A method for producing an aluminum alloy material having high strength and low fatigue crack growth rate

Abstract

The application provides a high-strength low-fatigue crack propagation rate aluminum alloy material preparation method, which comprises the following steps: mixing aluminum alloy powders with different particle sizes, hot isostatic pressing, plastic forming, and then sequentially performing solid solution treatment, cold deformation treatment and low-temperature aging treatment. The material preparation and processing method is simple and reasonable in process, the strength of the aluminum alloy material is improved by introducing a heterogeneous structure of coarse-fine grains and a refined precipitated phase organization; meanwhile, a strain gradient is formed near the interface of the coarse-fine grain area after the treatment, which can induce a heterogeneous strengthening effect, further realizing the strengthening effect and crack passivation effect, so that the strength and the anti-fatigue crack propagation ability are simultaneously improved.

Description

Technical Field

[0001] The present invention relates to a method for preparing an aluminum alloy material, and in particular to a microstructure design and preparation method capable of simultaneously improving the strength and fatigue crack propagation resistance of the aluminum alloy material, belonging to the technical field of aluminum alloy materials. Background Art

[0002] Aluminum alloys, with their advantages of light weight, high strength, damage resistance, and corrosion resistance, are the most commonly used lightweight structural materials. Deformed aluminum alloys, in particular, are widely used in the aviation sector. The rapid development of the aviation industry has placed higher demands on high-performance aluminum alloys. Improving the strength of aluminum alloys can further effectively achieve lightweight structures, while reducing the fatigue crack growth rate of aluminum alloys can improve the safety and durability of aviation components. Therefore, the development of aluminum alloys with high strength and low fatigue crack growth rate is of great practical significance for the development and upgrading of high-performance aviation structural materials.

[0003] Traditional strengthening strategies for aluminum alloys include grain refinement, dispersion strengthening, solid solution strengthening, and dislocation strengthening. However, for current deformed aluminum alloys, such as Al-Cu and Al-Zn series, conventional preparation, processing, and heat treatment techniques have shown limited strength gains. While large deformation processes can significantly increase strength, the complex process makes it difficult to produce large-scale aluminum alloy components. More importantly, these traditional strengthening strategies inevitably lead to increased fatigue crack growth rates, which is detrimental to the damage tolerance design requirements of aviation components. For example, grain refinement, increased dislocation density, and the introduction of a high volume fraction of dispersed particles all reduce the size of the plastic zone at the fatigue crack tip, significantly reducing the blunting effect of the deformation zone at the fatigue crack tip. Furthermore, grain refinement weakens the crack path deflection and closure effects, leading to an increase in fatigue crack growth rate. Coarser grains, on the other hand, improve crack blunting and closure capabilities but at the expense of strength.

[0004] It can be seen from this that there is an inverted relationship between the strength and fatigue crack growth resistance of aluminum alloys. How to improve the strength while reducing the fatigue crack growth rate is crucial to improving the comprehensive mechanical properties. It is urgent to design a new aluminum alloy microstructure configuration and optimize the precipitation phase characteristics to simultaneously achieve increased static load strength and reduced fatigue crack growth rate. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem that it is difficult to achieve simultaneous improvement of the strength and fatigue crack growth resistance of aluminum alloys in the existing technology. In view of the problem that the increase in strength of deformed aluminum alloys leads to an increase in fatigue crack growth rate or a decrease in fatigue crack growth rate leads to a decrease in strength, a technical method with industrial production conditions is provided to simultaneously improve the strength and fatigue crack growth resistance of aluminum alloys.

[0006] The present invention provides a method for preparing a high-strength and low-fatigue crack growth rate aluminum alloy material, comprising the following technical solutions: aluminum alloy powder is proportioned according to a two-level particle size distribution, and then powder mixing and hot isostatic pressing treatment, homogenization annealing treatment and plastic processing forming, solid solution treatment and cold deformation treatment, and low-temperature aging treatment are sequentially performed.

[0007] Specifically, the method for preparing the high-strength and low-fatigue crack growth rate aluminum alloy material of the present invention comprises the following steps:

[0008] (1) Two-stage particle size ratio: Screening two types of aluminum alloy powders with different particle size distributions, the first stage is fine aluminum alloy powder with an average particle size of 10-60 microns; the second stage is coarse aluminum alloy powder with an average particle size of 50-600 microns; wherein the fine aluminum alloy powder accounts for 60%-80% by weight;

[0009] (2) Powder mixing, vacuum degassing and hot isostatic pressing: After the fine aluminum alloy powder and the coarse aluminum alloy powder are fully mixed, vacuum degassing and hot isostatic pressing are performed to obtain an aluminum alloy ingot with a density of ≥99.5%;

[0010] (3) homogenization annealing and plastic forming: the aluminum alloy ingot is subjected to homogenization annealing, air-cooled, and then plastic formed to obtain a heterogeneous aluminum alloy material having a coarse-fine grain distribution;

[0011] (4) solution treatment and cold deformation treatment: the heterogeneous structure aluminum alloy material having a coarse-fine grain distribution is subjected to solution treatment, wherein the solution treatment includes heating, holding and water quenching steps; cold deformation treatment is immediately performed after the solution treatment, with a deformation amount of 3% to 30%, and the interval between the solution treatment and the end of the cold deformation treatment is less than or equal to 1 hour; and the deformed heterogeneous structure aluminum alloy material is obtained;

[0012] (5) Aging treatment: The deformed heterogeneous aluminum alloy material is subjected to aging treatment.

[0013] Preferably, the coarse and fine aluminum alloy powders are obtained by atomizing and then screening.

[0014] Preferably, the particle morphologies of the coarse aluminum alloy powder and the fine aluminum alloy powder are both approximately spherical, that is, the average aspect ratios of the coarse and fine aluminum alloy powders are both approximately 1, and the particle size distributions are both approximately normal distributions.

[0015] Preferably, the ratio of the average particle size of the coarse aluminum alloy powder to the average particle size of the fine aluminum alloy powder is 5-10.

[0016] Preferably, the vacuum degassing and hot isostatic pressing treatment to obtain an aluminum alloy ingot with a density ≥99.5% is as follows: the two powders after being fully mixed are first coated with a metal sheath, the heating temperature is 450-550°C, the vacuum degree inside the metal sheath is greater than or equal to 0.1Pa, and then hot isostatic pressing is performed with a pressure greater than or equal to 100MPa, a hot pressing temperature of 450-550°C, and a holding time of 2-8h. Subsequently, the heat preservation is continued for 12-24h under no external pressure for homogenization treatment, and finally air cooling is performed. The density of the obtained aluminum alloy ingot is ≥99.5%.

[0017] Preferably, the homogenization annealing treatment parameters in step (3) are: 450-500° C., and a holding time of 6-12 h.

[0018] Preferably, the plastic forming method in step (3) is hot rolling or hot extrusion, wherein the hot rolling is: the rolling starting temperature is 420°C, and when the total thickness deformation is 98% or greater than 98%, annealing is performed, the annealing temperature is 400°C, and the temperature is kept for 0.5h. After air cooling, cold rolling is performed, and aluminum alloy thin plates are formed through multiple rolling processes, and the total thickness deformation of cold rolling is greater than or equal to 60%. No annealing is performed during the cold rolling process; the hot extrusion is: the extrusion temperature is 420°C, and the plate is extruded to the target thickness.

[0019] Preferably, in step (4), the solution treatment is a single-stage solution treatment or a double-stage solution treatment. The single-stage solution treatment is as follows: heating to 450-550°C, holding for 45-60 minutes, followed by rapid water quenching, with a transfer time of less than or equal to 15 seconds; the double-stage solution treatment is as follows: heating to 470°C, holding for 30 minutes, then holding at 505°C for 30 minutes, followed by rapid water quenching, with a transfer time of less than or equal to 15 seconds.

[0020] Preferably, the interval between the end of the cold deformation treatment and the end of the solution treatment in step (4) is less than or equal to 30 minutes.

[0021] Preferably, in step (4), the cold deformation treatment is rolling or stretching, and the deformation temperature range is -50°C to 50°C.

[0022] Preferably, in step (5), the aging treatment is single-stage aging or two-stage aging. The single-stage aging treatment is 80-120° C. for 48-720 h; the two-stage aging treatment is 120-195° C. for 10-30 minutes and then 50-100° C. for 48-720 h.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention provides a method for preparing a high-strength, low fatigue crack growth rate aluminum alloy material. The process is simple and easy to operate. The powder making, hot isostatic pressing, plastic forming, and heat treatment involved all meet industrial production conditions, and can realize the preparation and processing of high-strength, low fatigue crack growth rate aluminum alloy materials; through plastic processing and forming, the required materials such as plates can be formed.

[0025] The present invention provides a method for preparing a high-strength and low fatigue crack growth rate aluminum alloy material. Fine aluminum alloy powder can form a fine-grained structure with a low dislocation density, and coarse powder can form a coarse-grained structure with a higher dislocation density, thereby realizing a heterogeneous grain microstructure design, wherein the fine-grained structure can improve the strength, and the coarse-grained structure can reduce the fatigue crack growth rate. Combined with an aging treatment process to refine the precipitated phase and control the dislocation density, a strain gradient is formed near the interface of the coarse-fine grain region, and a heterogeneous strengthening effect can be induced, thereby ultimately improving the strength of the aluminum alloy material while making it have a lower fatigue crack growth rate. DETAILED DESCRIPTION

[0026] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0027] Example 1

[0028] (1) Pure Al was added to a crucible and melted at 780°C. Al-Cu, Al-Mn master alloy, and pure Mg ingot were added in the order of Al-4.2Cu-1.8Mg-0.5Mn (mass fraction, %). The slag on the surface of the melt was removed after sufficient melting and stirring. The melt was allowed to stand for 15 minutes and then flowed out through a ceramic flow tube. The melt was then broken into droplets using a gas atomization method (high-pressure N2, pressure 10 MPa, flow rate 600 m / s). The droplets solidified to form spherical aluminum alloy powder. Fine aluminum alloy powder and coarse aluminum alloy powder were screened out. The average particle size of the fine aluminum alloy powder was 10 μm, and the average particle size of the coarse aluminum alloy powder was 50 μm. The average aspect ratio of the coarse and fine aluminum alloy powders was approximately 1, and the particle size distribution was approximately normal.

[0029] (2) The fine aluminum alloy powder is mixed with the coarse aluminum alloy powder with a mass fraction of 80% and the coarse aluminum alloy powder with a mass fraction of 20%. After the two alloy powders are fully mixed by mechanical mixing, they are first coated with a metal sheath, heated to a temperature of 550°C, and the vacuum degree inside the metal sheath is 0.1Pa. Then, hot isostatic pressing is performed with a pressure of 100MPa, a hot pressing temperature of 550°C, and a holding time of 8h. Then, the heat is continued for 12h without external pressure for homogenization treatment, and finally air cooling is performed. The density of the obtained aluminum alloy ingot is ~99.8%.

[0030] (3) The aluminum alloy ingot is then subjected to homogenization annealing at 500°C for 6 hours, and then air-cooled. The aluminum alloy ingot after homogenization annealing is hot-rolled at a starting temperature of 420°C to a thickness of 6 mm, which is 2% of the thickness before hot rolling. It is then annealed at 400°C for 0.5 hours. After air cooling, it is cold-rolled. After 15 passes, a 2 mm thick aluminum alloy sheet is obtained, with a cold-rolling thickness deformation of 67%. No annealing is performed during the cold rolling process.

[0031] (4) The plate is then solution treated, with the solution treatment process being 550°C for 45 min, followed by rapid water quenching, with a transfer time of less than 15 s; after solution treatment, it is transferred to the rolling mill within 30 min, cold rolled at -50°C, and the deformation is 3%.

[0032] (5) Finally, the plate is subjected to a single-stage aging treatment with the following process parameters: 80°C for 720 hours.

[0033] Room temperature mechanical property tests along the rolling direction show that the yield strength of Al-4.2Cu-1.8Mg-0.5Mn aluminum alloy plate is 460MPa, the tensile strength is 620MPa, and the elongation is 18%; the stress intensity factor range ΔK is 20MPa.m 0.5 The fatigue crack growth rate is 4×10 -4 mm / cycle.

[0034] Example 2

[0035] The same points as Example 1 are not repeated here, except that the mass fraction of the fine aluminum alloy powder is 60%; the mass fraction of the coarse aluminum alloy powder is 40%.

[0036] Room temperature mechanical property tests along the rolling direction show that the yield strength of Al-4.2Cu-1.8Mg-0.5Mn aluminum alloy plate is 445MPa, the tensile strength is 615MPa, the elongation is 20%; the stress intensity factor range ΔK is 20MPa.m 0.5 When the fatigue crack growth rate is 3×10 -4mm / cycle.

[0037] Example 3

[0038] The similarities with Example 1 are not repeated here. The differences are as follows: the atomization process parameters are adjusted (pressure 8 MPa, flow rate 300 m / s), and a fine alloy powder with an average particle size of 60 microns and a coarse aluminum alloy powder with an average particle size of 600 microns are obtained by screening; in step (4), the process for cold deformation treatment of the plate is: the deformation amount of cold rolling at 50°C is 30%; in step (5), the aging treatment is a two-stage aging treatment, and its process parameters are insulation at 195°C for 10 minutes and then insulation at 100°C for 48 hours.

[0039] Room temperature mechanical property tests along the rolling direction show that the yield strength of Al-4.2Cu-1.8Mg-0.5Mn aluminum alloy plate is 440MPa, the tensile strength is 610MPa, and the elongation is 21%; the stress intensity factor range ΔK is 20MPa.m 0.5 When the fatigue crack growth rate is 3.5×10 -4 mm / cycle.

[0040] Example 4

[0041] (1) Al-Zn-Mg-Cu alloy powder was used as raw material, and its specific alloy composition was Al-6.2Zn-2.3Mg-2.3Cu-0.1Zr (mass fraction, %). The same method as Example 1 was adopted, except that the atomization process parameters were adjusted (pressure 9 MPa, flow rate 500 m / s), and fine aluminum alloy powder with an average particle size of 30 μm and coarse aluminum alloy powder with an average particle size of 200 μm were prepared by sieving. The average aspect ratio of the coarse and fine aluminum alloy powders was approximately 1, and the particle size distribution was approximately normal.

[0042] (2) After the two alloy powders were fully mixed by mechanical mixing in a ratio of 60% by mass of fine aluminum alloy powder and 40% by mass of coarse aluminum alloy powder, they were first coated with a metal sheath, heated to 450°C, and the vacuum degree inside the metal sheath was 0.1 Pa. They were then hot isostatically pressed at a pressure of 100 MPa, a hot pressing temperature of 450°C, and a holding time of 2 h. They were then kept warm for 24 h without external pressure for homogenization treatment, and finally air-cooled. The density of the resulting aluminum alloy ingot was ~99.8%.

[0043] (3) The aluminum alloy ingot after hot isostatic pressing is then subjected to homogenization annealing at a temperature of 450°C for 12 hours, and then taken out for air cooling. The aluminum alloy ingot after homogenization annealing is then hot extruded at an extrusion temperature of 420°C and then extruded into a 5 mm thick plate.

[0044] (4) The plate is then solution treated at 450°C for 60 min, followed by rapid water quenching with a transfer time of less than 15 s; the plate is transferred to a stretching machine within 1 h and stretched at 25°C by 5%.

[0045] (5) Finally, the plate was subjected to a single-stage aging treatment with the process parameters of 120 °C for 48 h.

[0046] Room temperature mechanical property tests along the extrusion direction show that the yield strength of the Al-6.2Zn-2.3Mg-2.3Cu-0.1Zr aluminum alloy sheet is 720MPa, the tensile strength is 760MPa, and the elongation is 12%; the stress intensity factor range ΔK is 20MPa.m 0.5 When the fatigue crack growth rate is 8×10 -4 mm / cycle.

[0047] Example 5

[0048] The similarities with Example 4 are not repeated here. The differences are: adjusting the atomization process parameters (pressure 9 MPa, flow rate 500 m / s), and obtaining fine aluminum alloy powder with an average particle size of 30 microns and an average particle size of 200 microns by screening, with the mass fraction of the fine aluminum alloy powder being 70% and the mass fraction of the coarse aluminum alloy powder being 30%.

[0049] Room temperature mechanical property tests along the extrusion direction show that the yield strength of the Al-6.2Zn-2.3Mg-2.3Cu-0.1Zr aluminum alloy sheet is 700MPa, the tensile strength is 740MPa, and the elongation is 13%; the stress intensity factor range ΔK is 20MPa.m 0.5 When the fatigue crack growth rate is 7.5×10 -4 mm / cycle.

[0050] Example 6

[0051] The similarities with Example 4 are not repeated here. The differences are as follows: the atomization process parameters are adjusted (pressure 9 MPa, flow rate 400 m / s), and fine aluminum alloy powder with an average particle size of 50 μm and coarse aluminum alloy powder with an average particle size of 300 μm are obtained by screening; the mass fraction of the fine aluminum alloy powder is 60%, and the mass fraction of the coarse aluminum alloy powder is 40%; the aging process is a two-stage aging treatment, and the process parameters are 120°C for 30 min and then 50°C for 720 h.

[0052] Room temperature mechanical property tests along the extrusion direction show that the yield strength of the Al-6.2Zn-2.3Mg-2.3Cu-0.1Zr aluminum alloy sheet is 710MPa, the tensile strength is 750MPa, and the elongation is 12%; the stress intensity factor range ΔK is 20MPa.m 0.5 When the fatigue crack growth rate is 8.5×10 -4 mm / cycle.

[0053] Example 7

[0054] The similarities with Example 6 are not repeated here. The differences are as follows: the aluminum alloy powders used are two aluminum alloy compositions: Al-4.2Cu-1.8Mg-0.5Mn (mass fraction, %) and Al-6.2Zn-2.3Mg-2.3Cu-0.2Zr-0.1Sc. The fine aluminum alloy powder with an average particle size of 50 μm is composed of Al-4.2Cu-1.8Mg-0.5Mn, and the coarse aluminum alloy powder with an average particle size of 200 μm is composed of Al-6.2Zn-2.3Mg-2.3Cu-0.2Zr-0.1Sc. The mass fraction of the fine aluminum alloy powder is 60%, and the mass fraction of the coarse aluminum alloy powder is 40%. The solution treatment adopts a two-stage solution treatment, with a temperature of 470°C for 30 minutes, then a temperature of 505°C for 30 minutes, followed by rapid water quenching with a transfer time of less than or equal to 15 seconds. After the water quenching, cold deformation treatment is immediately performed, and the thickness deformation after room temperature rolling is 5%. Finally, a two-stage aging treatment was carried out, with a heat preservation of 180℃ for 10min and then a heat preservation of 80℃ for 720h.

[0055] Room temperature mechanical property tests along the extrusion direction show that the yield strength of the aluminum alloy sheet is 560MPa, the tensile strength is 690MPa, and the elongation is 14%; the stress intensity factor range ΔK is 20MPa.m 0.5 When the fatigue crack growth rate is 7×10 -4 mm / cycle.

[0056] Comparative Example 1

[0057] The implementation steps of this comparative example are basically the same as those of Example 1, except that:

[0058] The Al-Cu-Mg plate is prepared by alloy powder with a single particle size distribution and an average particle size of 10 μm. The aging process adopts a conventional aging treatment process with process parameters of 180°C insulation for 20 h and no cold deformation treatment before aging.

[0059] The room temperature mechanical property test along the rolling direction shows that the yield strength of the Al-4.2Cu-1.8Mg-0.5Mn aluminum alloy plate is 320 MPa, the tensile strength is 490 MPa, and the elongation is 16%; the stress intensity factor range ΔK is 20 MPa.m 0.5 , and the fatigue crack propagation rate is 6.5×10 -4 mm / cycle. Compared with the above, the yield strength, the tensile strength and the elongation of the material of the embodiment 1 of the present application are all improved, and the fatigue crack propagation rate is significantly reduced.

[0060] Comparative Example 2

[0061] The specific steps of the present comparative example are basically the same as those of the embodiment 1, except that the Al-Cu-Mg plate is prepared by using the alloy powder with a single particle size distribution, and the average particle size of the alloy powder is 10 microns.

[0062] The room temperature mechanical property test along the rolling direction shows that the yield strength of the Al-4.2Cu-1.8Mg-0.5Mn aluminum alloy plate is 460 MPa, the tensile strength is 580 MPa, and the elongation is 12%; the stress intensity factor range ΔK is 20 MPa.m 0.5 , and the fatigue crack propagation rate is 7.5×10 -4 mm / cycle. Compared with the above, the tensile strength and the elongation of the material of the embodiment 1 of the present application are both improved, and the fatigue crack propagation rate is reduced by nearly two times.

[0063] Comparative Example 3

[0064] The specific steps of the present comparative example are basically the same as those of the embodiment 1, except that the aging treatment is the conventional aging treatment, and the specific aging process parameters are 180℃ for 20h, and no cold deformation treatment before aging.

[0065] The room temperature mechanical property test along the rolling direction shows that the yield strength of the Al-4.2Cu-1.8Mg-0.5Mn aluminum alloy plate is 300 MPa, the tensile strength is 485 MPa, and the elongation is 17%; the stress intensity factor range ΔK is 20 MPa.m 0.5 , and the fatigue crack propagation rate is 6×10 -4 mm / cycle. Compared with the above, the strength and the elongation of the material of the embodiment 1 of the present application are both improved, and the fatigue crack propagation rate is reduced.

[0066] Comparative Example 4

[0067] The specific steps of the present comparative example are basically the same as those of the embodiment 1, except that the aging treatment is the conventional aging treatment, and the specific aging process parameters are 180℃ for 20h.

[0068] Room temperature mechanical property tests along the rolling direction show that the yield strength of Al-4.2Cu-1.8Mg-0.5Mn aluminum alloy plate is 450MPa, the tensile strength is 575MPa, and the elongation is 11%; the stress intensity factor range ΔK is 20MPa.m 0.5 When the fatigue crack growth rate is 7.5×10 -4 In comparison, the strength and elongation of the material of Example 1 of the present invention are both improved while the fatigue crack growth rate is reduced by nearly two times.

[0069] Comparative Example 5

[0070] The implementation steps of this comparative example are basically the same as those of Example 2. The difference from Example 2 is that the Al-Cu-Mg plate is prepared using alloy powder with a single particle size distribution and a conventional aging treatment process. The average particle size of the alloy powder is 200 μm. The aging process parameters are 180° C. for 20 h, and no cold deformation treatment is performed before aging.

[0071] Room temperature mechanical property tests along the rolling direction show that the yield strength of Al-4.2Cu-1.8Mg-0.5Mn aluminum alloy plate is 280MPa, the tensile strength is 470MPa, and the elongation is 18%; the stress intensity factor range ΔK is 20MPa.m 0.5 When the fatigue crack growth rate is 5.5×10 -4 In comparison, the strength and elongation of the material of Example 2 of the present invention are both improved while the fatigue crack growth rate is reduced by nearly two times.

[0072] Comparative Example 6

[0073] The specific steps of this comparative example are basically the same as those of Example 2, except that the Al-Cu-Mg plate is prepared using alloy powder with a single particle size distribution, and the average diameter of the powder is 10 microns.

[0074] Room temperature mechanical property tests along the rolling direction show that the yield strength of Al-4.2Cu-1.8Mg-0.5Mn aluminum alloy plate is 380MPa, the tensile strength is 510MPa, and the elongation is 16%; the stress intensity factor range ΔK is 20MPa.m 0.5 When the fatigue crack growth rate is 7×10 -4 In comparison, the strength and elongation of the material of Example 2 of the present invention are both improved while the fatigue crack growth rate is reduced by more than 2 times.

[0075] Comparative Example 7

[0076] The specific steps of this comparative example are basically the same as those of Example 3, except that: the Al-Cu-Mg plate is prepared using alloy powder with a single particle size distribution, and the average diameter of the powder is 600 microns.

[0077] Room temperature mechanical property tests along the rolling direction show that the yield strength of Al-4.2Cu-1.8Mg-0.5Mn aluminum alloy plate is 220MPa, the tensile strength is 450MPa, and the elongation is 18%; the stress intensity factor range ΔK is 20MPa.m 0.5 When the fatigue crack growth rate is 5×10 -4 In comparison, the strength and elongation of the material of Example 3 of the present invention are both improved while the fatigue crack growth rate is significantly reduced.

[0078] Comparative Example 8

[0079] The specific steps of this comparative example are basically the same as those of Example 3, except that the Al-Cu-Mg plate adopts a conventional aging process with specific process parameters of 180° C. insulation for 20 h.

[0080] Room temperature mechanical property tests along the rolling direction show that the yield strength of Al-4.2Cu-1.8Mg-0.5Mn aluminum alloy plate is 270MPa, the tensile strength is 475MPa, and the elongation is 18%; the stress intensity factor range ΔK is 20MPa.m 0.5 When the fatigue crack growth rate is 5.5×10 -4 In comparison, the strength and elongation of the material of Example 3 of the present invention are both improved while the fatigue crack growth rate is significantly reduced.

[0081] Comparative Example 9

[0082] This comparative example is basically the same as Example 4, except that alloy powder with a single particle size distribution is used, and its average particle size is 200 microns.

[0083] Room temperature mechanical property tests along the extrusion direction show that the yield strength of the Al-6.2Zn-2.3Mg-2.3Cu-0.1Zr aluminum alloy sheet is 660MPa, the tensile strength is 690MPa, and the elongation is 8%; the stress intensity factor range ΔK is 20MPa.m 0.5 When the fatigue crack growth rate is 1.0×10 -3 In comparison, the strength and elongation of the material of Example 4 of the present invention are both improved while the fatigue crack growth rate is significantly reduced.

[0084] Comparative Example 10

[0085] This comparative example is basically the same as Example 4, except that: alloy powder with a single particle size distribution and a conventional aging treatment process are used, the average particle size is 30 μm, the aging treatment process parameters are 120° C. for 20 hours, and no cold deformation treatment is performed before aging.

[0086] Room temperature mechanical property tests along the extrusion direction show that the yield strength of the Al-6.2Zn-2.3Mg-2.3Cu-0.1Zr aluminum alloy sheet is 675MPa, the tensile strength is 700MPa, and the elongation is 7%; the stress intensity factor range ΔK is 20MPa.m 0.5 When the fatigue crack growth rate is 1.5×10 -3 In comparison, the strength and elongation of the material of Example 4 of the present invention are both improved while the fatigue crack growth rate is significantly reduced.

[0087] Comparative Example 11

[0088] This comparative example is basically the same as Example 6, except that: alloy powder with a single particle size distribution and a conventional aging process are used, the average particle size is 50 μm, the aging process parameters are 120° C. for 20 h, and no cold deformation treatment is performed before aging.

[0089] Room temperature mechanical property tests along the extrusion direction show that the yield strength of the Al-6.2Zn-2.3Mg-2.3Cu-0.1Zr aluminum alloy sheet is 680MPa, the tensile strength is 710MPa, and the elongation is 10%; the stress intensity factor range ΔK is 20MPa.m 0.5 When the fatigue crack growth rate is 1×10 -3 In comparison, the strength and elongation of the material of Example 6 of the present invention are both improved while the fatigue crack growth rate is significantly reduced.

[0090] Comparative Example 12

[0091] This comparative example is basically the same as Example 6, except that conventional aging treatment is adopted, the process parameters of which are 120°C insulation for 20 hours, and no cold deformation treatment is performed before aging.

[0092] Room temperature mechanical property tests along the extrusion direction show that the yield strength of the Al-6.2Zn-2.3Mg-2.3Cu-0.1Zr aluminum alloy sheet is 620MPa, the tensile strength is 670MPa, and the elongation is 11%; the stress intensity factor range ΔK is 20MPa.m 0.5 When the fatigue crack growth rate is 9.3×10 -4 In comparison, the strength and elongation of the material of Example 6 of the present invention are both improved while the fatigue crack growth rate is significantly reduced.

[0093] Comparative Example 13

[0094] This comparative example is basically the same as Example 7, except that conventional aging treatment is adopted, the process parameters of which are 180°C insulation for 20 hours, and no cold deformation treatment is performed before aging.

[0095] Room temperature mechanical property tests along the extrusion direction show that the yield strength of the aluminum alloy sheet is 450MPa, the tensile strength is 570MPa, the elongation is 12%; the stress intensity factor range ΔK is 20MPa.m 0.5 When the fatigue crack growth rate is 8.0×10 -4 In comparison, the strength and elongation of the material of Example 7 of the present invention are both improved while the fatigue crack growth rate is significantly reduced.

[0096] The above describes the specific embodiments of the present invention. It can be seen from Examples 1-7 that the method provided by the present invention can be applied to different alloy materials, and can achieve improvements in the strength, elongation and fatigue crack propagation resistance of different alloy materials. By comparing Examples 1-3 with Comparative Examples 1-8, Examples 4-6 with Comparative Examples 9-12, and Example 7 with Comparative Example 13, the method of the present invention provides a method for preparing a high-strength, low-fatigue crack propagation rate aluminum alloy material. Due to the use of coarse and fine powders of specific particle sizes for proportioning, the material is treated under aging treatment conditions different from conventional aging treatment processes, and combined with processes such as cold deformation treatment, the strength, elongation and fatigue crack propagation resistance of the aluminum alloy can be improved at the same time.

[0097] It should be understood that the present invention is not limited to the specific embodiments described above, and that those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of the present application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

Claims

1. A method for preparing a high-strength and low-fatigue crack growth rate aluminum alloy material, characterized in that: The steps include: (1) Screening two types of aluminum alloy powders with different particle size distributions, the first type being fine aluminum alloy powder with an average particle size of 10-60 μm, wherein the weight proportion of the fine aluminum alloy powder is 60%-80%; the second type being coarse aluminum alloy powder with an average particle size of 50-600 μm; the ratio of the average particle size of the coarse aluminum alloy powder to the fine aluminum alloy powder is (5-10):1; (2) After the above-mentioned fine aluminum alloy powder and coarse aluminum alloy powder are fully mixed, vacuum degassing and hot isostatic pressing are performed to obtain an aluminum alloy ingot with a density of ≥99.5%; the vacuum degassing and hot isostatic pressing treatment is as follows: first, a metal sheath is used, the heating temperature is 450-550°C, the vacuum degree inside the metal sheath is equal to 0.1Pa, and then hot isostatic pressing is performed, the pressure is greater than or equal to 100MPa, the hot pressing temperature is 450-550°C, the holding time is 2-8h, and then the heat is continued for 12-24h under no external pressure to perform homogenization treatment, and finally air cooling is performed, and the density of the obtained aluminum alloy ingot is ≥99.5%; (3) subjecting the aluminum alloy ingot to homogenization annealing treatment, air cooling, and then plastic forming to obtain a heterogeneous structure aluminum alloy material having a coarse-fine grain distribution; the homogenization annealing treatment is performed at 450-500°C for 6-12 hours; the plastic forming method is hot rolling or hot extrusion; (4) subjecting the above-mentioned heterogeneous structure aluminum alloy material containing a coarse-fine grain distribution to a solution treatment, wherein the solution treatment comprises heating, holding and water quenching steps; performing a cold deformation treatment after the solution treatment, wherein the deformation amount is 3%-30%, and the interval between the solution treatment and the end time is less than or equal to 1 hour; obtaining the deformed heterogeneous structure aluminum alloy material; wherein the cold deformation treatment is rolling or stretching, and the deformation temperature range is -50°C to 50°C; (5) The deformed heterogeneous aluminum alloy material is subjected to single-stage aging or two-stage aging treatment.

2. The method for preparing a high-strength and low-fatigue crack growth rate aluminum alloy material according to claim 1, characterized in that: The coarse aluminum alloy powder and the fine aluminum alloy powder are approximately spherical.

3. The method for preparing a high-strength and low-fatigue crack growth rate aluminum alloy material according to claim 1, characterized in that: In the step (3), the hot rolling is as follows: the rolling start temperature is 420°C, the hot rolling is terminated when the total thickness deformation is greater than or equal to 98%, and annealing is performed, the annealing temperature is 400°C, the temperature is kept for 0.5h, and cold rolling is performed after air cooling. After multiple passes, the aluminum alloy thin plate is formed, and the total thickness deformation of the cold rolling is greater than or equal to 60%. No annealing is performed during the cold rolling process. The hot extrusion is as follows: the extrusion temperature is 420°C, and the plate is extruded to the target thickness.

4. The method for preparing a high-strength and low-fatigue crack growth rate aluminum alloy material according to claim 1, characterized in that: In the step (4), the solution treatment is a single-stage solution treatment or a double-stage solution treatment. The single-stage solution treatment is as follows: heating to a temperature of 450-550°C, holding for 45-60 minutes, followed by rapid water quenching, and the transfer time is less than or equal to 15 seconds; the double-stage solution treatment is as follows: holding at a temperature of 470°C for 30 minutes, then holding at 505°C for 30 minutes, followed by rapid water quenching, and the transfer time is less than or equal to 15 seconds.

5. The method for preparing a high-strength and low-fatigue crack growth rate aluminum alloy material according to claim 1, characterized in that: In the step (5), the single-stage aging treatment is 80-120°C, and the heat preservation is 48h-720h; the two-stage aging treatment is: 120°C-195°C, heat preservation for 10-30min, and then 50-100°C, and heat preservation for 48h-720h.