High-toughness anti-fatigue aluminum alloy and preparation method thereof

Abstract

The invention belongs to the technical field of aluminum alloys, and particularly relates to a high-toughness anti-fatigue aluminum alloy and a preparation method thereof. The alloy comprises the following components in percentage by mass: 0.6-1.4% of Mg, 0.6-1.4% of Si, 0.5-1% of Mn, 0.3-0.8% of Cu, 0.1-0.4% of Cr, 0.1-0.3% of Mo, less than or equal to 0.15% of Fe, less than or equal to 0.05% of Ti, less than or equal to 0.05% of other impurities and the balance of Al. In the alloy, the ratio of Mn to (Cr + Mo) is 2-5, and Cr + Mo is less than or equal to 0.4. The aluminum alloy is subjected to synergistic microalloying of elements Mn, Cr and Mo and three-stage homogenization treatment, then a high-density'core-shell 'structure dispersed phase is separated out, and the deformation structure regulation and control effect is effectively improved; through hot forging and multi-stage solution treatment, a mixed crystal structure in which sub-crystals and recrystallization coexist is obtained, the fatigue crack propagation rate is remarkably reduced, and the obdurability and the fatigue resistance are synchronously improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aluminum alloy, and particularly relates to a high-strength and high-toughness anti-fatigue aluminum alloy and a preparation method thereof. BACKGROUND

[0002] High-performance lightweight alloy materials are an important way to realize automobile lightweighting. Aluminum alloys are highly concerned by the automobile industry at home and abroad due to their medium-high strength, good formability and corrosion resistance. Among them, Al-Mg-Si-Cu series wrought alloys and Al-Si series cast alloys are most widely used. The safety-critical load-bearing components such as automobile chassis and frame have strict requirements on the performance of aluminum alloy materials. The materials not only need to have high strength to enhance the resistance to deformation, but also need to have excellent anti-fatigue performance to improve the ability to resist dynamic load and ensure the service safety of the components under complex alternating load. Therefore, the preparation of high-strength and high-toughness anti-fatigue alloy is a hot issue in the field of high-performance aluminum alloy research. Aluminum alloy has high stacking fault energy, and is prone to severe recrystallization during hot working.

[0003] Chinese patent CN103589977A provides a method for improving the fatigue performance of Al-Cu-Mg alloy. The main process is: after homogenization treatment, the aluminum alloy is sequentially subjected to high-temperature rolling, primary solid solution treatment, large deformation cold rolling, secondary solid solution treatment and natural aging treatment, so that the alloy forms more recrystallized texture, thereby improving the anti-fatigue performance of the alloy.

[0004] Chinese patent CN112725711A provides a method for improving the fatigue performance of high-strength aluminum alloy. The main process is: before solid solution treatment of the aluminum alloy rod, the aluminum alloy is heated to a certain temperature, and the aluminum alloy rod is clamped at both ends by a clamp for one or more times of torsion treatment to refine the structure and obtain aluminum alloy with higher anti-fatigue performance.

[0005] Chinese patent CN113151758A discloses an Al-Mg-Si series aluminum alloy with excellent fatigue resistance and a preparation method thereof. The alloy texture characteristics are controlled, and creep aging and artificial aging are combined to improve the fatigue resistance of the alloy.

[0006] The above-mentioned aluminum alloys and preparation methods thereof disclosed in the patents, and other technologies disclosed in the prior art for improving the anti-fatigue performance of Al-Cu, Al-Mg-Si series wrought aluminum alloys, mainly realize the improvement of the anti-fatigue performance through recrystallization and other means caused by plastic deformation processing. However, the high stacking fault energy characteristics of aluminum alloy lead to the occurrence of dynamic recovery during hot mechanical processing, and the alloy is prone to recrystallization and abnormal grain growth during subsequent annealing treatment, forming a single coarse grain structure, which reduces the strength and toughness of the alloy and the anti-fatigue performance. It can be seen that the microstructure control during the preparation of the alloy is the key to realizing high strength, high toughness and high anti-fatigue performance.

[0007] Therefore, it is of important practical significance and value to develop a new processing method for effectively inhibiting the fatigue crack propagation rate of 6XXX series aluminum alloy, especially for products suitable for large-scale engineering applications and experiencing long process thermal mechanical processing, and having the mixed crystal structure characteristics of subgrain and recrystallization coexistence, while ensuring high strength, high toughness and high fatigue resistance. The present application is proposed to fill this technical gap. SUMMARY

[0008] In order to solve the above-mentioned technical problems, the present application provides the following technical solutions: The present application provides a preparation method of high-strength and high-toughness anti-fatigue aluminum alloy, comprising the following steps: S11: Melting and semi-continuous casting of aluminum, copper, magnesium and intermediate alloy to obtain an ingot; the ingot comprises the following elements by weight percentage: 0.6-1.4% Mg, 0.6-1.4% Si, 0.5-1.0% Mn, 0.3-0.8% Cu, 0.1-0.4% Cr, 0.1-0.3% Mo, Fe not more than 0.15%, Ti not more than 0.05%, and the total amount of other unavoidable impurities not more than 0.05%, with the balance being Al; wherein the sum of Cr and Mo is not more than 0.4%, and the mass ratio of Mn to the sum of Cr and Mo is 2-5:1; S12: Multi-stage homogenization heat treatment of the ingot; after the multi-stage homogenization heat treatment, the ingot precipitates α-Al(Mn,Cr,Mo)Si dispersed phase; S13: Hot forging treatment of the ingot after the multi-stage homogenization heat treatment; S14: Solid solution heat treatment of the ingot after the hot forging; S15: Artificial aging heat treatment of the ingot after the solid solution heat treatment to obtain the high-strength and high-toughness anti-fatigue aluminum alloy.

[0009] The present application aims to break through the technical problems of the prior art and provide a high-strength and high-toughness anti-fatigue 6XXX series aluminum alloy and a preparation method thereof, so as to form a large number of fine and uniformly distributed dispersed phases in the aluminum alloy structure, have the mixed crystal structure characteristics of subgrain and recrystallization coexistence, and simultaneously ensure the synchronous improvement of the strength, toughness and fatigue strength of the 6XXX series aluminum alloy.

[0010] Preferably, the intermediate alloy is selected from AlSi20, AlMn10, AlMo5 and AlCr10.

[0011] Preferably, the steps of melting and semi-continuous casting are as follows: (1) After batching, Al and AlSi20 are heated to 750-760 ℃ for melting; (2) adding AlMn10, AlMo5 and AlCr10 into the molten material, holding at 750-760 ℃ for 10-20 min; (3) lowering the melt to 720 ℃, adding pure Cu and pure Mg, refining at 730-750 ℃ for 10-20 min under inert atmosphere; (4) performing slagging treatment on the melt and holding for 12-18 min; (5) lowering to 720-730 ℃ and casting to obtain the ingot.

[0012] Specifically, the steps of melting and semi-continuous casting are as follows: (1) dosing according to the alloy composition; (2) placing pure Al and AlSi20 intermediate alloy into the smelting furnace, setting the furnace temperature at 750-760 ℃ until all raw materials are completely melted; (3) sequentially adding AlMn10, AlMo5 and AlCr10 intermediate alloy until completely melted, holding the melt for 10-20 min; (4) sequentially adding pure Cu and pure Mg when the melt temperature drops to 720 ℃; (5) increasing the furnace temperature to 730-750 ℃ for refining, using high-purity argon to degas the high-temperature melt for 10-20 min, then performing slagging treatment, and then holding the melt for 12-18 min; (6) when the furnace temperature drops to 720-730 ℃, casting the melt into the desired alloy ingot.

[0013] Preferably, in the step S12, the precipitated α-Al(Mn,Cr,Mo)Si dispersed phase is in core-shell structure, the number density is 10 21 -10 22 m -3 , the average equivalent diameter is less than 250.0 nm, and the dispersed phase free zone (DFZ) width is within 2.00 μm.

[0014] Preferably, in the step S12, the steps of multi-stage homogenization heat treatment are as follows: S21: holding the ingot at a temperature of 380-420 ℃ for 2-6 h; S22: holding the ingot at a temperature of 450-500 ℃ for 1-4 h; S23: holding the ingot at a temperature of 530-570 ℃ for 6-12 h and then cooling to room temperature (25±5 ℃); in the steps S21-S23, the heating rate is 0.5-5.0 ℃ / min.

[0015] Preferably, in the step S13, the hot forging treatment is as follows: S31: preheat the hot forging equipment hammer head to 400-425 DEG C, the heating mode of the hot forging equipment hammer head is resistance heating; the multi-stage homogenization heat treated ingot is kept at 450-530 DEG C for 0.5-2 h; S32: cool the ingot to room temperature after the hot forging; the speed of the hot forging is 10-50 mm / s, and the deformation is 50-70%.

[0016] Further, the time from the hot forging to the cooling is less than 5 s.

[0017] Preferably, in the step S14, the solid solution heat treatment is as follows: S41: first stage solid solution heat treatment of the hot forging treated ingot at 500-520 DEG C for 10-60 min; S42: second stage solid solution heat treatment of the ingot at 520-550 DEG C for 10-60 min; S43: third stage solid solution heat treatment of the ingot at 550-580 DEG C for 10-60 min, and then cool to room temperature.

[0018] Further, the cooling method is water cooling or water mist cooling.

[0019] Preferably, in the step S15, the artificial aging heat treatment temperature is 170-200 DEG C, and the time is 2-10 h.

[0020] Preferably, the interval time between the solid solution heat treatment and the artificial aging heat treatment is not more than 6 h.

[0021] The application also provides a high strength and toughness anti-fatigue aluminum alloy prepared by the above preparation method.

[0022] Preferably, the alloy deformation structure of the high strength and toughness anti-fatigue aluminum alloy is a mixed crystal structure of subgrain and recrystallization; in the mixed crystal structure, the proportion of the subgrain structure is greater than 60%, the size of the subgrain is less than 10.0 mu m, and the proportion of the recrystallization structure is 10-30%, and the grain size of the recrystallization structure is less than 20.0 mu m.

[0023] Compared with the prior art, the technical scheme of the application has the following advantages: The present application forms a core-shell structure dispersed phase in the alloy by the above-mentioned transition group elements Mn, Cr, Mo synergistic micro-alloying and regulating the Mn / (Cr+Mo) ratio, taking Cr and Mo as the shell and Al(FeMn)Si phase as the core, thereby greatly improving the thermal stability of the dispersed phase, reducing the average equivalent diameter of the dispersed phase to below 250.0 nm, and obtaining a dispersed phase in coherent or semi-coherent relationship with the matrix; by regulating the three-stage homogenization heat treatment, the number density of the dispersed phase in the aluminum alloy is significantly improved to 10 21 -10 22 m -3 ; the distribution uniformity of the dispersed phase is improved by regulating the hot forging and three-stage solid solution heat treatment process, the dispersed phase free zone (DFZ) is effectively reduced to within 2.00 μm, the sub-grain structure in the aluminum alloy is increased to 60% or more, the sub-grain size is regulated to within 10.0 μm, and the occurrence of recrystallization is effectively inhibited, the recrystallization ratio is controlled to be within 10%, and the recrystallization grain size is less than 20.0 μm.

[0024] The present application provides a processing method for optimizing the internal dispersed phase structure of high-strength fatigue-resistant 6XXX series aluminum alloy, improving its number density, reducing its average equivalent diameter and dispersed phase free zone (DFZ) width, and simultaneously having a mixed crystal structure characteristic, which innovatively controls the organizational characteristics (sub-grain and recrystallized structure) in the aluminum alloy by regulating the dispersed phase precipitation characteristics (phase structure, number density and average size), realizes efficient inhibition of the fatigue crack propagation rate of the 6XXX series aluminum alloy, and ensures high strength, high toughness and high fatigue resistance of the product.

[0025] The 6XXX series aluminum alloy with mixed crystal structure characteristics of coexistence of sub-grain and recrystallization has the characteristics of high strength, high toughness and high fatigue resistance, and the reasons are as follows: 1. The recrystallization degree of the mixed crystal alloy is low, the number of grains is relatively high, and the densities of low-angle grain boundaries (LAGBs) and high-angle grain boundaries (HAGBs) are relatively high, which increases the crack propagation resistance.

[0026] 2. The mixed crystal alloy has more grains with different Schmid factors, and the Schmid factor distribution range in the mixed crystal alloy is the widest, and when the crack passes through these grains, it will be obviously deflected, thereby forming a more tortuous propagation path.

[0027] 3. There are more sub-grain structures and recrystallized grains in the mixed crystal alloy. When the crack propagates, the sub-grain structure effectively improves the plastic deformation ability of the alloy, resulting in a more tortuous crack propagation path. At the same time, the recrystallized grains also deflect the crack propagation path. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 This is a schematic diagram of the distribution of the dispersed phase in the aluminum alloy of the present invention; wherein, (a) is Example 1 of the present invention, (b) is Comparative Example 1, (c) is Comparative Example 2, and (d) is Comparative Example 3.

[0029] Figure 2 The diagram shows the width of the non-precipitated dispersion zone (DFZ) in the aluminum alloy microstructure of the present invention; wherein, (a) is Example 1 of the present invention, (b) is Comparative Example 1, (c) is Comparative Example 2, and (d) is Comparative Example 3.

[0030] Figure 3 The images are scanning electron microscope images of the deformed microstructure of the aluminum alloy after solution heat treatment according to the present invention; wherein, (a) is Example 1 of the present invention, (b) is Comparative Example 1, (c) is Comparative Example 2, and (d) is Comparative Example 3. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0032] Example 1:

[0033] In this embodiment, the alloy chemical element composition and mass percentage of the high-strength, high-toughness, fatigue-resistant aluminum alloy material described in the invention are as follows: Mg: 0.90%, Si: 1.03%, Mn: 0.70%, Cu: 0.70%, Cr: 0.10%, Mo: 0.10%, Fe: 0.06%, Ti: 0.03%, other unavoidable impurities totaling 0.05%, with the balance being Al, and the Mn / (Cr+Mo) ratio being 3.50%.

[0034] The preparation method of this high-strength, high-toughness, fatigue-resistant aluminum alloy includes the following preparation steps: Step 1: Perform smelting and semi-continuous casting processes, as follows: 1) Prepare the ingredients according to the alloy composition; (2) Place pure Al and AlSi20 master alloy into a melting furnace, set the furnace temperature to 750 ℃, until all raw materials are completely melted; (3) Add AlMn10, AlMo5 and AlCr10 master alloys in sequence until completely melted, and hold the melt for 15 min. (4) When the melt temperature drops to 720 °C, add pure Cu and pure Mg in sequence; (5) The furnace temperature is raised to 740 °C for refining. High-purity argon gas is used to degas the high-temperature melt for 15 min. Then, slag removal is performed, and the melt is kept at the temperature for 15 min. (6) When the furnace temperature drops to 720 ℃, the melt is cast into the required ingot.

[0035] Step 2: Homogenization treatment. The ingot is subjected to the first homogenization treatment at 250 ℃ for 4 h, then the second homogenization treatment at 400 ℃ for 4 h, and finally the third homogenization treatment at 560 ℃ for 10 h. After that, it is cooled to 25 ℃ within 5 s. The heating rate is 3 ℃ / min and the cooling method is water cooling.

[0036] Step 3: Hot forging treatment. Hot forging is another determining factor in the formation and size of fine subgrains. In this embodiment, according to the hot forging treatment procedure, the hammer of the hot forging equipment is first preheated to 425 ℃, the hot forging temperature of the sample is 530 ℃, the preferred hot forging speed is 50 mm / s, the deformation is 70%, and immediately after hot forging, it is water-cooled to 25 ℃ within 5 seconds.

[0037] Step 4: Solution heat treatment. Perform the first stage of solution heat treatment at 515 ℃ for 45 min, then perform the second stage of solution heat treatment at 540 ℃ for 35 min, and finally perform the third stage of heat solution treatment at 560 ℃ for 20 min. The heating rate is 3 ℃ / min, and the cooling method is water cooling, cooling to 25 ℃ within 5 s.

[0038] Artificial aging heat treatment was performed by holding at 180 ℃ for 12 h, followed by water cooling to 25 ℃ within 5 s. The interval between solution treatment and aging heat treatment was 1 h.

[0039] Mechanical property testing: Tensile specimens were prepared according to GB / T 228-2021 standard. The tensile specimens were tested on a Shimadzu AGS-X universal testing machine in Japan at a tensile speed of 2 mm / min. The experimental data of tensile strength, yield strength and elongation were obtained.

[0040] Fatigue cycle test: Samples were prepared according to the test method of GB / T 3075-2021, and the fatigue test was carried out on an Instron 8801 fatigue testing machine. The number of cycles was recorded under the conditions of fatigue stress loads of 150 MPa and 160 MPa, frequency of 40 Hz, and stress ratio R = -1.

[0041] The statistical results of the dispersed phase, subgrain structure, and recrystallized structure are shown in Table 1, and the test results are shown in Table 2.

[0042] Comparative Example 1: The preparation method of the high-strength, high-toughness, fatigue-resistant aluminum alloy in this comparative example is basically the same as that in Example 1.

[0043] The only difference between Comparative Example 1 and Example 1 is that the chemical composition does not contain Cr and Mo elements, and AlMo5 and AlCr10 master alloys are not added. The chemical element composition and mass percentage are: Mg: 0.90%, Si: 1.03%, Mn: 0.70%, Cu: 0.70%, Fe: 0.06%, Ti: 0.03%, and the total amount of other unavoidable impurities is 0.05%, with the balance being Al.

[0044] Comparative Example 2: The preparation method of the high-strength, high-toughness, and fatigue-resistant aluminum alloy in this comparative example has the same chemical composition as in Example 1. The preparation method of the high-strength, high-toughness, and fatigue-resistant aluminum alloy includes the following preparation steps: Step 1: Melting and semi-continuous casting process.

[0045] Step 2: Homogenization treatment, holding at 570 ℃ for 10 h, heating rate of 3 ℃ / min, cooling method is water cooling, cooling to 25 ℃ within 5 s.

[0046] Step 3: Hot forging treatment. First, preheat the hammer of the hot forging equipment to 425 ℃. The preferred hot forging temperature for the sample is 530 ℃, the preferred hot forging speed is 50 mm / s, and the preferred deformation is 70%. After hot forging, immediately water cool it to 25 ℃ within 5 seconds.

[0047] Step 4: Solution heat treatment. The first stage of solution treatment is carried out at 515 ℃ for 45 min, followed by the second stage of solution treatment at 540 ℃ for 35 min, and finally the third stage of solution treatment at 560 ℃ for 20 min. The heating rate is 3 ℃ / min, and the cooling method is water cooling, cooling to 25 ℃ within 5 s. The sample is left to stand for 1 h before aging, the maximum aging temperature is 180 ℃, and the cooling method is water cooling, cooling to 25 ℃ within 5 s.

[0048] The test methods for the samples in Comparative Example 2 are the same as those in Example 1. The statistical results of the dispersed phase, subgrain structure, and recrystallized structure are shown in Table 1, and the test results are shown in Table 2.

[0049] Comparative Example 3: The high-strength, high-toughness, fatigue-resistant aluminum alloy and its preparation method described in this comparative example have the same chemical composition as in Example 1.

[0050] The preparation method of the high-strength, high-toughness, and fatigue-resistant aluminum alloy includes the following preparation steps: Step 1: Melting and semi-continuous casting process.

[0051] Step 2: Homogenization treatment. The first homogenization treatment is carried out at 250℃ for 4 hours, followed by the second homogenization treatment at 400℃ for 4 hours, and finally the third homogenization treatment at 560℃ for 10 hours. The heating rate is 3℃ / min, and the cooling method is water cooling, cooling to 25℃ within 5 seconds.

[0052] Step 3: Hot forging treatment. First, preheat the hammer of the hot forging equipment to 425 ℃. The preferred hot forging temperature for the sample is 530 ℃, the preferred hot forging speed is 50 mm / s, and the preferred deformation is 70%. After hot forging, immediately water cool it to 25 ℃ within 5 seconds.

[0053] Step 4: Perform solution treatment on the hot-forged sample, hold at 570 ℃ for 30 min, and cool with water to 25 ℃ within 5 s; the sample is left to stand for 1 h before aging, the maximum aging temperature is 180 ℃, and the sample is cooled with water to 25 ℃ within 5 s.

[0054] The test methods for the samples in Comparative Example 3 are the same as those in Example 1. The statistical results of the dispersed phase, subgrain structure, and recrystallized structure are shown in Table 1, and the test results are shown in Table 2.

[0055] Table 1. Statistical Analysis of Microstructure Characteristics of Alloys

[0056] Table 2 Test results of the samples

[0057] Effect evaluation To highlight the excellent strength, toughness, and fatigue resistance of the aluminum alloy prepared in this invention, the microstructures of the aluminum alloys in Example 1 and Comparative Examples 1, 2, and 3 were compared for easier understanding. Figure 1 , Figure 2 and Figure 3 This demonstrates that the microstructure of the aluminum alloy prepared by the present invention is superior to that of Comparative Example 1, Comparative Example 2 and Comparative Example 3.

[0058] Figure 1 (a) to (d) are schematic diagrams of the dispersed phase distribution in the alloys of Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3, respectively. The results show that the preparation method of the present invention obtained the highest number density of dispersed phases, which provides a higher pinning force for pinning subgrain structures and grain boundaries. The aluminum alloy prepared in Comparative Example 1 has the lowest number density of dispersed phases. The number density of dispersed phases inside the alloys prepared in Comparative Example 2 and Comparative Example 3 is improved, but still lower than that in Example 1.

[0059] Figure 2 Figures (a) to (d) are schematic diagrams showing the width distribution of the dispersion phase-free zone (DFZ) in the alloys of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3, respectively. The results show that the preparation method described in Example 1 of the present invention obtained the smallest width of the dispersion phase-free zone. The aluminum alloy prepared in Comparative Example 1 has the largest width of the dispersion phase-free zone. The width of the dispersion phase-free zone in the alloys prepared in Comparative Example 2 and Comparative Example 3 is reduced, but is still greater than that of the aluminum alloy prepared in Example 1. The smallest width of the dispersion phase-free zone in the aluminum alloy prepared in Example 1 provides a theoretical basis for improving the uniformity of dispersion phase distribution and improving the strength of the alloy.

[0060] Figure 3 Figures (a) to (d) are schematic diagrams of the deformation microstructure distribution of the alloys after solution heat treatment in Examples 1, Comparative Examples 1, 2, and 3, respectively. The results show that the aluminum alloys obtained by the preparation method of the present invention are mainly composed of recovery microstructure, with small angle grain boundaries (LAGBs) accounting for the highest proportion. The aluminum alloy prepared in Comparative Example 1 underwent the highest degree of recrystallization, with large angle grain boundaries (HAGBs) accounting for the highest proportion. The aluminum alloy prepared in Comparative Example 2 also underwent relatively severe recrystallization, with a high proportion of large angle grain boundaries and abnormally large grains. The aluminum alloy prepared in Comparative Example 3 also underwent a certain degree of recrystallization, with a high proportion of large angle grain boundaries. The highest proportion of small angle grain boundaries in the aluminum alloy prepared in Example 1 provides a theoretical basis for improving the toughness and fatigue strength of the alloy.

[0061] As shown in Table 1, the density of the dispersed phase in the alloy of Example 1 reaches 3.15 × 10⁻⁶. 21 m -3 The width of the dispersion-free zone (DFZ) is less than 2.00 μm, with spherical dispersed phase accounting for 38%. After hot forging and solution treatment, the subgrain structure accounts for 75%, and the recrystallization accounts for only 5%, with a recrystallized grain size of 18.0 μm. As shown in Table 2, the mechanical and fatigue properties of the 6XXX series aluminum alloy obtained by the heat treatment and hot forging method provided by this invention in Example 1 are superior to those of other comparative examples. This is because the microstructure of the sample in Example 1 after hot forging and solution heat treatment exhibits typical mixed-grain structure characteristics, mainly subgrain structure with recrystallized structure in some areas. Since the recrystallized area and the subgrain structure area form a "soft and hard alternation" microstructure, the soft area (recrystallized grains) deforms preferentially, while the hard area (subgrain) maintains strength. The synergistic effect of the two significantly improves the strength and elongation of the alloy. In addition, the presence of subgrain structure and recrystallized structure makes the path more prone to deflection, resulting in a more tortuous path, thereby improving the fatigue crack propagation resistance.

[0062] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a high-strength, high-toughness, fatigue-resistant aluminum alloy, characterized in that, Includes the following steps: S11: Aluminum, copper, magnesium, and a master alloy are smelted and semi-continuously cast to obtain an ingot; the ingot comprises the following elements by weight percentage: 0.6-1.4% Mg, 0.6-1.4% Si, 0.5-1% Mn, 0.3-0.8% Cu, 0.1-0.4% Cr, 0.1-0.3% Mo, Fe not more than 0.15%, Ti not more than 0.05%, other unavoidable impurities not more than 0.05%, and the balance being Al; wherein the sum of Cr and Mo is not more than 0.4%, and the mass ratio of Mn to the sum of Cr and Mo is 2-5:1; S12: The ingot is subjected to multi-stage homogenization heat treatment; after the multi-stage homogenization heat treatment, α-Al(Mn,Cr,Mo)Si dispersed phase is precipitated in the ingot; S13: The ingot after the multi-stage homogenization heat treatment is subjected to hot forging treatment; S14: Perform solution heat treatment on the hot-forged ingot; S15: The ingot after solution heat treatment is subjected to artificial aging heat treatment to obtain the high-strength, high-toughness, fatigue-resistant aluminum alloy.

2. The preparation method according to claim 1, characterized in that, The intermediate alloy is selected from AlSi20, AlMn10, AlMo5 and AlCr10.

3. The preparation method according to claim 1, characterized in that, In step S12, the precipitated α-Al(Mn,Cr,Mo)Si dispersed phase has a core-shell structure and a number density of 10. 21 -10 22 m -3 The average equivalent diameter is less than 250 nm, and the width of the non-precipitated region of the dispersed phase is less than 2 μm.

4. The preparation method according to claim 1, characterized in that, In step S12, the multi-stage homogenization heat treatment steps are as follows: S21: Hold the ingot at 380-420 ℃ for 2-6 h; S22: Hold the ingot at a temperature of 450-500 ℃ for 1-4 h; S23: Hold the ingot at 530-570 ℃ for 6-12 h and then cool it to room temperature; in steps S21-S23, the heating rate is 0.5-5 ℃ / min.

5. The preparation method according to claim 1, characterized in that, In step S13, the hot forging process is performed as follows: S31: Hold the ingot after multi-stage homogenization heat treatment at 450-530 ℃ for 0.5-2 h; S32: The ingot is hot-forged and then cooled to room temperature; the hot-forging speed is 10-50 mm / s and the deformation is 50-70%.

6. The preparation method according to claim 1, characterized in that, In step S14, the solution heat treatment process is as follows: S41: The hot-forged ingot is subjected to first-stage solution heat treatment at 500-520 ℃ for 10-60 min; S42: The ingot is subjected to a second-stage solution heat treatment at 520-550 ℃ for 10-60 min; S43: The ingot is subjected to a third-stage solution heat treatment at 550-580 ℃ for 10-60 min and then cooled to room temperature.

7. The preparation method according to any one of claims 4-6, characterized in that, The cooling method is water cooling or water mist cooling.

8. The preparation method according to claim 1, characterized in that, In step S15, the temperature of the artificial aging heat treatment is 170-200 ℃, the time is 2-10 h, and the interval between the solution heat treatment and the artificial aging heat treatment does not exceed 6 h.

9. A high-strength, high-toughness, fatigue-resistant aluminum alloy prepared by the preparation method according to any one of claims 1-8.

10. The high-strength, high-toughness, fatigue-resistant aluminum alloy as described in claim 9, characterized in that, The high-strength, high-toughness, and fatigue-resistant aluminum alloy has a mixed-grain structure in its deformed structure. In the mixed-grain structure, the proportion of subgrain structure is greater than 60%, the size of the subgrain is less than 10 μm, the proportion of recrystallized structure is 10-30%, and the grain size of the recrystallized structure is less than 20 μm.

Images