must be controlled to less than 0.20%. By controlling the content of a single impurity to no more than 0.05% and the total impurities to no more than 0.15%, high alloy purity can be ensured, thereby improving machinability and the quality of the final metal liner.

[0039] This embodiment optimizes the composition of the aluminum alloy, particularly adjusting the content of elements such as Mg, Mn, and Cr, and strictly controls the level of impurities. This aluminum alloy effectively solves the elastic mismatch problem between the metal inner liner and the CFRP winding layer. During the inflation and deflation cycle, this alloy material prevents the inner liner from yielding and undergoing residual plastic deformation, thereby reducing fatigue damage and significantly improving the reliability and service life of the composite material container.

[0040] In one embodiment, the aluminum alloy is annealed before the cumulative true plastic deformation treatment; wherein the annealing conditions are: holding at a temperature of 455-465°C for 12 hours.

[0041] Specifically, alloying elements in aluminum alloys, such as magnesium, manganese, and chromium, have high solubility in the aluminum matrix. Through annealing, these alloying elements can fully dissolve in the aluminum matrix, forming a uniform solid solution structure. This structure helps improve the strength and ductility of the aluminum alloy, especially during subsequent processing. Annealing involves heating the metal to a certain temperature and holding it for a certain time, causing changes in the material's microstructure, thereby softening, relieving internal stress, and improving ductility.

[0042] In the manufacture of composite material containers, the metal liner needs to withstand the storage requirements of high-pressure gases, especially during the frequent filling and emptying cycles of gas cylinders, where the material properties of the metal liner are crucial. Aluminum alloys can fully dissolve alloying elements and diffuse them into the aluminum matrix within a temperature range of 455℃ to 465℃. This temperature range effectively eliminates the β-Mg5Al8 phase in aluminum alloys; if this phase is not eliminated, it can lead to embrittlement of the metal, thereby reducing the mechanical properties of the alloy.

[0043] The 12-hour holding time during annealing ensures the homogenization of the aluminum alloy, resulting in more stable performance. Especially under cyclic loading, the annealed aluminum alloy exhibits better yield strength and fatigue resistance. Annealing also eliminates potential stress concentration points and microstructural inhomogeneities in the aluminum alloy, thereby improving the long-term service life of the metal liner of the composite container. Through high-temperature annealing, the metal liner can better withstand the effects of long-term high-frequency inflation and deflation, reducing yielding, plastic deformation, and localized fatigue damage.

[0044] In this embodiment, the aluminum alloy is annealed before the cumulative true plastic deformation treatment, especially under the condition of holding at 455-465℃ for 12 hours, which can significantly improve the microstructure of the aluminum alloy. Annealing treatment improves the plasticity and toughness of the aluminum alloy by eliminating internal stress and microstructural inhomogeneity, eliminating embrittled phases (such as β-Mg5Al8 phase). The annealed aluminum alloy exhibits stronger yield strength and fatigue resistance under cyclic loading, which is crucial for the metal liner of composite container.

[0045] In one embodiment, when the alloy material is an aluminum alloy, the cumulative true plastic deformation matching the aluminum alloy includes: extruding the aluminum alloy at room temperature through equal channel angles of 110° for 4 to 8 passes to obtain the extruded aluminum alloy; and performing deep cryogenic rolling on the extruded aluminum alloy at a temperature of -196° with a thickness reduction of 60 to 75% to obtain the aluminum alloy after cumulative true plastic deformation.

[0046] Specifically, at room temperature, aluminum alloys undergo intense shear deformation through 4–8 passes of 110° equal-channel extrusion. This deformation triggers rapid dislocation proliferation, leading to grain refinement to the submicron scale. Grain refinement significantly improves the strength and toughness of the aluminum alloy. Shear deformation introduces numerous dislocations and subgrain boundaries into the aluminum alloy; these defects hinder dislocation movement, thereby increasing the alloy's strength. Subsequent cryogenic rolling at an extremely low temperature of -196°C, with a thickness reduction of 60–75%, further compacts the subgrain structure of the aluminum alloy, reducing defects at grain boundaries and subgrain boundaries, and further improving the alloy's strength, hardness, and fatigue resistance. Deformation under low-temperature conditions also increases the distortion region of the aluminum alloy, effectively improving its resistance to deformation.

[0047] Accordingly, the isothermal aging of the aluminum alloy includes: holding the aluminum alloy after cumulative true plastic deformation at a temperature of 295-305℃ for 0.8-1.2h to obtain the isothermal aged aluminum alloy.

[0048] Specifically, under intermediate temperature conditions, alloying elements (such as magnesium) in aluminum alloys precipitate to form dispersed phases (such as β-Mg5Al8). These dispersed phases are distributed around grain boundaries and dislocations, effectively locking the subgrain structure. The precipitation of dispersed phases can significantly improve the yield strength and elastic modulus of the material, thereby increasing the yield-elasticity ratio.

[0049] Accordingly, the surface strengthening of the aluminum alloy includes: shot peening the isothermally aged aluminum alloy with an intensity of 0.4 to 0.6 mmA to form a ZrO2 ceramic coating with a thickness of 0.20 to 0.30 mm on the surface, thus obtaining a metal liner.

[0050] Specifically, shot peening introduces residual compressive stress exceeding -300 MPa onto the material surface, improving its fatigue resistance. Depositing a ZrO2 ceramic coating on the surface further enhances its wear resistance and fatigue resistance. This results in an average grain size controlled below 13 μm, significantly refining the grains and improving the strength and toughness of the metal liner.

[0051] This embodiment significantly improves the mechanical properties of aluminum alloys through a series of processes including equal-channel angular extrusion, cryogenic rolling, isothermal aging, and surface strengthening. First, equal-channel angular extrusion refines the grain size of the aluminum alloy, improving its strength and toughness. Subsequently, cryogenic rolling further optimizes the microstructure of the aluminum alloy, enhancing its fatigue resistance. Isothermal aging under controlled temperature conditions increases the hardness and strength of the aluminum alloy, enhancing its long-term stability. Finally, shot peening and coating with a ZrO2 ceramic coating enhance the wear resistance and corrosion resistance of the aluminum alloy surface. These processes not only effectively solve the elastic mismatch problem between the metal liner and the CFRP winding layer in composite material containers but also improve the container's resistance to yielding, plastic deformation, and fatigue damage, thereby significantly improving the reliability and durability of the composite material container.

[0052] In one embodiment, the stainless steel comprises, by mass fraction: C not more than 0.03%, Cr: 16.0 to 18.0%, Ni: 10.0 to 14.0%, Mo: 2.0 to 3.0%, N: 0.015 to 0.030%, B: 0.002 to 0.004%, with the balance being Fe and unavoidable impurities.

[0053] Specifically, a low carbon content can prevent the precipitation of carbides during welding and heat treatment, thereby reducing the risk of intergranular corrosion. A chromium content in the range of 16.0%–18.0% ensures good corrosion resistance while avoiding excessive chromium content that could reduce toughness and plasticity. A nickel content in the range of 10.0%–14.0% ensures the material maintains its austenitic structure at both room and high temperatures, while improving strength and toughness. The addition of molybdenum significantly improves the material's resistance to pitting corrosion in chloride environments, while also enhancing its strength. The addition of boron refines the grains and increases grain boundary strength, thereby improving the material's toughness. The processing of stainless steel includes the following steps: using a dual melting technology of vacuum induction melting (VIM) and electroslag remelting (ESR) can achieve higher alloy homogeneity and purity. VIM melting in a vacuum environment effectively removes gaseous impurities and other harmful elements from the alloy, ensuring a purer metal composition. ESR further refines the metal through electroslag remelting, improving the alloy's uniformity and quality, resulting in a final product with higher standards in corrosion resistance and mechanical properties. A uniform austenitic single-phase microstructure is obtained by holding at 1050℃±10℃ for 1 hour followed by rapid water cooling. Rapid water cooling prevents grain growth and maintains the material's fine-grained structure.

[0054] This embodiment improves the corrosion resistance of the material by increasing the chromium and molybdenum content, reducing the risk of container failure. The addition of nickel enhances the strength and toughness of the metal, making it less prone to yielding or residual plastic deformation under pressure and impact. The addition of boron and nitrogen helps refine the grain size, improving the material's fatigue resistance and fracture resistance. Using this stainless steel as the metal liner material not only improves the container's strength, corrosion resistance, and fatigue performance, but also effectively solves the elastic mismatch problem between the metal liner and the CFRP winding layer, significantly improving the long-term stability and reliability of the composite material container.

[0055] In one embodiment, when the alloy material is stainless steel, the cumulative true plastic deformation matching the stainless steel includes: applying a cold stretch of 60-75% of the total deformation along the axial direction of the stainless steel bottle body to obtain the stainless steel after cumulative true plastic deformation.

[0056] Specifically, cold stretching is a strong plastic deformation process in which a large number of dislocations are generated within the material by applying 60-75% of the total deformation along the axial direction of the bottle. These dislocations can significantly increase the strength of the material. Through cold stretching, the ratio of the material's yield strength to its elastic modulus is significantly increased, thereby enhancing the material's plastic deformation capacity.

[0057] Accordingly, the isothermal aging of stainless steel includes: holding the stainless steel after cumulative true plastic deformation at a temperature of 340-360℃ for 0.3-0.7h to obtain isothermal aged stainless steel.

[0058] Specifically, under intermediate temperature conditions, boron and nitrogen elements in the material accumulate at grain boundaries, inducing the precipitation of Cr2N nanophases. These nanophases effectively stabilize the subcrystalline structure, further improving the material's strength and toughness. Short-duration intermediate-temperature aging treatment can lock in the subcrystalline structure formed during cold stretching, preventing grain growth during subsequent processing or use.

[0059] Correspondingly, the surface strengthening of stainless steel includes: using laser shock lithography to form a nanocrystalline layer with a thickness of 0.10–0.20 mm on the surface of isothermally aged stainless steel to obtain a metal liner; wherein the energy density of the laser shock lithography method is 8–12 J / cm². 2 The pulse width is 15–25 ns, and the number of pulses is 2–4.

[0060] Specifically, laser shock blasting can form a nanocrystalline region with a thickness of 0.10–0.20 mm on the material surface. The nanocrystalline structure exhibits higher strength and hardness, while significantly improving the material's fatigue resistance. Simultaneously, laser shock blasting introduces a residual compressive stress layer of approximately -350 MPa on the material surface. This residual compressive stress can significantly improve the material's fatigue resistance and crack propagation resistance.

[0061] In this embodiment, cold stretching, by applying 60-75% of the total deformation, enhances the strength and plasticity of the stainless steel, improves fatigue resistance and yield strain to 0.2%, effectively preventing yielding and residual plastic deformation of the metal liner during filling and discharging cycles. Isothermal aging further enhances the strength and toughness of the stainless steel, prevents grain growth, and ensures the stability of the material during cylinder use. The nanocrystalline layer formed by laser shock surface strengthening not only improves surface strength and fatigue resistance but also increases resistance to crack propagation, significantly extending the fatigue life of the metal liner. Ultimately, through the combination of these precise processes, the metal liner in the composite cylinder with the CFRP winding layer possesses higher strength, fatigue resistance, and toughness, effectively withstanding the high-pressure environment of filling and discharging cycles, ensuring the safety and service life of the cylinder.

[0062] In one embodiment, the titanium alloy comprises, by mass fraction: Nb: 20.0–26.0%, Zr: 2.5–5.0%, Sn: 6.0–9.5%, O: 0.25–0.45%, with the balance being Ti and unavoidable impurities.

[0063] Specifically, niobium is one of the main alloying elements in titanium alloys, expanding the β-phase region and improving the material's strength and toughness. High niobium content can significantly increase the material's strength, but excessively high niobium content may lead to a decrease in plasticity. Furthermore, the addition of niobium can improve the material's fatigue resistance. Zirconium can improve the material's creep resistance and high-temperature strength, as well as its oxidation resistance. Tin is a weakly β-phase stabilizing element, improving the material's strength and toughness, and also enhancing its fatigue resistance. By precisely controlling the content of niobium, zirconium, and tin, it is possible to improve the material's strength while maintaining good toughness and plasticity. Niobium and tin primarily provide β-phase stability, while zirconium improves the material's high-temperature performance.

[0064] This embodiment enhances the strength, toughness, and fatigue resistance of the titanium alloy by incorporating elements such as Nb, Zr, Sn, and O. The strengthening effect of Nb and Zr, in particular, improves the yield strength and tensile strength of the titanium alloy, while also enhancing its high-temperature performance. This allows the metal liner to withstand significant mechanical stress during inflation and deflation and effectively accommodates the elastic differences between itself and the CFRP winding layer. Furthermore, the high strength and good plasticity of the titanium alloy make the liner more stable during inflation and deflation cycles, reducing deformation and damage caused by elastic mismatch. Ultimately, the application of this titanium alloy material significantly improves the strength, fatigue resistance, and safety of the gas cylinder, extends its service life, and ensures the stability of the gas cylinder under complex operating conditions.

[0065] In one embodiment, the titanium alloy is subjected to homogenization heat treatment before the cumulative true plastic deformation treatment; wherein the conditions for homogenization heat treatment are: holding at a temperature of 1000 to 1020°C for 2 to 3 hours.

[0066] Specifically, during the casting process, titanium alloys may develop microstructural segregation, such as non-uniform composition and inconsistent grain size. This segregation affects the material's properties. Holding the alloy at a high temperature of 1000–1020°C promotes the diffusion of alloying elements, resulting in a more uniform microstructure. At high temperatures, the diffusion rate of alloying elements accelerates, effectively eliminating compositional segregation and forming a homogeneous solid solution. This is crucial for subsequent plastic deformation treatment, as a uniform microstructure improves the material's plasticity and toughness. Prolonged holding ensures uniform temperature within the material, allowing alloying elements to diffuse fully and distribute evenly. This helps eliminate compositional segregation and form a homogeneous solid solution.

[0067] In this embodiment, the titanium alloy undergoes homogenization heat treatment before cumulative true plastic deformation to eliminate microstructural segregation that may occur during casting, such as compositional inhomogeneity and inconsistent grain size. These segregations affect material properties. Holding at a high temperature of 1000–1020°C for 2–3 hours promotes the diffusion of alloying elements, further homogenizing the material's microstructure. Under high-temperature conditions, the diffusion rate of alloying elements accelerates, effectively eliminating compositional segregation and forming a uniform solid solution. A uniform microstructure is crucial for subsequent plastic deformation, improving the material's plasticity and toughness. Prolonged holding not only ensures uniform internal temperature but also allows for sufficient diffusion and uniform distribution of alloying elements, providing a better foundation for subsequent true plastic deformation and enhancing the overall performance of the titanium alloy.

[0068] In one embodiment, when the alloy material is a titanium alloy, the cumulative true plastic deformation matching the titanium alloy includes: cold rolling deformation of the titanium alloy with a thickness reduction of 85-92% to obtain a titanium alloy after cumulative true plastic deformation.

[0069] Specifically, cold rolling is a strong plastic deformation process that, by applying a thickness reduction of 85–92%, generates a large number of dislocations and distortion bands within the material. These defects provide defect-rich sites for subsequent ω-phase nucleation. Cold rolling deformation can significantly refine the grain size of the material, thereby improving its strength and toughness.

[0070] Accordingly, the isothermal aging of the titanium alloy includes: holding the titanium alloy after cumulative true plastic deformation at a temperature of 440-460℃ for 0.8-1.2h to precipitate a dispersed ω phase with a grain size of 5-15nm within the grains, thus obtaining the isothermal aged titanium alloy.

[0071] Specifically, under intermediate temperature conditions, alloying elements in the material precipitate to form metastable, dispersed ω-phase with a grain size of 5–15 nm. These dispersed phases are distributed within the grains and can effectively increase the 0.2% yield strain of the material. The precipitation of the dispersed ω-phase can significantly improve the yield strength of the material, thereby suppressing premature yielding behavior.

[0072] Correspondingly, the surface strengthening of the titanium alloy includes: using laser shock or shot peening to introduce a residual compressive stress layer of -300 to -500 MPa on the surface of the isothermally aged titanium alloy to obtain a metal liner.

[0073] Specifically, laser shock peening or shot peening can introduce a residual compressive stress layer of -300 to -500 MPa on the material surface. This residual compressive stress can significantly improve the material's fatigue resistance and crack propagation resistance.

[0074] In this embodiment, cold rolling deformation, with a thickness reduction of 85-92%, refines the grains and introduces dislocation structures, enhancing the fatigue resistance and crack propagation resistance of the titanium alloy, and reducing the yielding and plastic deformation of the metal liner during gas filling and discharging cycles. Subsequently, isothermal aging treatment promotes the precipitation of the ω phase, increasing the yield strain of the titanium alloy by 0.2%, enhancing the liner's resistance to external stress, and further alleviating the elastic mismatch between the metal liner and the CFRP winding layer. Finally, a residual compressive stress layer is introduced on the liner surface using laser shock peening or shot peening technology, significantly improving its fatigue resistance and crack propagation resistance, effectively preventing crack initiation and propagation. Combining these processes, the durability and safety of the titanium alloy liner during gas filling and discharging cycles are significantly improved, thereby effectively enhancing the overall performance and service life of the composite material container.

[0075] To better explain and facilitate understanding of this application, a detailed description of its specific embodiments is provided below. Unless otherwise specified in the embodiments, components are expressed as mass fractions, and all raw materials used in the embodiments of this application were purchased commercially.

[0076] Example 1: The alloy material used to prepare the metal liner is aluminum alloy: Mg: 4.5%, Mn: 0.5%, Cr: 0.15%, total Fe and Si: 0.18%, with the balance being Al.

[0077] Step S1: Heat the aluminum alloy to 460℃ and hold for 12 hours for annealing. (Please refer to...) Figure 1 This is an optical micrograph of the annealed aluminum alloy provided in Example 1 of this application. As can be seen from the figure, the annealed aluminum alloy exhibits a coarse equiaxed crystal morphology with an average grain size of approximately 80-120 μm.

[0078] Step S2 involves extruding the aluminum alloy through an ECAP die with a channel angle of 110° at room temperature for 6 passes to obtain the extruded aluminum alloy, thereby refining the grain size from the initial coarse state to 12-15μm.

[0079] Step S3 involves cryogenically rolling the extruded aluminum alloy under liquid nitrogen conditions at -196°C with a thickness reduction of 70%, yielding an aluminum alloy after cumulative true plastic deformation. Please refer to [link / reference]. Figure 2 This is a transmission electron micrograph of the aluminum alloy after cumulative true plastic deformation, provided in Example 1 of this application. As can be seen from the figure, a banded subgrain structure and high dislocation walls can be observed.

[0080] Step S4: Hold the aluminum alloy after cumulative true plastic deformation at 300℃ for 1 hour to obtain the aluminum alloy after isothermal aging. Step S5: The isothermal aged aluminum alloy is shot peened with a strength of 0.5 mmA to form a ZrO2 ceramic coating with a thickness of 0.25 mm on the surface, thus obtaining the metal liner.

[0081] The metal liner of Example 1 was evaluated using standard methods. The average grain size of the metal liner was less than 13 μm, and the yield strain was 0.2% (ε). 0.2 The tensile strength (σ) increased to 0.68%, and the tensile strength (σ) increased to 0.68%. b The pressure is approximately 335 MPa, and the elastic modulus (E) is approximately 70.2 GPa. It can operate stably for more than 20,000 cycles under cyclic charge-discharge conditions with working pressure of 20-85 MPa without leakage or significant residual strain accumulation.

[0082] Comparative Example 1: The alloy material used to prepare the metal liner is 6061T6 aluminum alloy: Mg: 0.8-1.2%, Si: 0.4-0.8%, Cu: 0.15-0.40%, Cr: 0.04-0.35%, Fe≤0.7%, Mn≤0.15%, Ti≤0.15%, Zn≤0.25%, with the balance being Al and unavoidable impurities.

[0083] The method for preparing the metal liner is as follows: solution treatment followed by artificial aging to T6 state, without cryogenic rolling or surface modification.

[0084] The metal liner of Comparative Example 1 was evaluated using standard methods. The grain size of the metal liner was 50–100 μm, with the strengthening phase β-Mg₂Si (100–500 nm) and low dislocation density. The yield strength σ was 0.2%. 0.2 ≈240~275MPa, elastic modulus (E) ≈69GPa. ε 0.2 =σ 0.2 / E≈0.35%~0.40%.

[0085] Comparing the metal liner of Example 1 and Comparative Example 1, the 0.2% yield strain of Example 1 is significantly higher than that of Comparative Example 1, an increase of approximately 0.3%. This indicates that processes such as equal channel corner extrusion, deep cryogenic rolling, and surface strengthening significantly improve the material's plastic deformation capacity. The grain size of Example 1 is significantly refined, which helps to improve the material's strength and toughness. The tensile strength of Example 1 is significantly higher than that of Comparative Example 1, an increase of approximately 60–95 MPa. This indicates that the material's strength has been significantly improved through process optimization. The elastic modulus of Example 1 is slightly higher than that of Comparative Example 1, but the difference is small. This indicates that the material's rigidity is slightly improved. Example 2: The alloy material used to prepare the metal liner is stainless steel, specifically stainless steel obtained through VIM-ESR duplex melting. Its main chemical composition is: C: 0.02%, Cr: 17.5%, Ni: 12.0%, Mo: 2.5%, N: 0.025%, B: 0.003%, with the balance being Fe.

[0086] Step S1: The stainless steel is heated to 1050℃ and held for 1 hour, then rapidly water-cooled to obtain a single-phase austenitic structure with uniform grains and no precipitated phase interference, ensuring the consistency and compositional uniformity of subsequent deformation.

[0087] Step S2: Apply cold stretching of 65% of the total deformation along the axial direction of the austenitic single-phase structure to obtain stainless steel after cumulative true plastic deformation.

[0088] Step S3: The stainless steel after cumulative true plastic deformation is held at 350℃ for 0.5h to obtain isothermal aged stainless steel.

[0089] Step S4, the isothermal aged stainless steel is subjected to an energy density of 10 J / cm³. 2 The surface is subjected to three pulsed laser treatments with a pulse width of 20ns to form a nanocrystalline layer with a thickness of 0.12mm on the surface. The grain size is controlled between 80-100nm. At the same time, a residual compressive stress of -350MPa is introduced into the surface layer to obtain a metal inner liner.

[0090] The metal liner of Example 2 was evaluated, and the test was conducted according to standard methods. The metal liner exhibited ε 0.2 ≈0.75%, σ b With mechanical properties of approximately 660 MPa and E≈198 GPa, it can maintain elastic stability under conditions of more than 21,000 cycles of inflation and deflation, and its performance is significantly better than that of traditional untreated 316L inner liner material (ε). 0.2 ≈0.30%.

[0091] Comparative Example 2: The alloy material used to prepare the metal liner is 316L stainless steel: Cr: 16.0~18.0%, Ni: 10.0~14.0%, Mo: 2.0~3.0%, C≤0.03%, Mn≤2.0%, Si≤0.75%, N≤0.10%, P≤0.045%, S≤0.030%, balance Fe.

[0092] Methods for preparing metal liner: annealing in the annealed state or after cold working, without involving nanocrystalline reinforcement or the introduction of residual compressive stress.

[0093] The metal liner of Comparative Example 2 was evaluated using standard methods. The grain size of the metal liner was 20–50 μm, the strengthening mechanism was solid solution strengthening, and there was no dispersed phase. 0.2 ≈205~290MPa, E≈185GPa. ε 0.2 ≈0.11%~0.16%.

[0094] Comparing the metal liner of Example 2 and Comparative Example 2, the 0.2% yield strain of Example 2 is significantly higher than that of Comparative Example 2, an increase of approximately 0.6%. This indicates that cold stretching, medium-temperature aging, and laser shock treatment significantly improve the material's plastic deformation capacity. The tensile strength of Example 2 is significantly higher than that of Comparative Example 2, an increase of approximately 370–455 MPa. This indicates that the material's strength is significantly improved through process optimization. The elastic modulus of Example 2 is slightly higher than that of Comparative Example 2, but the difference is small. This indicates a slight increase in the material's rigidity. The grain size of Example 2 is significantly refined, which contributes to improving the material's strength and toughness.

[0095] Example 3: The alloy material used to prepare the metal liner is a titanium alloy: Nb: 24%, Zr: 3.5%, Sn: 7.5%, O: 0.35%, with the balance being Ti.

[0096] Step S1: Heat the titanium alloy to 1000℃ and hold for 2.5h for homogenization heat treatment to obtain the homogenized heat-treated titanium alloy. Step S3: Perform 85% thickness compression deformation at room temperature to obtain the titanium alloy after cumulative true plastic deformation.

[0097] Step S4: The titanium alloy after cumulative true plastic deformation is held at 450℃ for 1 hour to precipitate a dispersed ω phase with a grain size of 5-15nm within the grains, thus obtaining the isothermal aged titanium alloy.

[0098] Step S5, the isothermal aged titanium alloy is subjected to an energy density of 11 J·cm⁻¹ -2A laser pulse with a pulse width of 15ns is used to impact the surface of the metal liner twice, generating a nanocrystalline layer with a thickness of about 0.15mm. The residual compressive stress on the surface reaches -480MPa, thus obtaining the metal liner.

[0099] The metal liner of Example 3 was evaluated, and the test was conducted according to standard methods. The ε of the metal liner was... 0.2 Reaching 2.9%, σ b ≈820MPa, E≈49GPa. This metal liner not only achieves a wide elastic platform while maintaining low modulus and lightweight, but also reduces its weight by about 27% compared to traditional aluminum alloy liners of the same volume, making it particularly suitable for applications with stringent mass-to-performance ratio requirements, such as aerospace and hydrogen energy.

[0100] In summary, this application achieves synergistic performance improvement by introducing high dislocation density, nano-precipitates, and residual compressive stress through cumulative plastic deformation, isothermal aging, and surface strengthening.

[0101] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0102] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

[0103] Although embodiments of this application have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of this application, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A method for preparing a metal liner to improve the fatigue life of a composite material container, characterized in that, The preparation method includes: An alloy material for preparing a metal liner is obtained; wherein the alloy material includes one of aluminum alloy, stainless steel, or titanium alloy; the alloy material is subjected to matched cumulative true plastic deformation, isothermal aging, and surface strengthening treatments to obtain the metal liner; wherein... When the alloy material is the aluminum alloy or the stainless steel, the 0.2% yield strain of the metal liner is not less than 0.60%; when the alloy material is the titanium alloy, the 0.2% yield strain of the metal liner is not less than 2.50%, and the elastic modulus is 45-55 GPa.

2. The preparation method according to claim 1, characterized in that, The aluminum alloy comprises, by mass fraction: Mg: 4.3-4.8%, Mn: 0.4-0.7%, Cr: 0.05-0.25%, Fe and Si total not exceeding 0.20%, with the balance being Al and unavoidable impurities, and simultaneously satisfying the following: a single impurity not exceeding 0.05%, and the total amount of impurities not exceeding 0.15%.

3. The preparation method according to claim 2, characterized in that, Before performing cumulative true plastic deformation treatment, the aluminum alloy is annealed; wherein the annealing conditions are: holding at a temperature of 455-465℃ for 12 hours.

4. The preparation method according to claim 2, characterized in that, When the alloy material is an aluminum alloy, the cumulative true plastic deformation of the aluminum alloy includes: The aluminum alloy is extruded 4 to 8 times at room temperature through a channel angle of 110° to obtain the extruded aluminum alloy. The extruded aluminum alloy is subjected to cryogenic rolling at a temperature of -196°C with a thickness reduction of 60-75%, to obtain an aluminum alloy after cumulative true plastic deformation. Accordingly, the isothermal aging of the aluminum alloy includes: holding the aluminum alloy after cumulative true plastic deformation at a temperature of 295-305°C for 0.8-1.2 hours to obtain the isothermal aged aluminum alloy; Accordingly, the surface strengthening of the aluminum alloy includes: shot peening the isothermally aged aluminum alloy with an intensity of 0.4 to 0.6 mmA to form a ZrO2 ceramic coating with a thickness of 0.20 to 0.30 mm on the surface, thereby obtaining the metal liner.

5. The preparation method according to claim 1, characterized in that, The stainless steel comprises, by mass fraction: C not more than 0.03%, Cr: 16.0-18.0%, Ni: 10.0-14.0%, Mo: 2.0-3.0%, N: 0.015-0.030%, B: 0.002-0.004%, with the balance being Fe and unavoidable impurities.

6. The preparation method according to claim 5, characterized in that, When the alloy material is stainless steel, the cumulative true plastic deformation matching the stainless steel includes: For the stainless steel bottle body, a cold stretching of 60-75% of the total deformation is applied along the axial direction of the bottle body to obtain stainless steel after cumulative true plastic deformation. Accordingly, the isothermal aging of the stainless steel includes: holding the stainless steel after cumulative true plastic deformation at a temperature of 340-360°C for 0.3-0.7 hours to obtain isothermal aged stainless steel; Accordingly, the surface strengthening of the stainless steel includes: using laser shock blasting to form a nanocrystalline layer with a thickness of 0.10–0.20 mm on the surface of the isothermally aged stainless steel to obtain the metal liner; wherein the energy density of the laser shock blasting is 8–12 J / cm². 2 The pulse width is 15–25 ns, and the number of pulses is 2–4.

7. The preparation method according to claim 1, characterized in that, The titanium alloy is measured by mass fraction Includes: Nb: 20.0–26.0%, Zr: 2.5–5.0%, Sn: 6.0–9.5%, O: 0.25–0.45%, with the balance being Ti and unavoidable impurities.

8. The preparation method according to claim 7, characterized in that, Before performing cumulative true plastic deformation treatment, the titanium alloy is subjected to homogenization heat treatment; wherein, the conditions for homogenization heat treatment are: holding at a temperature of 1000~1020℃ for 2~3h.

9. The preparation method according to claim 7, characterized in that, When the alloy material is a titanium alloy, the cumulative true plastic deformation of the titanium alloy includes: The titanium alloy is cold-rolled to reduce its thickness by 85-92% to obtain a titanium alloy after cumulative true plastic deformation. Accordingly, the isothermal aging of the titanium alloy includes: holding the titanium alloy after cumulative true plastic deformation at a temperature of 440-460℃ for 0.8-1.2h to obtain the isothermal aged titanium alloy; Accordingly, the surface strengthening of the titanium alloy includes: using laser shock or shot peening to introduce a residual compressive stress layer of -300 to -500 MPa on the surface of the isothermally aged titanium alloy to obtain the metal liner.

10. A metal liner for improving the fatigue life of composite material containers, characterized in that, The metal liner for improving the fatigue life of composite material containers is prepared using the method described in any one of claims 1-9.

11. A composite material container, characterized in that, The composite material container is obtained by winding a metal liner prepared by any one of the preparation methods described in claims 1-9 or by winding a metal liner and carbon fiber reinforced composite material as described in claim 10.

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