Cross-series difference light high-strength corrosion-resistant aluminum alloy and preparation method thereof

Abstract

The invention discloses a novel cross-series difference light high-strength corrosion-resistant aluminum alloy and a preparation method thereof. Alloy components break through an existing aluminum alloy component system and comprise the following alloy elements in percentage by weight: 2-3.5 wt% of Mg, 1-2 wt% of Cu, 0.3-0.8 wt% of Li, 0-0.5 wt% of Si, at least two microalloy elements of Zr, Hf, Ti, V, Nb, Y, Sc or Er with the Mg / Cu weight ratio of 1.5-2 and the total content not exceeding 1 wt%, and the balance of Al and inevitable impurities. The preparation method of the alloy comprises the following steps: (1) casting the aluminum alloy; (2) homogenizing heat treatment; (3) carrying out thermal deformation to obtain a hot working material; (4) optionally obtaining a cold working material through cold deformation; and (5) the machined material is subjected to solid solution and aging treatment, and a finished product material is obtained. The aluminum alloy material shows excellent comprehensive service performance, including low specific gravity (2.64-2.67 g / cm < 3 >, lower than that of pure aluminum), high strength (peak aging tensile strength 430-460 MPa), excellent plasticity / toughness (peak aging elongation gt; the product of strength and elongation is gt; the stress corrosion resistance (the stress corrosion sensitivity coefficient is smaller than or equal to 5%) is achieved, and wide engineering application prospects are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum alloys and their preparation and processing. More specifically, the present invention relates to a cross-series difference lightweight, high-strength and corrosion-resistant aluminum alloy and a preparation method thereof. Background Art

[0002] In order to better meet the actual application requirements and achieve the purpose of weight reduction and energy conservation, it is urgent for aluminum alloys to break through the shackles of the existing alloy system, design and prepare a new type of low-density, high-strength and corrosion-resistant aluminum alloy with cross-series difference.

[0003] Traditional aluminum alloys can be divided into eight series according to alloying components, and generally have advantages such as low density, high specific strength, corrosion resistance, good plasticity and processing performance, and low cost, and have been widely used in the fields of aerospace, national defense, transportation, etc. 1, 3, 4, and 5 series aluminum alloys are non-heat-treatable strengthening alloys. Among them, the 1 series is industrial pure aluminum with an aluminum content greater than 99%, which has good corrosion resistance and welding performance but extremely low strength, less than 100 MPa. The 3 series is an Al-Mn alloy, and its main performance characteristics are excellent corrosion resistance, plasticity and welding performance, but the Al-Mn alloy has low strength, only slightly higher than industrial pure aluminum. The 4 series is an Al-Si alloy, which has good melt fluidity, heat resistance and welding performance, but poor plasticity and low strength, and is mostly used for casting alloys. The 5 series is an Al-Mg alloy, which has low density, good corrosion resistance and welding performance, but relying on solid solution strengthening and work hardening, the strength is only ~300 MPa, and there are also problems such as poor formability and low yield rate.

[0004] 2, 6, and 7 series aluminum alloys are heat-treatable alloys. Among them, the 2 series is an Al-Cu(-Mg) alloy, which can disperse and precipitate a large number of θ'-Al2Cu and S-Al2CuMg phases during aging, achieving a high strength of 500 MPa level, and having good toughness and welding performance. However, the high strength of the 2 series aluminum alloy strongly depends on a high Cu content, resulting in a significantly higher specific gravity of the alloy (generally >2.8 g / cm 3 ). The 7 series is an Al-Zn-Mg(-Cu) alloy, which can disperse and precipitate a large number of η'-Mg2Zn3Al4 phases during aging, achieving an ultra-high strength of 700 MPa level. However, the high strength of the 7 series aluminum alloy strongly depends on high Zn and Cu contents, resulting in an even higher specific gravity of the alloy, and due to excessive precipitation at grain boundaries, it is easy to form a continuous network distribution, resulting in poor plasticity and corrosion resistance of the alloy. The 6 series is an Al-Mg-Si alloy, and the addition amounts of Mg and Si generally do not exceed 1 wt%, but some other elements such as Mn and Cr are also added at the same time. The alloy has low cost and good formability and welding performance, but because the element addition amounts are low, the alloy strength is not high, generally not exceeding 400 MPa.

[0005] The 8 series is an alloy with other elements as the main alloying elements, such as Al-Li alloy. Li is the lightest metal element, and the main alloying of Li enables the alloy to achieve extremely low density. After the aging process, the δ'-Al3Li phase is dispersed and precipitated, which can reach a medium strength of 300MPa. However, during deformation, the movable dislocation can easily cut through the δ' phase, and the coplanar slip causes severe local strain, which will significantly reduce the ductility and fracture toughness of the alloy. In addition, Li has a low melting point and active chemical properties. It is very volatile during the smelting process and is very easy to react with elements such as oxygen. If the Li content is too high, defects such as pores, thermal cracks and burns are easily generated during the welding process, resulting in poor welding performance of the alloy.

[0006] In order to improve the comprehensive performance of traditional aluminum alloys, some new aluminum alloys have been developed in recent years at home and abroad, aiming to break the main element restrictions of the existing composition system aluminum alloys, and combined with multi-element microalloying design, good results have been achieved. For example:

[0007] (1) Patent document CN 115369294A discloses a novel heat-resistant Al-Mg-Cu-Zn alloy and its heat treatment process (alloy composition: 2.2-3.5wt% Mg; 1.0-1.5wt% Cu; 1.5-4.5wt% Zn; 0-0.3wt% Si; 0.0-0.5wt% Mn). Based on the Al-Mg-Cu alloy composition with a low Cu / Mg ratio, by adding new main alloying elements Zn and microalloying elements Si, a high-strength (hardness 170HV) Al-Mg-Cu-Zn-Si alloy can be obtained by adopting a double-stage aging process. However, the high Cu and Zn contents significantly reduce the lightweight advantage of the Al-Mg alloy, and the specific gravity exceeds that of pure aluminum (>2.7g / cm 3 ), and the patent only discloses the hardness curve, and other mechanical properties and corrosion properties are not reported;

[0008] (2) Patent document CN 113943880A discloses an Al-Cu-Li-Mg-V-Zr-Sc-Ag alloy and its preparation method (alloy composition: 0.2-0.8wt% Mg; 2.0-4.5wt% Cu; 0.5-3.0wt% Li; 0.1-0.7wt% Ag; 0.1-0.5wt% Mn). Based on the 2-series Al-Cu-Li alloy composition, a high strength of 560MPa can be achieved through microalloying of Mg and Ag combined with work hardening. However, the second phase on the alloy grain boundary reduces the corrosion resistance of the alloy. In order to reduce the specific gravity, a high Cu content must be combined with a high Li content, and a high Li content is prone to precipitating more Al3Li, which will further damage the alloy elongation (<10%).

[0009] (3) Patent document CN 118621189 A discloses a high-strength 5-series ultra-thin aluminum alloy and its preparation method (alloy composition: 3.0 - 7.0 wt% Mg; 0.1 - 0.5 wt% Cu; 0.2 - 0.8 wt% Li; 0.1 - 0.5 wt% Mn). Based on the 5-series Al-Mg alloy composition, through the microalloying of Cu and Li, it is possible to improve the strength of the 5-series alloy while maintaining the advantages of light weight and corrosion resistance. However, due to the strong reliance on the solid solution strengthening mechanism of a single main element Mg, the strength is still low. Although the higher the Mg content, the more beneficial it is to improve the alloy strength, it will seriously damage the alloy plasticity and formability. The patent does not mention the alloy precipitation behavior, and it is still uncertain whether there is a precipitation strengthening effect. However, considering that both Cu and Li are added in trace amounts, even if new precipitated phases containing Cu and Li are formed, it will be difficult to obtain an obvious precipitation strengthening effect due to the extremely limited quantity.

[0010] (4) Patent document CN 108193101 A discloses an Er, Zr, Si microalloyed A1-Mg-Cu alloy and its thermomechanical treatment process (alloy composition: 1.8 - 2.2 wt% Mg; 0.7 - 0.9 wt% Cu; 0.11 - 0.15 wt% Si). Also based on the 5-series Al-Mg alloy composition and Cu microalloying, but further using microalloying such as Er, Zr, Si, etc. to refine the grains and increase the recrystallization temperature. The alloy specific gravity is close to that of pure aluminum, and the subsequent thermomechanical treatment can improve both strength and plasticity at the same time. Among them, pre-deformation after solution treatment can effectively inhibit natural aging hardening and reduce the influence of room temperature storage on artificial aging. However, similarly, due to the trace addition of Cu, Er, Zr, Si, etc., it is difficult to achieve an obvious precipitation strengthening effect, and the alloy strength is still not high (<350 MPa).

[0011] (5) Patent document JP2010018854A discloses a lightweight high-strength aluminum alloy with excellent heat resistance (alloy composition: 1.5 - 2.2 wt% Mg; 2.5 - 3.3 wt% Cu; 0.2 - 0.4 wt% Si; 0.5 - 1.0 wt% Fe; 0.8 - 1.3 wt% Ni;; 0.4 - 0.7 wt% Mn). Based on the 2-series Al-Cu-Mg composition, through the microalloying of Si, Fe, Ni, Mn, etc., the heat resistance of the alloy is improved, and the tensile strength can reach more than 500 MPa. However, due to the relatively large addition amounts of high-specific gravity elements such as Cu, Fe, Ni, Mn, etc., the alloy specific gravity exceeds 2.8 g / cm 3 , and the solid solubility of Fe, Ni, Mn, etc. in the aluminum alloy is relatively low, resulting in a large amount of second phases distributed along the grain boundaries, deteriorating the plasticity and corrosion resistance of the alloy.

[0012] (6) Patent document CN 118006980A discloses a super-light and high-strength aluminum-lithium alloy with high Mg content and its preparation method (alloy composition: 4.0 - 6.0 wt% Mg; 0.1 - 1.0 wt% Cu; 1.0 - 2.5 wt% Li). By using vacuum induction melting, an Al-Mg-Li alloy with obvious lightweight advantages was obtained, with a specific gravity as low as 2.20 - 2.50 g / cm 3 , the tensile strength is above 400 MPa, but high Mg (>4 wt%) and high Li content, as well as an excessive Mg / Cu ratio (>4), easily lead to coarse second phases at grain boundaries and a relatively large amount of Al3Li in the grains, seriously damaging the plasticity (elongation <7%) and corrosion resistance of the alloy.

[0013] Although in recent years, new aluminum alloys have been developed through cross-series difference design, especially based on Al-Mg, and some achievements have been made in researching new alloys with excellent comprehensive properties, there is still much room for improvement in balancing low specific gravity, high strength, high toughness, and corrosion resistance. The types and amounts of alloying elements added are not reasonable: Although the Mg element reduces the specific gravity, a high Mg content (>5 wt%) leads to the distribution of a relatively large number of Al3Mg2 phases along the grain boundaries, deteriorating the corrosion resistance of the alloy; Although Zn / Cu elements can increase the precipitation phase density of the alloy and significantly improve the alloy strength, a high Zn / Cu content loses the low specific gravity advantage of aluminum alloys; Although the Li element significantly reduces the specific gravity of the alloy, a high Li content leads to the massive precipitation of Al3Li phases, which will significantly reduce the plastic toughness of the alloy. In addition, the solid solubility of other common elements in Al alloys is limited (<1 wt%), and it is difficult to play an important role in the synergy of low specific gravity, high strength, high toughness, and corrosion resistance. Summary of the Invention

[0014] In view of this, the purpose of the present invention is to provide a new type of cross-series difference lightweight, high-strength, and corrosion-resistant aluminum alloy and its preparation method.

[0015] The present invention is achieved through the following technical solutions:

[0016] Provide a cross-series difference lightweight, high-strength, and corrosion-resistant aluminum alloy. The alloy composition breaks the existing aluminum alloy composition system and includes the following alloying elements and weight percentage contents: Mg: 2 - 3.5 wt%, Cu: 1 - 2 wt%, Li: 0.3 - 0.8 wt%, Si: 0 - 0.5 wt%, Mg / Cu weight ratio = 1.5 - 2, and at least two of the micro-alloying elements Zr, Hf, Ti, V, Nb, Y, Sc, or Er with a total content not exceeding 1 wt%, and the balance is Al and unavoidable impurities; the specific gravity of the aluminum alloy is 2.64 - 2.67 g / cm 3 , the tensile strength is 430 - 460 MPa, the elongation >12%, the strength-plasticity product >5.5 GPa%, and the stress corrosion sensitivity coefficient ≤5%.

[0017] Furthermore, the alloy composition design breaks the existing 2XXX, 5XXX, 6XXX, and 8XXX aluminum alloy composition series. By adding the main elements Mg and Cu, sufficient precipitation of the main strengthening phase, the GPB zone, is obtained; the addition of the elements Li and Si not only helps to reduce the specific gravity of the alloy but also promotes the precipitation of GPB. When adding Li and Si simultaneously, the precipitation of GPB can be significantly promoted, and the intragranular precipitation quantity of GPB can be significantly increased. In addition, Si can dissolve into the S phase, and Li can coat the S phase at the interface. Both are beneficial to reducing the free energy and electrode potential of the S phase, improving the thermodynamic and chemical stability, delaying its coarsening rate, and improving the distribution state of the grain boundary S phase in the peak aging state, that is, changing from the common continuous network distribution along the grain boundary to a discontinuous distribution. Thus, while the aluminum alloy obtains high strength in peak aging, good corrosion resistance can be achieved; at least two of the microalloying elements Zr, Hf, Ti, V, Nb, Y, Sc, or Er are added to form a composite structure L12 phase, ultimately enabling the aluminum alloy to have the co-precipitation strengthening of multiple different scale nanophases of GPB, S, and L12; among them, GPB is the main strengthening phase, highly coherent with the matrix, with a size of 20 - 50 nm and a number density of ~10 16 / m 2 ; the L12 phase and the S phase are secondary strengthening phases, coherent or semi-coherent with the matrix, with a size of 5 - 20 nm and a number density of ~10 14 / m 2 .

[0018] Furthermore, the total addition amount of all the alloying elements < 7 wt%.

[0019] A preparation method of a cross-series differential lightweight, high-strength, and corrosion-resistant aluminum alloy is also provided, including the following steps:

[0020] Step S1: Melting to obtain an aluminum alloy ingot of the cross-series differential lightweight, high-strength, and corrosion-resistant aluminum alloy described above;

[0021] Step S2: Performing homogenization treatment on the obtained aluminum alloy ingot;

[0022] Step S3: After skimming the homogenized aluminum alloy ingot, performing preheating / heat preservation;

[0023] Step S4: By using one or more hot deformation processing methods selected from extrusion, rolling, drawing, and forging, thermally deforming the heat-preserved aluminum alloy ingot into a required processed material / pre-processed material;

[0024] Step S5: Optionally, performing re-annealing treatment on the pre-processed material and then cold-deforming it into a required processed material;

[0025] Step S6: Perform solution quenching heat treatment and natural / artificial aging heat treatment on the processed material obtained in Step S4 or Step S5.

[0026] Further, in Step S1, the ingot is manufactured by the ingot smelting method; pure aluminum and various intermediate alloys are loaded into a graphite crucible and heated to melt; after skimming the slag, pure magnesium is added, and after complete melting, degassing and slag skimming are carried out; then pure Li is pressed into the melt, and after slag removal, it is allowed to stand, and finally, casting is carried out using a water-cooled copper mold under argon protection.

[0027] Further, in Step S2, the homogenization treatment is carried out as follows: in the range of 350 °C to 520 °C, single-stage, double-stage or multi-stage homogenization heat treatment is carried out for a total time of 12 to 72 h.

[0028] Further, in Steps S3 and S4, the holding temperature and the hot deformation temperature are kept the same: the holding temperature, the hot deformation processing temperature for each time, and the reheating temperature are 370 - 460 °C, and the treatment time is 1 - 5 h.

[0029] Further, in Step S6, the solution heat treatment system is: in the range of 480 - 520 °C, single-stage, double-stage or multi-stage solution heat treatment is carried out for a total time of 0.5 - 5 h.

[0030] Further, in Step S6, the natural / artificial aging heat treatment is carried out by one of the following methods:

[0031] (1) Within 1 h after completion of quenching and cooling, artificial aging treatment is carried out in the range of 70 - 300 °C for a total time of 3 - 100 h;

[0032] (2) After completion of quenching and cooling, a combination of natural aging and artificial aging is adopted, with the artificial aging temperature being 70 - 300 °C and the total time being 3 - 100 h.

[0033] Further, the artificial aging heat treatment is carried out by single-stage, double-stage aging or three-stage T77 aging.

[0034] Further, the preparation method is replaced by powder metallurgy or additive printing.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] The component design of this alloy belongs to the compositional optimization design carried out with a cross-series difference. By adding the main elements Mg and Cu, sufficient precipitation of the main strengthening phase GPB is obtained; the addition of elements Li and Si not only helps to reduce the alloy density but also promotes the precipitation of GPB. Especially when Li and Si are added simultaneously, the precipitation of GPB can be significantly promoted, and the intragranular precipitation quantity of GPB can be significantly increased. In addition, Si can dissolve into the S phase, and Li can coat the S phase at the interface. Both are beneficial to reducing the free energy and electrode potential of the S phase, improving its thermodynamic and chemical stability, which can not only delay its coarsening rate but also improve the distribution state of the S phase at the grain boundary in the peak aging state (i.e., change from the common continuous network distribution along the grain boundary to a discontinuous distribution), so that while the alloy obtains high strength in peak aging, good corrosion resistance can be achieved. Microalloying elements such as Zr, Hf, Ti, V, Nb, Y, Sc, or Er are added to form the composite structure L12 phase, ultimately enabling the aluminum alloy to have the co-precipitation strengthening of multiple different scale nano-phases of GPB, S, and L12, and finally obtaining a new type of lightweight, high-strength, and corrosion-resistant aluminum alloy with a physical density of 2.64 - 2.67 g / cm 3 , a tensile strength of more than 430 MPa, an elongation rate > 12%, a strength-ductility product > 5.5 GPa%, and a stress corrosion sensitivity coefficient ≤ 5%. While ensuring low density, it also has high strength, plasticity, and good corrosion resistance, showing excellent comprehensive performance and being an ideal material for various load-bearing structural parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0038] Figure 1 It is the aging hardening curve at 200 °C of the lightweight, high-strength, and corrosion-resistant aluminum alloy material prepared in Example 1 of the present invention.

[0039] Figure 2 It is the room temperature tensile curve of the lightweight, high-strength, and corrosion-resistant aluminum alloy material prepared in Example 1 of the present invention under peak aging.

[0040] Figure 3 It is the slow stress tensile curve of the lightweight, high-strength, and corrosion-resistant aluminum alloy material prepared in Example 1 of the present invention in different media under peak aging state.

[0041] Figure 4 It is the HAADF image of the multi-phase co-precipitation of the lightweight, high-strength, and corrosion-resistant aluminum alloy material prepared in Example 1 of the present invention under peak aging.

[0042] Figure 5 HAADF image of the grain boundary of the lightweight, high-strength and corrosion-resistant aluminum alloy material prepared in Example 1 of the present invention under peak aging. Detailed implementation manners

[0043] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention, and to make the above-mentioned objects, features, and advantages of the present invention more obvious and understandable, the following further describes the specific implementation manners of the present invention.

[0044] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0045] The following elaborates in detail on the lightweight, high-strength and corrosion-resistant materials provided by the present invention and their preparation methods through specific embodiments.

[0046] Example 1

[0047] Step S1: Weigh raw materials according to the weight percentages of the following components: Mg 3wt%; Cu 2wt%; Li 0.5wt%; Si 0.2wt%; Sc 0.15wt%; Zr 0.2wt%; Ti 0.1wt%; the balance is pure aluminum;

[0048] Step S2: Load pure aluminum and Al-50Cu, Al-10Si, Al-5Zr, Al-2Sc, Al-10Ti master alloys into a graphite crucible and heat to melt; after skimming the slag, add pure magnesium, degas and skim the slag after complete melting; then press pure Li into the melt, remove the slag and let it stand, and finally cast using a water-cooled copper mold under argon protection.

[0049] Step S3: Perform homogenization treatment on the obtained aluminum alloy ingot: perform the first-stage homogenization heat treatment at 420°C for 10 h, and then raise the temperature to 510°C at a rate of 10°C / min for the second-stage homogenization heat treatment for 18 h;

[0050] Step S3: After peeling the homogenized aluminum alloy ingot, keep it warm at 450°C for 2 h; then perform hot rolling at the same temperature, control the total reduction in thickness within 80% ± 4%, and the reduction in thickness per pass is ~20%;

[0051] Step S4: Perform solution quenching heat treatment on the processed material obtained by hot rolling: perform two-stage solution heat treatment of 505°C / 1 h + 510°C / 0.5 h, and immediately perform water quenching after completion;

[0052] Step S5: Perform natural / artificial aging heat treatment on the quenched sheet: within 1 h after completion of quenching and cooling, perform artificial aging treatment within the range of 200 ± 2 °C, and the total time is 0 - 75 h;

[0053] After detection, the physical specific gravity of the experimental alloy is 2.65 g / cm 3 ; Perform aging heat treatment on the experimental alloy, Figure 1 is the aging hardening curve of the alloy prepared in Example 1 of the present invention at 200 °C. The alloy reaches peak aging at about 25 h, and the hardness value is 140.8 HV 0.2 ; Figure 2 is the room temperature tensile curve of the alloy prepared in Example 1 of the present invention in the peak aging state. The yield strength of the alloy is 368 MPa, the tensile strength is 462 MPa, the total elongation is 12.6%, and the strength-ductility product reaches 5.8 GPa%; Figure 3 is the slow stress tensile curve of the alloy prepared in Example 1 of the present invention in different media in the peak aging state. The results show that the stress corrosion sensitivity index of the alloy is about 5%. Therefore, the alloy exhibits a good match of low density - high strength - high toughness - corrosion resistance. In addition, Figure 4 is the HAADF image of the multi-phase combined precipitation of the alloy prepared in Example 1 of the present invention under peak aging. The image shows that the alloy is strengthened by multiple phases such as L12, GPB, and S phases, revealing the potential of the alloy to have good mechanical properties. Among them, GPB is the main strengthening phase, and it is highly coherent with the matrix, with a size of 20 - 50 nm and a number density of ~10 16 / m 2 ; The L12 phase and the S phase are secondary strengthening phases, coherent or semi-coherent with the matrix, with a size of 5 - 20 nm and a number density of ~10 14 / m 2 . Figure 5 is the HAADF image of the grain boundary of the alloy prepared in Example 1 of the present invention under peak aging. The image shows that the precipitates on the grain boundary are discontinuously distributed, which has a good effect on improving the corrosion resistance of the alloy.

[0054] Example 2

[0055] Step S1: Weigh raw materials according to the weight percentages of the following components: Mg 3 wt%; Cu 2 wt%; Li 0.5 wt%; Sc 0.15 wt%; Zr 0.2 wt%; Ti 0.1 wt%; the balance is pure aluminum;

[0056] Step S2: Load pure aluminum and Al-50Cu, Al-5Zr, Al-2Sc, Al-10Ti master alloys into a graphite crucible and heat to melt; after skimming the slag, add pure magnesium, perform degassing and skimming after complete melting; then press pure Li into the melt, remove the slag and let it stand, and finally perform casting using a water-cooled copper mold under argon protection.

[0057] Step S3: Perform homogenization treatment on the obtained aluminum alloy ingot: conduct the first-stage homogenization heat treatment at 420 °C for 10 h, then raise the temperature to 510 °C at a rate of 10 °C / min for the second-stage homogenization heat treatment for 15 h, and after the heat treatment is completed, cool it in the air;

[0058] Step S3: After scalping the homogenized aluminum alloy ingot, keep it at 450 °C for 2 h; then perform hot rolling at the same temperature, control the total reduction ratio within 80% ± 4%, and the reduction ratio per pass is ~20%; sample and analyze the as-rolled sample. After testing, the physical specific gravity of the experimental alloy is 2.65 g / cm 3 ;

[0059] Step S4: Perform solution quenching heat treatment on the processed material obtained by hot rolling: conduct two-stage solution heat treatment of 505 °C / 1 h + 510 °C / 0.5 h, and immediately quench it in water after completion;

[0060] Step S5: Perform natural / artificial aging heat treatment on the quenched plate: within 1 h after completing the quenching cooling, perform artificial aging treatment within the range of 200 ± 2 °C, and the total time is 0 - 75 h.

[0061] Example 3

[0062] Step S1: Weigh the raw materials according to the following weight percentages of each component: Mg 3 wt%; Cu 1.5 wt%; Li 0.3 wt%; Si 0.3 wt%; Sc 0.15 wt%; Zr 0.2 wt%; Ti 0.1 wt%; the balance is pure aluminum;

[0063] Step S2: Load pure aluminum and Al-50Cu, Al-10Si, Al-5Zr, Al-2Sc, Al-10Ti master alloys into a graphite crucible and heat to melt; after skimming the slag, add pure magnesium, degas and skim the slag after complete melting; then press pure Li into the melt, remove the slag and let it stand, and finally cast it using a water-cooled copper mold under argon protection.

[0064] Step S3: Perform homogenization treatment on the obtained aluminum alloy ingot: conduct the first-stage homogenization heat treatment at 420 °C for 10 h, then raise the temperature to 510 °C at a rate of 10 °C / min for the second-stage homogenization heat treatment for 15 h, and after the heat treatment is completed, cool it in the air;

[0065] Step S3: After scalping the homogenized aluminum alloy ingot, keep it at 450 °C for 2 h; then perform hot rolling at the same temperature, control the total reduction ratio within 80% ± 4%, and the reduction ratio per pass is ~20%; sample and analyze the as-rolled sample. After testing, the physical specific gravity of the experimental alloy is 2.66 g / cm 3 ;

[0066] Step S4: Cold-roll the processed material obtained by hot rolling, controlling the total reduction in thickness within 50% ± 5%, and the reduction in thickness per pass is ~15%;

[0067] Step S5: Solution quenching heat treatment: Perform two-stage solution heat treatment at 505°C / 1h + 510°C / 0.5h, and immediately water quench after completion;

[0068] Step S6: Perform natural / artificial aging heat treatment on the quenched sheet: Within 1h after completion of quenching and cooling, perform artificial aging treatment within the range of 200 ± 2°C, and the total time is 0 - 75h.

[0069] Example 4

[0070] Step S1: Weigh raw materials according to the weight percentages of the following components: Mg 3wt%; Cu 2wt%; Li 0.5wt%; Sc 0.15wt%; Zr 0.2wt%; Ti 0.1wt%; the balance is pure aluminum;

[0071] Step S2: Load pure aluminum and Al-50Cu, Al-5Zr, Al-2Sc, Al-10Ti master alloys into a graphite crucible and heat to melt; after skimming the slag, add pure magnesium, degas and skim the slag after complete melting; then press pure Li into the melt, remove the slag and let it stand, and finally cast using a water-cooled copper mold under argon protection.

[0072] Step S3: Perform homogenization treatment on the obtained aluminum alloy ingot: Perform the first-stage homogenization heat treatment at 420°C for 10h, then raise the temperature to 510°C at a rate of 10°C / min for the second-stage homogenization heat treatment for 15h, and cool in air after the heat treatment is completed;

[0073] Step S3: After peeling the homogenized aluminum alloy ingot, keep it at 450°C for 2h; then perform hot extrusion at the same temperature, with an extrusion ratio of 16:1 and an extrusion speed of 1mm / s; sample and analyze the extruded sample. After testing, the physical specific gravity of the experimental alloy is 2.65 g / cm 3 ;

[0074] Step S4: Perform solution quenching heat treatment on the processed material obtained by hot extrusion: Perform two-stage solution heat treatment at 505°C / 1h + 510°C / 0.5h, and immediately water quench after completion;

[0075] Step S5: Perform natural / artificial aging heat treatment on the quenched profile: Within 1h after completion of quenching and cooling, perform artificial aging treatment within the range of 200 ± 2°C, and the total time is 0 - 75h.

[0076] Example 5

[0077] Step S1: Weigh the raw materials according to the weight percentages of the following components: Mg 3wt%; Cu 2wt%; Li 0.5wt%; Sc 0.15wt%; Zr 0.2wt%; Ti 0.1wt%; the balance is pure aluminum;

[0078] Step S2: Load pure aluminum and Al-50Cu, Al-5Zr, Al-2Sc, Al-10Ti master alloys into a graphite crucible and heat to melt; after skimming the slag, add pure magnesium, degas and skim the slag after complete melting; then press pure Li into the melt, remove the slag and let it stand, and finally cast using a water-cooled copper mold under argon protection.

[0079] Step S3: Perform homogenization treatment on the obtained aluminum alloy ingot: conduct the first-stage homogenization heat treatment at 420 °C for 10 h, then raise the temperature to 508 °C at a rate of 10 °C / min for the second-stage homogenization heat treatment for 15 h, and cool in air after the heat treatment ends;

[0080] Step S3: After skimming the skin of the homogenized aluminum alloy ingot, keep it warm at 450 °C for 2 h; then perform hot rolling at the same temperature, control the total reduction in thickness within 80% ± 4%, and the reduction in thickness per pass is ~20%; sample and analyze the as-rolled sample. After testing, the physical specific gravity of the experimental alloy is 2.65 g / cm 3 ;

[0081] Step S4: Perform solution quenching heat treatment on the processed material obtained by hot rolling: conduct two-stage solution heat treatment of 505 °C / 1 h + 510 °C / 0.5 h, and immediately water quench after completion;

[0082] Step S5: Perform natural + artificial aging heat treatment on the quenched profile: after completion of quenching and cooling, conduct natural aging at room temperature for 48 h, and then conduct artificial aging at 200 °C for 24 h.

[0083] Example 6

[0084] Step S1: Weigh the raw materials according to the weight percentages of the following components: Mg 3wt%; Cu 2wt%; Li 0.5wt%; Si 0.2wt%; Sc 0.15wt%; Zr 0.2wt%; Ti 0.1wt%; the balance is pure aluminum;

[0085] Step S2: Load pure aluminum and Al-50Cu, Al-10Si, Al-5Zr, Al-2Sc, Al-10Ti master alloys into a graphite crucible and heat to melt; after skimming the slag, add pure magnesium, degas and skim the slag after complete melting; then press pure Li into the melt, remove the slag and let it stand, and finally cast using a water-cooled copper mold under argon protection.

[0086] Step S3: Homogenize the obtained aluminum alloy ingot: conduct the first-stage homogenization heat treatment at 420 °C for 10 h, then raise the temperature to 510 °C at a rate of 10 °C / min for the second-stage homogenization heat treatment for 15 h, and cool in air after the heat treatment ends;

[0087] Step S3: After skimming the homogenized aluminum alloy ingot, hold it at 450 °C for 2 h; then conduct hot extrusion at the same temperature, with an extrusion ratio of 16:1 and an extrusion speed of 1 mm / s; sample and analyze the extruded sample. After testing, the physical specific gravity of the experimental alloy is 2.65 g / cm 3 ;

[0088] Step S4: Conduct solution quenching heat treatment on the processed material obtained by hot extrusion: conduct a two-stage solution heat treatment of 505 °C / 1 h + 510 °C / 0.5 h, and immediately quench in water after completion;

[0089] Step S5: Conduct natural + artificial aging heat treatment on the quenched profile: after completing quenching and cooling, conduct natural aging at room temperature for 48 h, and then conduct artificial aging at 200 °C for 24 h.

[0090] The aluminum alloy materials with different compositions in the above embodiments can also be prepared by other methods such as powder metallurgy and additive printing.

Claims

1. A cross-series lightweight high-strength corrosion-resistant aluminum alloy, characterized in that: The alloy composition breaks the existing aluminum alloy composition system and includes the following alloy elements and weight percentage contents: Mg: 2-3.5wt%, Cu: 1-2wt%, Li: 0.3-0.8wt%, Si: 0-0.5wt%, Mg / Cu weight ratio = 1.5-2 and at least two of the micro-alloying elements of Zr, Hf, Ti, V, Nb, Y, Sc or Er with a total content not exceeding 1wt%, and the rest are Al and unavoidable impurities; the specific gravity of the aluminum alloy is 2.64-2.67g / cm 3 , tensile strength 430~460MPa, elongation>12%, strength-ductility product>5.5GPa%, stress corrosion sensitivity coefficient ≤5%.

2. The cross-series differential lightweight high-strength corrosion-resistant aluminum alloy according to claim 1, characterized in that: The alloy composition design breaks the existing 2XXX, 5XXX, 6XXX, 8XXX aluminum alloy composition series, and obtains a sufficient amount of precipitation of the main strengthening phase GPB zone by adding the main elements Mg and Cu; the addition of elements Li and Si is not only beneficial to reducing the specific gravity of the alloy, but also can promote the precipitation of GPB. At the same time, adding Li and Si can significantly promote the precipitation of GPB and significantly increase the amount of intracrystalline precipitation of GPB. In addition, Si can be dissolved into the S phase, and Li can cover the S phase at the interface. Both are beneficial to reducing the free energy and electrode potential of the S phase, improving the thermodynamic and chemical stability, and can delay its The coarsening rate can also improve the distribution state of the grain boundary S phase under the peak aging state, that is, the common continuous network distribution along the grain boundary is improved to a discontinuous distribution, so that the aluminum alloy can achieve good corrosion resistance while obtaining high strength at the peak aging; at least two of the microalloying elements Zr, Hf, Ti, V, Nb, Y, Sc or Er are added to form a composite structure L12 phase, and finally the aluminum alloy has co-precipitation strengthening of multiple nanophases of different sizes such as GPB, S, and L12; wherein GPB is the main strengthening phase, and is highly coherent with the matrix, with a size of 20 to 50 nm and a number density of 10 16 / m 2 ; L12 phase and S phase are secondary strengthening phases, coherent or semi-coherent with the matrix, with a size of 5 to 20 nm and a number density of 10 14 / m 2 .

3. The cross-series differential lightweight high-strength corrosion-resistant aluminum alloy according to claim 1 or 2, characterized in that: The total amount of addition of all the alloying elements is <7 wt%.

4. A method for preparing a cross-series differential lightweight high-strength corrosion-resistant aluminum alloy as described in any one of claims 1 to 3, characterized in that: The steps include: Step S1: Smelting to obtain an aluminum alloy ingot; Step S2: homogenizing the obtained aluminum alloy ingot; Step S3: preheating / keeping the homogenized aluminum alloy ingot after peeling; Step S4: hot-deforming the aluminum alloy ingot after heat preservation into a desired processed material / pre-processed material by one or more hot-deforming processing methods selected from extrusion, rolling, drawing and forging; Step S5: optionally, the pre-processed material is subjected to re-annealing treatment, and then subjected to cold deformation processing to form the required processed material; Step S6: performing solution quenching heat treatment and natural / artificial aging heat treatment on the processed material obtained in step S4 or step S5.

5. The preparation method according to claim 4, characterized in that: In step S1, an ingot casting method is used to manufacture an ingot; pure aluminum and various master alloys are placed in a graphite crucible and heated to melt; after slag removal, pure magnesium is added, and after complete melting, degassing and slag removal are performed; pure Li is then pressed into the melt, and after slag removal, the melt is allowed to stand, and finally, casting is performed using a water-cooled copper mold under argon protection.

6. The preparation method according to claim 4, characterized in that: In step S2, the homogenization treatment is performed as follows: a single-stage, double-stage or multi-stage homogenization heat treatment is performed in the range of 350°C to 520°C for a total time of 12 to 72 hours.

7. The preparation method according to claim 4, characterized in that: In steps S3 and S4, the insulation temperature and the heat deformation temperature are kept consistent: the insulation temperature and each heat deformation processing temperature and the reheating temperature are 370-460°C, and the processing time is 1-5h.

8. The preparation method according to claim 4, characterized in that: In step S6, the solution heat treatment system is: single-stage, double-stage or multi-stage solution heat treatment is performed at a temperature range of 480 to 520° C. for a total time of 0.5 to 5 hours.

9. The preparation method according to claim 4, characterized in that: In step S6, the natural / artificial aging heat treatment is performed by one of the following methods: (1) Within 1 hour after quenching and cooling, artificial aging treatment is carried out at 70-300℃, with a total time of 3-100 hours; (2) After quenching and cooling, a combination of natural aging and artificial aging is used, with the artificial aging temperature being 70 to 300°C and the total time being 3 to 100 hours.

10. The preparation method according to claim 4, characterized in that: The preparation method is replaced by powder metallurgy or additive printing.

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