High mechanical fatigue resistance, nano-ceramic particle reinforced Al-Zn-Mg-Cu alloy and its preparation method

Abstract

This invention provides a high-mechanical-fatigue-resistance, nano-ceramic particle-reinforced Al-Zn-Mg-Cu alloy and its preparation method. The preparation method mainly includes: first, mixing titanium-niobium-aluminum alloy powder with B4C powder, B powder, and C powder to obtain a mixed powder; then, coating the mixed powder with pure aluminum strip to form a wire; and preparing an intermediate alloy wire containing nano-ceramic particles using plasma arc melting, electromagnetic stirring, and ultrasonic cavitation treatment; adding the wire to an Al-Zn-Mg-Cu alloy melt, followed by slag removal, casting, homogenization treatment, extrusion, and heat treatment to obtain the high-mechanical-fatigue-resistance, nano-ceramic particle-reinforced Al-Zn-Mg-Cu alloy. The high-mechanical-fatigue-resistance, nano-ceramic particle-reinforced Al-Zn-Mg-Cu alloy obtained by this invention achieves a fatigue life of 1-2 x 10⁻⁶ cycles under a stress ratio of 0.1, an experimental frequency of 80 Hz, and a stress of 350 MPa. 5 Under a stress of 250 MPa, the fatigue life reached 0.7–1.2 x 10⁻⁶ cycles. 7 The ultimate fatigue strength can reach 240-290 MPa, which is ≥17% higher than that of Al-Zn-Mg-Cu alloys obtained by existing technologies.

Description

Technical Field

[0001] This invention relates to the field of high-performance structural aluminum alloy materials, and particularly to Al-Zn-Mg-Cu alloys with high mechanical fatigue resistance and reinforced with nano-ceramic particles and their preparation methods. Background Technology

[0002] Al-Zn-Mg-Cu alloys are widely used in key areas such as aerospace critical load-bearing components, lightweight structures for rail transit, and new energy vehicle frames due to their excellent specific strength, good processing performance, and outstanding fracture toughness. As modern transportation and power equipment develops towards higher speeds, longer lifespans, and extreme lightweighting, more stringent requirements are placed on the mechanical fatigue resistance of materials under complex alternating loads during long-term service. However, traditional Al-Zn-Mg-Cu alloys exhibit insufficient resistance to fatigue damage in their microstructure under long-term alternating stress coupling, leading to prominent problems of fatigue fracture and drastic reduction in service life. Firstly, during cyclic service (mechanical fatigue), local plastic strain and dislocation slip become the main deformation and damage mechanisms. Dislocation pile-up at grain boundaries and the formation of stationary slip bands easily occur within the material, resulting in high local stress concentration. This makes fatigue microcracks highly likely to initiate early, causing the alloy's mechanical fatigue resistance to decrease significantly with each cycle. Secondly, to improve mechanical fatigue resistance and overall mechanical properties, existing technologies typically rely on further increasing the solid solution content of alloying elements such as Zn, Mg, and Cu in the matrix (high alloying) and adding Cr, or relying on a large amount of second-phase precipitation for strengthening, which is costly. Furthermore, under long-term alternating loads, coarse second-phase particles (such as coarse MgZn2 phase or undissolved iron-rich impurities) in this traditional composition can easily become fatigue crack initiation sources, leading to localized stress concentration and embrittlement, reducing material toughness and plasticity, significantly decreasing microstructural stability, and accelerating fatigue crack propagation. In terms of processing, existing technologies often employ complex pre-deformation and pre-aging treatments, relying on complex multi-round thermomechanical pretreatments and even more complex multi-pass heat treatments or severe plastic deformation processes. These processes involve cumbersome parameters, long time cycles, extremely high energy consumption, and poor repeatability, resulting in a sharp increase in the difficulty and manufacturing cost of large-format industrial-grade plates. Traditional methods of "high alloying" and "complex processes" have significant limitations, making it difficult to overcome the performance bottleneck of "the inability to simultaneously achieve high strength and high fatigue resistance," and failing to meet the ever-increasing demands for long service life in engineering projects. Therefore, developing a preparation method that reduces raw material addition costs, simplifies the process, and is easy to industrialize, in order to obtain Al-Zn-Mg-Cu alloys with excellent mechanical fatigue resistance, has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0003] To address the aforementioned technical challenges, this invention provides an Al-Zn-Mg-Cu alloy with high mechanical fatigue resistance and reinforced with nano-ceramic particles, comprising the following steps: (1) At room temperature, titanium-niobium-aluminum alloy powder is mixed with B4C powder, B powder and C powder in a mass ratio of 60-76:5-8:3-6:2-5 and the mixture is stirred at a speed of 15-45 r / min for 14-18 h to obtain powder mixture 1. The particle size of the titanium-niobium-aluminum alloy powder is 20-100 micrometers, the particle size of B4C powder is 10-60 micrometers, the particle size of B powder is 60-120 micrometers, and the particle size of C powder is 40-150 micrometers. (2) The powder mixture 1 obtained in step (1) is coated with pure aluminum strip to obtain wire A; the wire A is heated to 750-760℃ by plasma arc directional heating to melt it into a liquid flow, mixed with pure aluminum melt, electromagnetic stirring is applied, ultrasonic cavitation treatment is performed, and after casting and rolling, intermediate alloy wire B containing nano-ceramic particles is obtained. The plasma arc directional heating is performed at a power of 3-8 kW and a temperature of 720-760°C for 30-90 seconds; electromagnetic stirring is performed at a frequency of 500-1500 Hz and a current of 3000-8000 A for 30-300 seconds; ultrasonic cavitation treatment is performed at a power of 300-1000 W and a frequency of 20-150 kHz for 10-20 minutes; the powder mixture 1 accounts for 20%-40% of the mass of wire A; the wire A accounts for 22%-44% of the mass of pure aluminum melt; and the nano-ceramic particles in the intermediate alloy wire B containing nano-ceramic particles account for 0.2%-0.4% of the mass of intermediate alloy wire B. (3) The Al-Zn-Mg-Cu alloy is heated to 720-780℃ by increasing the power by 6-10kW every 8-13 minutes and held for 0.5-1.5h to obtain aluminum melt. Then, the intermediate alloy wire B containing nano-ceramic particles obtained in step (2) is added to the aluminum melt. The intermediate alloy wire B containing nano-ceramic particles accounts for 0.1%-0.3% of the mass of the aluminum melt until it is completely melted. Then, it is stirred at a stirring speed of 300-600r / min for 12-26min, and then stirred at a stirring speed of 0.6-2.4 The ingot is poured into the mold at a casting rate of kg / s to obtain an ingot. The obtained ingot is homogenized at 460-470℃ for 8-12 hours, then cooled to room temperature in the furnace, and then extruded at an extrusion temperature of 400-450℃ and an extrusion ratio of 10:1-25:1. After holding at 470-480℃ for 1-2 hours, it is water quenched, then held at 110-120℃ for 12-24 hours and air-cooled to room temperature to obtain a high mechanical fatigue resistance, nano-ceramic particle reinforced Al-Zn-Mg-Cu alloy. The Al-Zn-Mg-Cu alloy, by mass percentage, mainly comprises: Zn: 5.4-5.7 wt.%, Mg: 1.8-2.1 wt.%, Cu: 1.9-2.1 wt.%, Zr: ≤0.02 wt.%, Fe: ≤0.10 wt.%, Mn: ≤0.08 wt.%, Si: ≤0.08 wt.%, Ti: ≤0.04 wt.%, with the balance being Al; The high mechanical fatigue resistance, nano-ceramic particle-reinforced Al-Zn-Mg-Cu alloy contains 0.02wt.%-0.12wt.% nano-sized composite particles with a particle size of 70-120nm, uniformly dispersed within the aluminum alloy matrix. Under a stress ratio of 0.1 and an experimental frequency of 80Hz, the high mechanical fatigue resistance, nano-ceramic particle-reinforced Al-Zn-Mg-Cu alloy achieves a fatigue life of 1-2 x 10⁻⁶ cycles at a stress of 350 MPa. 5 Under a stress of 250 MPa, the fatigue life reached 0.7-1.2 x 10⁻⁶ cycles. 7 The ultimate fatigue strength can reach 240-290 MPa, which is ≥17% higher than the ultimate fatigue strength of Al-Zn-Mg-Cu alloys obtained by existing technologies.

[0004] Further, in step (1), at room temperature, titanium niobium aluminum alloy powder is mixed with B4C powder, B powder, and C powder in a mass ratio of 62-74:6-7:4-5:3-4; wherein the particle size of titanium niobium aluminum alloy powder is 24-96 micrometers, the particle size of B4C powder is 15-50 micrometers, the particle size of B powder is 65-110 micrometers, and the particle size of C powder is 35-140 micrometers.

[0005] Furthermore, the plasma arc directional heating described in step (2) is performed at a power of 4-7kW and a temperature of 725-755℃ for 35-85s, the electromagnetic stirring is performed at a frequency of 550-1400Hz and a current of 3600-7800A for 35-280s, and the ultrasonic cavitation treatment is performed at a power of 350-950W and a frequency of 25-140kHz for 12-18min.

[0006] Further, in step (2), the powder mixture 1 accounts for 25%-35% of the mass of wire A, the wire A accounts for 28%-36% of the mass of pure aluminum melt, and the nano-ceramic particles in the intermediate alloy wire B containing nano-ceramic particles account for 0.25%-0.35% of the mass of intermediate alloy wire B.

[0007] Further, in step (3), the Al-Zn-Mg-Cu alloy is heated to 725-775℃ by increasing the power by 7-9kW every 9-12 minutes and held for 0.6-1.2h to obtain aluminum melt.

[0008] Further, in step (3), the mixture is stirred at a stirring speed of 350-550 r / min for 13-24 min and then poured into the mold at a casting speed of 0.7-2.2 kg / s.

[0009] Further, in step (3), the process involves homogenization at 462-467℃ for 9-11 hours, followed by cooling to room temperature, extrusion at an extrusion temperature of 420-445℃, an extrusion ratio of 12:1-22:1, and an extrusion speed of 1-11 m / min, followed by water quenching at 472-478℃ for 1.2-1.8 hours, followed by heat treatment at 112-118℃ for 14-22 hours, and air cooling to room temperature to obtain a high mechanical fatigue resistance, nano-ceramic particle-reinforced Al-Zn-Mg-Cu alloy.

[0010] Further, the composition of the Al-Zn-Mg-Cu alloy mentioned in step (3) mainly includes: Zn: 5.55-5.65 wt.%, Mg: 1.95-2.05 wt.%, Cu: 1.95-2.05 wt.%, Zr: ≤0.02 wt.%, Fe: ≤0.9 wt.%, Mn: ≤0.07 wt.%, Si: ≤0.07 wt.%, Ti: ≤0.04 wt.%, with the balance being Al.

[0011] Furthermore, the Al-Zn-Mg-Cu alloy with high mechanical fatigue resistance and reinforced with nano-ceramic particles exhibits a fatigue life of 1.2-1.8 x 10⁻¹⁰ cycles under a stress ratio of 0.1, an experimental frequency of 80 Hz, and a stress of 350 MPa. 5 Under a stress of 250 MPa, the fatigue life reached 0.8-1.1 x 10⁻⁶ cycles. 7 The ultimate fatigue strength can reach 250-280 MPa, which is 19-25% higher than the ultimate fatigue strength of Al-Zn-Mg-Cu alloys obtained by existing technologies.

[0012] Compared with the prior art, the advantages of the present invention are: In terms of raw materials and proportions, this invention abandons the traditional approach of improving fatigue performance in high-strength aluminum alloys, which typically relies on increasing the content of strengthening elements such as Zn, Mg, and Cu, and adding additional precious metals or rare earth elements. This invention does not increase the content of strengthening elements such as Zn, Mg, and Cu, nor does it add Cr, thus controlling costs to a lower level. Regarding the process, existing research often employs complex multi-round thermomechanical pretreatments such as pre-deformation and pre-aging, as well as even more complex multi-pass heat treatment processes such as "solution + aging" or intense plastic deformation processes. These processes involve cumbersome parameters, long time cycles, extremely high energy consumption, and poor repeatability, leading to a sharp increase in the difficulty and manufacturing cost of producing large-format industrial plates. This invention eliminates the need for complex multi-round thermomechanical pretreatment and subsequent, more complex multi-pass "solution + aging" heat treatment processes. Instead, it utilizes in-situ melt control, nanoparticle dispersion strengthening, and a simple heat treatment process. By leveraging uniformly distributed nano-reinforcing phases to induce significant pinning and coordinated deformation at grain boundaries, subgrain boundaries, and within grains, it effectively suppresses dislocation pile-up, crack initiation, and crack propagation during fatigue cycles. This significantly simplifies the preparation process, reduces complexity, facilitates implementation, shortens time, and lowers energy consumption, resulting in substantial cost savings. The high mechanical fatigue resistance, nano-ceramic particle-reinforced Al-Zn-Mg-Cu alloy obtained by this invention features uniformly dispersed 70-120 nm nanocomposite particles within the aluminum alloy matrix, exhibiting good interfacial bonding and no visible defects, further enhancing overall mechanical properties. Ultimately, the high mechanical fatigue resistance, nano-ceramic particle-reinforced Al-Zn-Mg-Cu alloy obtained by this invention achieves a fatigue life of 1-2 x 10⁻⁶ cycles under a stress ratio of 0.1, an experimental frequency of 80 Hz, and a stress of 350 MPa. 5 Under a stress of 300 MPa, the fatigue life reached 0.7-1.2 x 10⁻⁶ cycles. 7 The ultimate fatigue strength can reach 240-290 MPa, which is ≥17% higher than that of Al-Zn-Mg-Cu alloys obtained by existing technologies. This invention achieves a significant improvement in the mechanical fatigue resistance of Al-Zn-Mg-Cu alloys through the interaction between nanoparticles and elements, the synergistic control of the ratio and process parameters. Under cyclic loading, it can effectively suppress the initiation and propagation of fatigue cracks. While maintaining good strength and plasticity, it achieves a simultaneous improvement in fatigue life, providing a reliable guarantee for the application of lightweight long-life structural materials in harsh service environments such as aerospace, high-speed rail transportation and high-end equipment. Attached Figure Description

[0013] Figure 1 The image shows the SN curve of Al-Zn-Mg-Cu alloy 1 with high mechanical fatigue resistance and nano-ceramic particle reinforcement in Example 2 of the present invention at a stress ratio of 0.1 and an experimental frequency of 80 Hz.

[0014] Figure 2 The image shows the SN curve of Al-Zn-Mg-Cu alloy 2 with high mechanical fatigue resistance and nano-ceramic particle reinforcement in Example 3 of the present invention at a stress ratio of 0.1 and an experimental frequency of 80 Hz.

[0015] Figure 3 The image shows the SN curve of Al-Zn-Mg-Cu alloy 3 in Comparative Example 1 of this invention at a stress ratio of 0.1 and an experimental frequency of 80 Hz.

[0016] Figure 4 The image shows the SN curve of the AA7050-T7451 aluminum alloy in Comparative Example 2 of this invention after T6 treatment, at a stress ratio of 0.1 and an experimental frequency of 80 Hz.

[0017] Figure 5 The image shows the SN curve of the AA7050-T7451 aluminum alloy in Comparative Example 2 of this invention after RRA treatment, at a stress ratio of 0.1 and an experimental frequency of 80 Hz.

[0018] Figure 6 The image shows the SN curve of AA7050-T7451 aluminum alloy after 1-CR treatment in Comparative Example 2 of this invention, at a stress ratio of 0.1 and an experimental frequency of 80 Hz.

[0019] Figure 7 The image shows the SN curve of the AA7050-T7451 aluminum alloy after T7451 treatment in Comparative Example 2 of this invention at a stress ratio of 0.1 and an experimental frequency of 80 Hz. Detailed Implementation Example 1

[0020] The preparation method of the intermediate alloy wire containing nano-ceramic particles includes the following steps: Step 1: At room temperature, titanium niobium aluminum alloy powder is mixed with B4C powder, B powder and C powder in a mass ratio of 70:6:4:3 and the mixture is stirred at a speed of 44 r / min for 15 h to obtain powder mixture 1. The particle size of the titanium-niobium-aluminum alloy powder is 32-85 micrometers, the particle size of B4C powder is 22-45 micrometers, the particle size of B powder is 72-107 micrometers, and the particle size of C powder is 30-130 micrometers. Step 2: Coat wire A with pure aluminum strip using the powder mixture 1 obtained in Step 1; melt wire A into a liquid flow by directional heating to 755°C using plasma arc, mix it with pure aluminum melt, then perform electromagnetic stirring, ultrasonic cavitation treatment, and casting and rolling to obtain intermediate alloy wire B containing nano-ceramic particles. The plasma arc directional heating is performed at a power of 5kW and a temperature of 750℃ for 70s. The electromagnetic stirring is performed at a frequency of 1000Hz and a current of 6000A for 210s. The ultrasonic cavitation treatment is performed at a power of 700W and a frequency of 80kHz for 15min. The powder mixture 1 accounts for 27% of the mass of wire A. The wire A accounts for 32% of the mass of pure aluminum melt. The nano-ceramic particles in the intermediate alloy wire B containing nano-ceramic particles account for 0.3% of the mass of intermediate alloy wire B. Example 2

[0021] A high-mechanical-fatigue-resistant Al-Zn-Mg-Cu alloy reinforced with nano-ceramic particles is prepared by the following steps: The Al-Zn-Mg-Cu alloy was heated to 750°C and held for 1 hour by increasing the power by 8kW every 10 minutes to obtain aluminum melt. Then, intermediate alloy wire B containing nano-ceramic particles obtained in Example 1 was added to the aluminum melt. The intermediate alloy wire B containing nano-ceramic particles accounted for 0.15% of the mass of the aluminum melt until it was completely melted. Then, it was stirred at a stirring speed of 400r / min for 17 min and then poured into a mold at a casting speed of 1.2 kg / s to obtain an ingot. The obtained ingot was homogenized at 465°C for 10 hours and then cooled to room temperature. Then, it was extruded at an extrusion temperature of 425°C, an extrusion ratio of 17:1, and an extrusion speed of 7 m / min. After holding at 475°C for 1.5 hours, it was water quenched, then held at 115°C for 18 hours and cooled to room temperature in air to obtain Al-Zn-Mg-Cu alloy 1 with high mechanical fatigue resistance and nano-ceramic particle reinforcement. The Al-Zn-Mg-Cu alloy, by mass percentage, mainly comprises: Zn: 5.57 wt.%, Mg: 2.00 wt.%, Cu: 1.98 wt.%, Zr: 0.01 wt.%, Fe: 0.08 wt.%, Mn: 0.06 wt.%, Si: 0.07 wt.%, Ti: 0.03 wt.%, with the balance being Al.

[0022] In this embodiment, the SN curve of the Al-Zn-Mg-Cu alloy 1 with high mechanical fatigue resistance and nano-ceramic particle reinforcement at a stress ratio of 0.1 and an experimental frequency of 80 Hz is shown below. Figure 1 As shown, under a stress of 350 MPa, the fatigue life of Al-Zn-Mg-Cu alloy 1, which exhibits high mechanical fatigue resistance and is reinforced with nano-ceramic particles, reaches 1.2 x 10⁻⁶ cycles. 5 Under a stress of 250 MPa, the fatigue life reached 0.9 x 10⁻⁶ cycles. 7The fatigue limit strength exceeded 245 MPa, demonstrating excellent resistance to mechanical fatigue. Example 3

[0023] The preparation method of the Al-Zn-Mg-Cu alloy 2, which exhibits high mechanical fatigue resistance and is reinforced with nano-ceramic particles, includes the following steps: The Al-Zn-Mg-Cu alloy was heated to 755℃ and held for 1.1h by increasing the power by 9kW every 11 minutes to obtain aluminum melt. Then, the intermediate alloy wire B containing nano-ceramic particles obtained in Example 1 was added to the aluminum melt. The intermediate alloy wire B containing nano-ceramic particles accounted for 0.25% of the mass of the aluminum melt until it was completely melted. Then, it was stirred at a stirring speed of 450r / min for 19 min and then poured into a mold at a casting speed of 1.7 kg / s to obtain an ingot. The obtained ingot was homogenized at 466℃ for 11h and then cooled to room temperature. Then, it was extruded at an extrusion temperature of 430℃, an extrusion ratio of 19:1, and an extrusion speed of 9 m / min. After holding at 476℃ for 1.6h, it was water quenched, then held at 117℃ for 20h and cooled to room temperature in air to obtain Al-Zn-Mg-Cu alloy 2 with high mechanical fatigue resistance and nano-ceramic particle reinforcement. The Al-Zn-Mg-Cu alloy, by mass percentage, mainly comprises: Zn: 5.57 wt.%, Mg: 2.00 wt.%, Cu: 1.98 wt.%, Zr: 0.01 wt.%, Fe: 0.08 wt.%, Mn: 0.06 wt.%, Si: 0.07 wt.%, Ti: 0.03 wt.%, with the balance being Al.

[0024] In this embodiment, the SN curve of the Al-Zn-Mg-Cu alloy 2 with high mechanical fatigue resistance and nano-ceramic particle reinforcement at a stress ratio of 0.1 and an experimental frequency of 80 Hz is as follows: Figure 2 As shown, under a stress of 350 MPa, the fatigue life of Al-Zn-Mg-Cu alloy 1, which exhibits high mechanical fatigue resistance and is reinforced with nano-ceramic particles, reaches 1.9 x 10⁻⁶ cycles. 5 Under a stress of 250 MPa, the fatigue life reached 1.1 x 10⁻⁶ cycles. 7 The fatigue limit strength exceeded 255 MPa, demonstrating excellent resistance to mechanical fatigue. Comparative Example 1

[0025] Al-Zn-Mg-Cu alloy 3, its preparation method includes the following steps: The Al-Zn-Mg-Cu alloy was heated to 750℃ by increasing the power by 8kW every 10 minutes and held for 1 hour to obtain aluminum molten metal. It was then poured into a mold at a casting speed of 1.2 kg / s to obtain an ingot. The obtained ingot was homogenized at 465℃ for 10 hours and then cooled to room temperature. Subsequently, it was extruded at an extrusion temperature of 425℃, an extrusion ratio of 17:1, and an extrusion speed of 7 m / min. After holding at 475℃ for 1.5 hours, it was water quenched, then held at 115℃ for 18 hours and cooled to room temperature in air to obtain Al-Zn-Mg-Cu alloy 3. The Al-Zn-Mg-Cu alloy, by mass percentage, mainly comprises: Zn: 5.57 wt.%, Mg: 2.00 wt.%, Cu: 1.98 wt.%, Zr: 0.01 wt.%, Fe: 0.08 wt.%, Mn: 0.06 wt.%, Si: 0.07 wt.%, Ti: 0.03 wt.%, with the balance being Al.

[0026] In this comparative example, Al-Zn-Mg-Cu alloy 3 and the Al-Zn-Mg-Cu alloy with high mechanical fatigue resistance and nano-ceramic particle reinforcement in the examples belong to the same type of seventh-series aluminum alloy, and are therefore comparable; the SN curve of Al-Zn-Mg-Cu alloy 2 obtained in this comparative example at a stress ratio of 0.1 and an experimental frequency of 80 Hz is as follows. Figure 2 As shown, under a stress of 350 MPa, the fatigue life of Al-Zn-Mg-Cu alloy plate 2 reaches 0.8 x 10⁻⁶ cycles. 5 Under a stress of 250 MPa, the fatigue life of Al-Zn-Mg-Cu alloy plate 2 reached 2.2 x 10⁻⁶ cycles. 6 The fatigue limit strength is close to 200 MPa.

[0027] The differences between Embodiments 2 and 3 of the present invention and Comparative Example 1 are as follows: In terms of raw material ratio, Example 2 added intermediate alloy wire containing nano-ceramic particles, while Comparative Example 1 did not. Regarding process parameters, the processing parameters for Example 2 were the same as those for Comparative Example 1. The Al-Zn-Mg-Cu alloy 1 with high mechanical fatigue resistance and nano-ceramic particle reinforcement obtained in Example 2 achieved a fatigue life of 1.2 x 10⁻⁶ cycles under a stress of 350 MPa. 5 The Al-Zn-Mg-Cu alloy 3 obtained in Comparative Example 1 achieved a fatigue life of 0.8 x 10^6 times under a stress of 350 MPa. 5 Under the same stress condition of 250 MPa, the fatigue life of Al-Zn-Mg-Cu alloy 1, which exhibits high mechanical fatigue resistance and is reinforced with nano-ceramic particles, approaches 0.9 x 10^10 times. 7The fatigue life of Al-Zn-Mg-Cu alloy 3 reached 2.2 x 10⁻⁶ cycles. 6 The fatigue life cycles of the two alloys differed by a factor of four. It can be seen that, regardless of low-cycle or high-cycle conditions, the fatigue life of the high mechanical fatigue resistance, nano-ceramic particle-reinforced Al-Zn-Mg-Cu alloy 1 (Example 2) is superior to that of Al-Zn-Mg-Cu alloy 3, and the fatigue limit strength of the present invention is also higher. Therefore, the high mechanical fatigue resistance, nano-ceramic particle-reinforced Al-Zn-Mg-Cu alloy 1 obtained in Example 2 exhibits significantly better mechanical fatigue resistance than the Al-Zn-Mg-Cu alloy 3 obtained in Comparative Example 1, and its durability under repeated loading conditions is superior.

[0028] Example 3 incorporated an intermediate alloy wire containing nano-ceramic particles. Although the processing flow was the same as in Comparative Example 1, the specific process parameters differed. The Al-Zn-Mg-Cu alloy 2 obtained in Example 3, with high mechanical fatigue resistance and reinforced with nano-ceramic particles, achieved a fatigue life of 1.9 x 10⁻⁶ cycles under a stress of 350 MPa. 5 The Al-Zn-Mg-Cu alloy 3 obtained in Comparative Example 1 achieved a fatigue life of 0.8 x 10^6 times under a stress of 350 MPa. 5 Under the same stress condition of 250 MPa, the fatigue life of the Al-Zn-Mg-Cu alloy 2, which exhibits high mechanical fatigue resistance and is reinforced with nano-ceramic particles, approaches 1.1 x 10^6 times. 7 The fatigue life of Al-Zn-Mg-Cu alloy 3 reached 2.2 x 10^3 times. 6 The fatigue life cycles of the two alloys differed by a factor of five. It can be seen that, regardless of low-cycle or high-cycle conditions, the fatigue life of the high-mechanical-fatigue-resistance, nano-ceramic particle-reinforced Al-Zn-Mg-Cu alloy 2 is superior to that of the Al-Zn-Mg-Cu alloy 3. Furthermore, the fatigue limit strength of this invention is higher. Therefore, the high-mechanical-fatigue-resistance, nano-ceramic particle-reinforced Al-Zn-Mg-Cu alloy 2 obtained in Example 3 exhibits significantly better mechanical fatigue resistance than the Al-Zn-Mg-Cu alloy 3 obtained in Comparative Example 1, and the durability performance of this invention under repeated loading conditions is superior. Comparative Example 2

[0029] In their article "The Influence of Micro-deformation After Pre-aging on the Fatigue Properties of 7050 Aluminum Alloy," Zhang et al. investigated the fatigue properties of the alloy by performing micro-deformation after pre-aging and finally aging it. AA7050-T7451 aluminum alloy was first solution-treated at 475℃ for 10 h, followed by pre-aging at 80℃ for 6 h. Subsequently, it underwent micro-deformation treatment by cold rolling with a 5% deformation amount using a twin-roll mill. After micro-deformation, it was aged at 120℃ for 10 h to obtain 7050 aluminum alloy in 1-CR service condition. The composition of AA7050-T7451 aluminum alloy, by mass percentage, mainly includes: Zn: 5.8 wt.%, Mg: 2.2 wt.%, Cu: 2.3 wt.%, Zr: 0.04 wt.%, Fe: 0.15 wt.%, Mn: 0.10 wt.%, Si: 0.12 wt.%, Ti: 0.06 wt.%, Cr: 0.12 wt.%, with the balance being Al.

[0030] The SN curves of the AA7050-T7451 aluminum alloy obtained in this comparative example after T6 treatment at a stress ratio of 0.1 and an experimental frequency of 80Hz are as follows: Figure 4 As shown, its fatigue life reaches 0.6 x 10⁻⁶ cycles under a stress of 350 MPa. 5 Furthermore, under a stress condition of 250 MPa, its fatigue life reached 2.6 x 10^6 times. 5 The SN curves after RRA treatment at a stress ratio of 0.1 and an experimental frequency of 80 Hz are shown below. Figure 5 As shown, its fatigue life reaches 0.8 x 10⁻⁶ cycles under a stress of 350 MPa. 5 Furthermore, under a stress condition of 250 MPa, its fatigue life also reaches 1.8 x 10^6 times. 5 The SN curves after 1-CR treatment at a stress ratio of 0.1 and an experimental frequency of 80 Hz are shown below. Figure 6 As shown, its fatigue life reaches 0.9 x 10⁻⁶ cycles under a stress of 350 MPa. 5 Under a stress of 250 MPa, its fatigue life reached 2.4 x 10^6 times. 6 Secondly, its ultimate fatigue strength exceeds 200 MPa. The SN curves after T7451 treatment at a stress ratio of 0.1 and an experimental frequency of 80 Hz are shown below. Figure 7 As shown, its fatigue life reaches 0.5 x 10⁻⁶ cycles under a stress of 350 MPa. 5 Furthermore, under a stress of 250 MPa, its fatigue life reached 1.2 x 10^6 times. 5 Second-rate.

[0031] The difference between Example 2 and Comparative Example 2 is: The high mechanical fatigue resistance, nano-ceramic particle-reinforced Al-Zn-Mg-Cu alloy 1 in Example 2 of this invention and the AA7050-T7451 aluminum alloy in Comparative Example 2 both belong to the same type of VII series aluminum alloys, and are therefore comparable. The proportion of alloying elements in the high mechanical fatigue resistance, nano-ceramic particle-reinforced Al-Zn-Mg-Cu alloy 1 obtained in Example 2 (9.80 wt.%) is lower than that in Comparative Example 2 (10.88 wt.%). In particular, the contents of metallic elements such as Zn (5.57 wt.%), Mg (2.00 wt.%), Cu (1.98 wt.%), and Mn (0.06 wt.%) in Example 2 are all lower than those in Comparative Example 2 (5.8 wt.%), Mg (2.2 wt.%), Cu (2.3 wt.%), and Mn (0.10 wt.%). The content of Cr in Example 2 is as follows: Compared with Comparative Example 2, no Cr element was added, which saved costs. At the same time, the preparation process of the service state of the Al-Zn-Mg-Cu alloy 1 with high mechanical fatigue resistance and nano-ceramic particle reinforcement obtained in Example 2 (water quenching after holding at 475℃ for 1.5h, and then holding at 115℃ for 18h) is simpler and less complex than the preparation process of the four service states (T6, RRA, 1-CR, T7451) in Comparative Example 2. In particular, the service state with the best mechanical fatigue resistance in Comparative Example 2—the 1-CR service state—has the following preparation process: first, solution treatment at 475℃ for 10h, then pre-aging treatment at 80℃ for 6h, followed by micro-deformation treatment with 5% deformation by cold rolling through a twin-roll mill, and then aging treatment at 120℃ for 10h. Example 2 does not rely on complex multi-round thermomechanical pretreatment, nor does it involve complex multi-pass subsequent heat treatment. Compared with Example 2, the preparation process of Comparative Example 2 is more cumbersome, time-consuming, and energy-intensive. Moreover, under the same test conditions, the Al-Zn-Mg-Cu alloy 1 with high mechanical fatigue resistance and nano-ceramic particle reinforcement obtained in Example 2, in the service state with the best mechanical fatigue resistance in Comparative Example 2—the 1-CR service state—did not reach 0.9 x 10^6 fatigue cycles under a stress of 350 MPa. 5 Furthermore, the Al-Zn-Mg-Cu alloy 1 with high mechanical fatigue resistance and reinforced with nano-ceramic particles obtained in Example 2 achieved a fatigue life of 1.2 x 10^6 cycles under a stress of 350 MPa. 5 Similarly, under a stress condition of 250 MPa, the fatigue life of the 1-CR service condition in Comparative Example 2 reached 2.4 x 10^6 times. 6 The fatigue life of Al-Zn-Mg-Cu alloy 1, which exhibits high mechanical fatigue resistance and is reinforced with nano-ceramic particles, reached 0.9 x 10⁻⁶ cycles. 7The fatigue life of the alloy obtained in Example 2 is nearly four times higher than that of Comparative Example 2. Furthermore, while the ultimate fatigue strength of the 1-CR alloy in Comparative Example 2 under service conditions is around 200 MPa, the fatigue ultimate strength of the Al-Zn-Mg-Cu alloy 1 with high mechanical fatigue resistance and reinforced with nano-ceramic particles obtained in Example 2 exceeds 245 MPa. Compared with the prior art, the ultimate fatigue strength of this invention is improved by ≥17%, demonstrating superior resistance to mechanical fatigue. This indicates that the Al-Zn-Mg-Cu alloy with high mechanical fatigue resistance and reinforced with nano-ceramic particles obtained in this invention achieves excellent improvement in resistance to mechanical fatigue under conditions of lower alloy cost and lower cost than the prior art.

[0032] In summary, compared with the comparative examples and existing technologies, this invention reduces the total amount of alloying elements added (especially Zn, Mg, and Cu metal elements in the embodiments) and does not add Cr, thus reducing costs. Meanwhile, Comparative Example 2 requires pre-deformation, pre-aging treatment, and complex multi-pass "deformation + solution + aging" processes to improve microstructure and fatigue performance. This process is not only cumbersome and energy-intensive, but also makes it difficult to control the microstructure uniformity in large-size aluminum alloy components. In contrast, this invention does not rely on complex multi-round thermomechanical pretreatment or complex multi-pass subsequent heat treatment. It utilizes in-situ melt control and nanoparticle dispersion strengthening processes, along with a simple heat treatment process, to leverage the uniformly distributed nano-reinforcing phase to generate significant pinning and coordinated deformation effects at grain boundaries, subgrain boundaries, and within grains. This effectively suppresses dislocation pile-up, crack initiation, and crack propagation during fatigue cycling. By designing alloy components, synergistic effects of elements, adjusting the ratio of reinforcing phases, and synergistically controlling the process and process parameters, the preparation process is significantly simplified and the complexity of the process is reduced. Even without complex grain boundary engineering treatments, it still achieves superior fatigue damage resistance and fatigue life compared to existing technologies. The material of this invention achieves improved mechanical fatigue resistance, significantly increasing its service life and reliability under alternating loads and complex service environments, possessing good engineering application value and industrialization prospects. This invention breaks through the technical bottleneck of limited fatigue life and insufficient crack propagation resistance of existing aluminum alloy materials under cyclic loading conditions, achieving improved fatigue resistance. It should be noted that the alloy components, element ratios, and process parameters differ in the various embodiments of this invention, resulting in significantly different fatigue properties. The above results indicate that the performance improvement of the material of this invention does not depend on a single alloying element, a single reinforcing phase, or a single process parameter, but rather originates from the combined effect of multi-component coupling, ratio optimization, nanoparticle regulation, and synergistic control of process parameters. Only when the various factors are effectively matched and synergistically controlled within the scope of the claims of this invention can excellent comprehensive fatigue resistance be obtained.

Claims

1. A high-mechanical-fatigue-resistant, nano-ceramic particle-reinforced Al-Zn-Mg-Cu alloy, characterized in that, Its preparation method includes the following steps: (1) At room temperature, titanium-niobium-aluminum alloy powder is mixed with B4C powder, B powder and C powder in a mass ratio of 60-76:5-8:3-6:2-5 and the mixture is stirred at a speed of 15-45 r / min for 14-18 h to obtain powder mixture 1. The particle size of the titanium-niobium-aluminum alloy powder is 20-100 micrometers, the particle size of B4C powder is 10-60 micrometers, the particle size of B powder is 60-120 micrometers, and the particle size of C powder is 40-150 micrometers. (2) The powder mixture 1 obtained in step (1) is coated with pure aluminum strip to obtain wire A; the wire A is heated to 750-760℃ by plasma arc directional heating to melt it into a liquid flow, mixed with pure aluminum melt, electromagnetically stirred, ultrasonically cavitated, and cast and rolled to obtain intermediate alloy wire B containing nano-ceramic particles. The plasma arc directional heating is performed at a power of 3-8 kW and a temperature of 720-760°C for 30-90 seconds; electromagnetic stirring is performed at a frequency of 500-1500 Hz and a current of 3000-8000 A for 30-300 seconds; ultrasonic cavitation treatment is performed at a power of 300-1000 W and a frequency of 20-150 kHz for 10-20 minutes; the powder mixture 1 accounts for 20%-40% of the mass of wire A; the wire A accounts for 22%-44% of the mass of pure aluminum melt; and the nano-ceramic particles in the intermediate alloy wire B containing nano-ceramic particles account for 0.2%-0.4% of the mass of intermediate alloy wire B. (3) The Al-Zn-Mg-Cu alloy is heated to 720-780℃ by increasing the power by 6-10kW every 8-13 minutes and held for 0.5-1.5h to obtain aluminum melt. Then, the intermediate alloy wire B containing nano-ceramic particles obtained in step (2) is added to the aluminum melt. The intermediate alloy wire B containing nano-ceramic particles accounts for 0.1%-0.3% of the mass of the aluminum melt until it is completely melted. Then, it is stirred at a stirring speed of 300-600r / min for 12-26 min and then poured into a mold at a casting speed of 0.6-2.4 kg / s to obtain an ingot. The obtained ingot is homogenized at 460-470℃ for 8-12h and then cooled to room temperature. Subsequently, it is extruded at a temperature of 400-450℃, an extrusion ratio of 10:1-25:1, and a casting speed of 0.5-12 The Al-Zn-Mg-Cu alloy with high mechanical fatigue resistance and nano-ceramic particles is obtained by extrusion at a speed of m / min, holding at 470-480℃ for 1-2 hours, water quenching, holding at 110-120℃ for 12-24 hours, and air cooling to room temperature. The Al-Zn-Mg-Cu alloy, by mass percentage, mainly comprises: Zn: 5.40-5.70 wt.%, Mg: 1.80-2.10 wt.%, Cu: 1.90-2.10 wt.%, Zr: ≤0.03 wt.%, Fe: ≤0.10 wt.%, Mn: ≤0.08 wt.%, Si: ≤0.08 wt.%, Ti: ≤0.05 wt.%, with the balance being Al; The high mechanical fatigue resistance, nano-ceramic particle-reinforced Al-Zn-Mg-Cu alloy contains 0.02wt.%-0.12wt.% nano-sized composite particles with a particle size of 70-120nm, uniformly dispersed within the aluminum alloy matrix. Under a stress ratio of 0.1 and an experimental frequency of 80Hz, the high mechanical fatigue resistance, nano-ceramic particle-reinforced Al-Zn-Mg-Cu alloy achieves a fatigue life of 1-2 x 10⁻⁶ cycles at a stress of 350 MPa. 5 Under a stress of 250 MPa, the fatigue life reached 0.7-1.2 x 10⁻⁶ cycles. 7 The ultimate fatigue strength can reach 240-290 MPa, which is ≥17% higher than the ultimate fatigue strength of Al-Zn-Mg-Cu alloys obtained by existing technologies.

2. The Al-Zn-Mg-Cu alloy with high mechanical fatigue resistance and reinforced with nano-ceramic particles according to claim 1, characterized in that, In step (1), at room temperature, titanium niobium aluminum alloy powder is mixed with B4C powder, B powder, and C powder in a mass ratio of 62-74:6-7:4-5:3-4; wherein the particle size of titanium niobium aluminum alloy powder is 24-96 micrometers, the particle size of B4C powder is 15-50 micrometers, the particle size of B powder is 65-110 micrometers, and the particle size of C powder is 35-140 micrometers.

3. The Al-Zn-Mg-Cu alloy with high mechanical fatigue resistance and reinforced with nano-ceramic particles according to claim 1, characterized in that, The plasma arc directional heating described in step (2) is heated at a temperature of 725-755℃ for 35-85s with a power of 4-7kW, the electromagnetic stirring is stirred at a frequency of 550-1400Hz with a current of 3600-7800A for 35-280s, and the ultrasonic cavitation treatment is treated at a power of 350-950W with a frequency of 25-140kHz for 12-18min.

4. The Al-Zn-Mg-Cu alloy with high mechanical fatigue resistance and reinforced with nano-ceramic particles according to claim 1, characterized in that, In step (2), the powder mixture 1 accounts for 25%-35% of the mass of wire A, the wire A accounts for 28%-36% of the mass of pure aluminum melt, and the nano-ceramic particles in the intermediate alloy wire B containing nano-ceramic particles account for 0.25%-0.35% of the mass of intermediate alloy wire B.

5. The Al-Zn-Mg-Cu alloy with high mechanical fatigue resistance and reinforced with nano-ceramic particles according to claim 1, characterized in that, In step (3), the Al-Zn-Mg-Cu alloy is heated to 725-775℃ by increasing the power by 7-9kW every 9-12 minutes and held for 0.6-1.2h to obtain aluminum melt.

6. The Al-Zn-Mg-Cu alloy with high mechanical fatigue resistance and reinforced with nano-ceramic particles according to claim 1, characterized in that, In step (3), the mixture is stirred at a stirring speed of 350-550 r / min for 13-24 min and then poured into the mold at a casting speed of 0.7-2.2 kg / s.

7. The Al-Zn-Mg-Cu alloy with high mechanical fatigue resistance and reinforced with nano-ceramic particles according to claim 1, characterized in that, The process described in step (3) involves homogenization treatment at 462-467℃ for 9-11 hours, followed by cooling to room temperature. Then, the material is extruded at an extrusion temperature of 420-445℃, an extrusion ratio of 12:1-22:1, and an extrusion speed of 1-11 m / min. After holding at 472-478℃ for 1.2-1.8 hours, the material is water-quenched, then held at 112-118℃ for 14-22 hours, and finally cooled to room temperature in air to obtain a high mechanical fatigue resistance, nano-ceramic particle-reinforced Al-Zn-Mg-Cu alloy.

8. The Al-Zn-Mg-Cu alloy with high mechanical fatigue resistance and reinforced with nano-ceramic particles according to claim 1, characterized in that, The composition of the Al-Zn-Mg-Cu alloy mentioned in step (3) mainly includes: Zn: 5.55-5.65 wt.%, Mg: 1.95-2.05 wt.%, Cu: 1.95-2.05 wt.%, Zr: ≤0.02 wt.%, Fe: ≤0.9 wt.%, Mn: ≤0.07 wt.%, Si: ≤0.07 wt.%, Ti: ≤0.04 wt.%, with the balance being Al.

9. The Al-Zn-Mg-Cu alloy with high mechanical fatigue resistance and reinforced with nano-ceramic particles according to claim 1, characterized in that, A high-mechanical-fatigue-resistance Al-Zn-Mg-Cu alloy reinforced with nano-ceramic particles achieved a fatigue life of 1.2-1.8 x 10⁻⁶ cycles under a stress ratio of 0.1, an experimental frequency of 80 Hz, and a stress of 350 MPa. 5 Under a stress of 250 MPa, the fatigue life reached 0.8-1.1 x 10⁻⁶ cycles. 7 The ultimate fatigue strength can reach 250-280 MPa, which is 19-25% higher than the ultimate fatigue strength of Al-Zn-Mg-Cu alloys obtained by existing technologies.

Images