High-toughness fatigue-resistant aluminum alloy and method for manufacturing the same

Abstract

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. The alloy has the following components in percentage by mass: Mg: 0.6-1.4%, Si: 0.6-1.4%, Mn: 0.5-1%, Cu: 0.3-0.8%, Cr: 0.1-0.4%, Mo: 0.1-0.3%, Fe: less than or equal to 0.15%, Ti: less than or equal to 0.05%, total amount of other impurities: less than or equal to 0.05%, and the balance being Al. The ratio of Mn / (Cr+Mo) in the alloy is 2-5, and Cr+Mo is less than or equal to 0.4. The aluminum alloy is subjected to element Mn, Cr and Mo synergistic micro-alloying and three-stage homogenization treatment, so as to precipitate high-density 'core-shell' structure dispersed phase, effectively improving the deformation organization regulation effect; the aluminum alloy is subjected to hot forging and multi-stage solid solution treatment, so as to obtain mixed crystal organization coexisting with subgrain and recrystallization, significantly reducing the fatigue crack propagation rate, and synchronously improving the strength and toughness and the anti-fatigue performance.

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 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 easy dynamic recovery during thermal mechanical processing, and easy 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 alloy preparation is the key to realizing high strength, high toughness and high anti-fatigue.

[0007] Therefore, it has important practical significance and important 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, having the mixed crystal organization 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:

[0009] The present application provides a preparation method of high-strength and high-toughness anti-fatigue aluminum alloy, comprising the following steps:

[0010] 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%, total amount of 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;

[0011] 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;

[0012] S13: Hot forging treatment of the ingot after the multi-stage homogenization heat treatment;

[0013] S14: Solid solution heat treatment of the ingot after the hot forging;

[0014] 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.

[0015] 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 organization, have the mixed crystal organization 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.

[0016] Preferably, the intermediate alloy is selected from AlSi20, AlMn10, AlMo5 and AlCr10.

[0017] Preferably, the smelting and semi-continuous casting steps are as follows:

[0018] (1) After batching, Al and AlSi20 are heated to 750-760 ℃ for melting;

[0019] (2) AlMn10, AlMo5 and AlCr10 are added to the melted material, and the temperature is kept at 750-760 ℃ for 10-20 min;

[0020] (3) The melt is cooled to 720 ℃, pure Cu and pure Mg are added, and the temperature is raised to 730-750 ℃ under inert atmosphere for refining for 10-20 min;

[0021] (4) The melt is subjected to slagging treatment and kept for 12-18 min;

[0022] (5) The temperature is lowered to 720-730 ℃, and the ingot is cast.

[0023] Specifically, the smelting and semi-continuous casting steps are as follows:

[0024] (1) The alloy components are batched;

[0025] (2) Pure Al and AlSi20 intermediate alloy are put into a smelting furnace, and the furnace temperature is set to 750-760 ℃ until all the raw materials are completely melted;

[0026] (3) AlMn10, AlMo5 and AlCr10 intermediate alloys are sequentially added until completely melted, and the melt is kept for 10-20 min;

[0027] (4) When the melt temperature drops to 720 ℃, pure Cu and pure Mg are sequentially added;

[0028] (5) The furnace temperature is raised to 730-750 ℃ for refining, high-purity argon is used to degas the high-temperature melt, the degassing time is 10-20 min, then slagging treatment is performed, and the melt is kept for 12-18 min;

[0029] (6) When the furnace temperature drops to 720-730 ℃, the melt is cast into the required alloy ingot.

[0030] Preferably, in the step S12, the precipitated α-Al(Mn, Cr, Mo)Si dispersed phase is in a 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.

[0031] Preferably, in the step S12, the multi-stage homogenization heat treatment is as follows:

[0032] S21: holding the ingot at a temperature of 380-420 ℃ for 2-6 h;

[0033] S22: holding the ingot at a temperature of 450-500 ℃ for 1-4 h;

[0034] 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.

[0035] Preferably, in the step S13, the hot forging treatment is as follows:

[0036] S31: preheating the hammer head of the hot forging equipment to 400-425 ℃, and the heating mode of the hammer head of the hot forging equipment is resistance heating; the ingot after the multi-stage homogenization heat treatment is held at 450-530 ℃ for 0.5-2 h;

[0037] S32: cooling the ingot after the hot forging to room temperature; the speed of the hot forging is 10-50 mm / s, and the deformation amount is 50-70%.

[0038] Further, the time from the hot forging to the cooling is less than 5 s.

[0039] Preferably, in the step S14, the solid solution heat treatment is as follows:

[0040] S41: first-stage solid solution heat treatment of the ingot after the hot forging treatment at 500-520 ℃ for 10-60 min;

[0041] S42: second-stage solid solution heat treatment of the ingot at 520-550 ℃ for 10-60 min;

[0042] S43: third-stage solid solution heat treatment of the ingot at 550-580 ℃ for 10-60 min and then cooling to room temperature.

[0043] Further, the cooling method is water cooling or water mist cooling.

[0044] Preferably, in the step S15, the artificial aging heat treatment is at a temperature of 170-200 ℃ for 2-10 h.

[0045] Preferably, the interval between the solid solution heat treatment and the artificial aging heat treatment is not more than 6 h.

[0046] The application further provides the high-strength and high-toughness aluminum alloy prepared by the preparation method.

[0047] Preferably, the alloy deformation structure of the high-strength and high-toughness aluminum alloy is a mixed crystal structure in which subgrains and recrystallization coexist; 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 microns, and the proportion of the recrystallization structure is 10-30%, and the grain size of the recrystallization structure is less than 20.0 microns.

[0048] Compared with the prior art, the technical scheme of the application has the following advantages:

[0049] The application forms a core-shell structure dispersed phase in the alloy by the transition group elements Mn, Cr and Mo, 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; 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 the regulated hot forging and three-stage solid solution heat treatment process, the dispersed phase free zone (DFZ) is effectively reduced to within 2.00 microns, the proportion of subgrain structure in the aluminum alloy is increased to 60% or more, the subgrain size is regulated to within 10.0 microns, and the occurrence of recrystallization is effectively inhibited, the proportion of recrystallization is controlled to within 10%, and the recrystallization grain size is less than 20.0 microns.

[0050] The application provides a processing method for optimizing the internal dispersed phase structure of high-strength and fatigue-resistant 6XXX series aluminum alloy, improving the number density, reducing the average equivalent diameter and the width of the dispersed phase free zone (DFZ), and simultaneously having the characteristics of mixed crystal structure, which innovatively controls the structure characteristics (subgrain and recrystallization 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 guarantees the high strength, high toughness and high fatigue resistance of the product.

[0051] The 6XXX series aluminum alloy with the characteristics of mixed crystal structure in which subgrains and recrystallization coexist has the characteristics of high strength, high toughness and high fatigue resistance, and the reasons are as follows:

[0052] 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, thereby increasing the crack propagation resistance.

[0053] 2. Mixed crystal alloys have more grains with different Schmid factors, and the Schmid factor distribution is the widest in mixed crystal alloys. When cracks pass through these grains, they will be significantly deflected, thus forming a more tortuous propagation path.

[0054] 3. Mixed-grain alloys contain a significant amount of subgrained structures and recrystallized grains. During crack propagation, the subgrained structures effectively improve the alloy's plastic deformation capacity, leading to a more tortuous crack propagation path. Simultaneously, the recrystallized grains also deflect the crack propagation path. Attached Figure Description

[0055] 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.

[0056] 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.

[0057] 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

[0058] 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.

[0059] Example 1:

[0060] 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%.

[0061] The preparation method of this high-strength, high-toughness, fatigue-resistant aluminum alloy includes the following preparation steps:

[0062] Step 1: Perform smelting and semi-continuous casting processes, as follows:

[0063] 1) Prepare the ingredients according to the alloy composition;

[0064] (2) Put pure Al and AlSi20 intermediate alloy into the smelting furnace, set the furnace temperature to 750 ℃, until all the raw materials are completely melted;

[0065] (3) Add AlMn10, AlMo5 and AlCr10 intermediate alloy in turn until completely melted, and the melt is kept for 15 min;

[0066] (4) When the melt temperature drops to 720 ℃, add pure Cu and pure Mg in turn;

[0067] (5) Increase the furnace temperature to 740 ℃ for refining, use high-purity argon to degas the high-temperature melt, degassing time is 15 min, then perform slagging treatment, and then keep the melt for 15 min;

[0068] (6) When the furnace temperature drops to 720 ℃, cast the melt into the required ingot.

[0069] Step two: homogenization treatment, the ingot is subjected to first-stage homogenization treatment at 250 ℃ for 4 h, then second-stage homogenization treatment at 400 ℃ for 4 h, and finally third-stage homogenization treatment at 560 ℃ for 10 h, and then cooled to 25 ℃ within 5 s, the heating rate is 3 ℃ / min, and the cooling method is water cooling.

[0070] Step three: hot forging treatment, hot forging processing is another determining factor for the formation and size of fine subgrains. According to the hot forging treatment system of this embodiment, first, the hammer head of the hot forging equipment is preheated to 425 ℃, the hot forging temperature of the sample is 530 ℃, the preferred hot forging speed is 50 mm / s, the deformation amount is 70 %, and after hot forging, the sample is immediately water-cooled to 25 ℃ within 5 s.

[0071] Step four: solid solution heat treatment, first-stage solid solution heat treatment at 515 ℃ for 45 min, second-stage solid solution heat treatment at 540 ℃ for 35 min, and finally third-stage solid solution heat treatment at 560 ℃ for 20 min, the heating rate is 3 ℃ / min, the cooling method is water cooling, and the sample is cooled to 25 ℃ within 5 s.

[0072] Artificial aging heat treatment, aging at 180 ℃ for 12 h, the cooling method is water cooling, and the sample is cooled to 25 ℃ within 5 s, the interval time between solid solution and aging heat treatment is 1 h.

[0073] Mechanical property test: according to GB / T 228-2021 standard, tensile specimens are prepared, and the tensile specimens are tested on a Japanese Shimadzu AGS-X universal material testing machine, the tensile speed is 2 mm / min, and the tensile strength, yield strength and elongation experimental data are obtained.

[0074] Fatigue cycle number test: The sample was 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 fatigue stress load was 150 MPa and 160 MPa, the frequency was 40 Hz, and the stress ratio R = -1. The cycle number was recorded under the condition of.

[0075] The statistical results of the dispersion phase and the subgrain structure and recrystallized structure are shown in Table 1, and the test results are shown in Table 2.

[0076] Comparative Example 1

[0077] The preparation method of the high-strength and high-toughness fatigue-resistant aluminum alloy in the present comparative example is basically the same as that of Example 1.

[0078] The difference between the preparation method of Comparative Example 1 and Example 1 is that the chemical composition does not contain Cr and Mo elements, and no AlMo5 and AlCr10 intermediate alloy is 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%, and the balance is Al.

[0079] Comparative Example 2

[0080] The preparation method of the high-strength and high-toughness fatigue-resistant aluminum alloy in the present comparative example is basically the same as that of Example 1.

[0081] Step one: melting and semi-continuous casting treatment.

[0082] Step two: homogenization treatment, heat preservation at 570 ℃ for 10 h, heating rate is 3 ℃ / min, cooling method is water cooling, cooling to 25 ℃ within 5 s.

[0083] Step three: hot forging treatment, first preheat the hammer head of the hot forging equipment to 425 ℃, the preferred hot forging temperature of the sample is 530 ℃, the preferred hot forging speed is 50 mm / s, the preferred deformation is 70%, and the hot forging is immediately followed by water cooling, cooling to 25 ℃ within 5 s.

[0084] Step four: solid solution heat treatment, first stage solid solution treatment at 515 ℃ for 45 min, second stage solid solution treatment at 540 ℃ for 35 min, and third stage solid solution treatment at 560 ℃ for 20 min, the heating rate is 3 ℃ / min, and the cooling mode is water cooling, cooled to 25 ℃ within 5 s; the sample storage time before aging is 1 h, the maximum aging temperature is 180 ℃, and the cooling mode is water cooling, cooled to 25 ℃ within 5 s.

[0085] The test method of the sample in Comparative Example 2 is the same as that in Example 1, the statistical results of the dispersion phase and the subgrain and recrystallization structure are shown in Table 1, and the test results are shown in Table 2.

[0086] Comparative Example 3:

[0087] The high-strength and high-toughness anti-fatigue aluminum alloy and the preparation method thereof in the present comparative example have the same chemical composition as that in Example 1.

[0088] The preparation method of the high-strength and high-toughness anti-fatigue aluminum alloy comprises the following preparation steps:

[0089] Step one: melting and semi-continuous casting treatment.

[0090] Step two: homogenization treatment, first stage homogenization treatment at 250 ℃ for 4 h, second stage homogenization treatment at 400 ℃ for 4 h, and third stage homogenization treatment at 560 ℃ for 10 h, the heating rate is 3 ℃ / min, and the cooling mode is water cooling, cooled to 25 ℃ within 5 s.

[0091] Step three: hot forging treatment, first preheat the hammer head of the hot forging equipment to 425 ℃, the preferred hot forging temperature of the sample is 530 ℃, the preferred hot forging speed is 50 mm / s, the preferred deformation amount is 70 %, and immediately perform water cooling after hot forging, cooled to 25 ℃ within 5 s.

[0092] Step four: solid solution treatment on the hot forged sample, heat preservation at 570 ℃ for 30 min, the cooling mode is water cooling, cooled to 25 ℃ within 5 s; the sample storage time before aging is 1 h, the maximum aging temperature is 180 ℃, and the cooling mode is water cooling, cooled to 25 ℃ within 5 s.

[0093] The test method of the sample in Comparative Example 3 is the same as that in Example 1, the statistical results of the dispersion phase and the subgrain and recrystallization structure are shown in Table 1, and the test results are shown in Table 2.

[0094] Table 1 Analysis of microstructure characteristics of alloys

[0095]

[0096] Table 2 Test results of samples

[0097]

[0098] Effect evaluation

[0099] In order to highlight the good strength and toughness and excellent fatigue resistance of the aluminum alloy prepared by the present application, the microstructures of the aluminum alloys in Example 1 and Comparative Examples 1, 2 and 3 are compared, so as to facilitate understanding and Figure 1 、 Figure 2 and Figure 3 It is shown that the microstructure of the aluminum alloy prepared by the present application is superior to those of Comparative Examples 1, 2 and 3.

[0100] Figure 1 (a) to (d) of FIG. 1 are schematic diagrams of the distribution of the dispersed phase of the alloys in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3, respectively, and the results show that the highest number density of dispersed phase is obtained by the preparation method of the present application, which provides higher pinning force (Zener force) for the pinning of subgrain structure and grain boundary, the number density of dispersed phase of the aluminum alloy prepared in Comparative Example 1 is the lowest, and the number density of dispersed phase in the alloys prepared in Comparative Examples 2 and 3 is improved, but still lower than that in Example 1.

[0101] Figure 2 (a) to (d) of FIG. 2 are schematic diagrams of the width distribution of the dispersed phase free zone (DFZ) of the alloys in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3, respectively, and the results show that the smallest width of the dispersed phase free zone is obtained by the preparation method of Example 1, the width of the dispersed phase free zone of the aluminum alloy prepared in Comparative Example 1 is the largest, the width of the dispersed phase free zone of the alloys prepared in Comparative Examples 2 and 3 is reduced, but still greater than that of the aluminum alloy prepared in Example 1, and the smallest width of the dispersed phase free zone of the aluminum alloy prepared in Example 1 provides a theoretical basis for improving the uniformity of dispersed phase distribution and improving the strength of the alloy.

[0102] Figure 3 (a) to (d) of FIG. 3 are schematic diagrams of the distribution of the deformed structure of the alloys after solid solution heat treatment in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3, respectively, and the results show that the aluminum alloy prepared by the preparation method of the present application is mainly recovered structure, and the proportion of low-angle grain boundaries (LAGBs) is the highest, the highest degree of recrystallization occurs in the aluminum alloy prepared in Comparative Example 1, and the proportion of high-angle grain boundaries (HAGBs) is the highest, the aluminum alloy prepared in Comparative Example 2 also undergoes relatively serious recrystallization, and the proportion of high-angle grain boundaries is high, and there are abnormally grown grains, the aluminum alloy prepared in Comparative Example 3 also undergoes a certain degree of recrystallization, and the proportion of high-angle grain boundaries is high, and the highest proportion of low-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.

[0103] As shown in Table 1, the density of the dispersed phase in the alloy in Example 1 reaches 3.15 x 10 21 m -3 The width of the dispersed phase free zone (DFZ) is less than 2.00 μm, the proportion of the spherical dispersed phase reaches 38%, the proportion of the subgrain structure after hot forging and solid solution treatment reaches 75%, the proportion of recrystallization is only 5%, and the size of the recrystallization grain is 18.0 μm. As shown in Table 2, the mechanical properties and fatigue properties of the 6XXX series aluminum alloy obtained by the heat treatment and hot forging method in Example 1 are better than those of the other comparative examples. This is because the sample in Example 1 presents a typical mixed crystal structure after hot forging and solid solution heat treatment, in which the subgrain structure is mainly present, and the recrystallization structure exists in some areas. Because the recrystallization region and the subgrain structure region form a "soft and hard alternating" microstructure, the soft region (recrystallization grain) deforms preferentially, and the hard region (subgrain) maintains the strength, and the synergistic effect of the two significantly improves the strength and elongation of the alloy. In addition, the existence of the subgrain structure and the recrystallization structure makes the path easy to deflect, resulting in a more tortuous path, and thus improving the fatigue crack propagation resistance.

[0104] Obviously, the above examples are only examples for clearly illustrating, and are not intended to limit the embodiments. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, all the embodiments do not need to be exhausted, and the obvious changes or variations derived therefrom are still within the protection scope of the present application.

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 intermediate alloys 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% 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, tough, and fatigue-resistant aluminum alloy. 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. 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; 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.

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 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%.

5. The preparation method according to claim 1 or 4, characterized in that, The cooling method is water cooling or water mist cooling.

6. A high-strength, high-toughness, fatigue-resistant aluminum alloy prepared by the preparation method according to any one of claims 1-5.

7. The high-strength, high-toughness, fatigue-resistant aluminum alloy as described in claim 6, 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.

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