High-strength high-thermal-stability Al-Cu-Mg-Si alloy and preparation method thereof

Abstract

The application provides a high-strength and high-thermal-stability Al-Cu-Mg-Si alloy and a preparation method thereof, and belongs to the technical field of aluminum alloys.The chemical composition of the Al-Cu-Mg-Si alloy according to the application and the mass percentage are as follows: Si 0.5-0.9%, Fe <=0.5%, Cu 3.9-5.0%, Mn 0.4-1.2%, Mg 0.2-0.8%, Zr 0.15-0.2%, Cr 0.1-0.2%, Ni <=0.1%, Zn <=0.25%, Ti <=0.15%, the content of single impurity <=0.05%, the total content of impurities <=0.15%, and Al is the balance.The yield strength of the Al-Cu-Mg-Si alloy according to the application is >=475 MPa, the tensile strength is >=540 MPa, the elongation after fracture is >=12%, and after exposure at 200 DEG C for 100 h, the tensile strength is >=210 MPa, the yield strength is >=188 MPa, and the exfoliation corrosion grade is EB.The aluminum alloy according to the application has improved strength and thermal stability, and the corrosion resistance and toughness still maintain a high level.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum alloy, in particular to a high-strength and high-thermal-stability Al-Cu-Mg-Si alloy and a preparation method thereof. BACKGROUND

[0002] Al-Cu-Mg-Si belongs to a typical deformable and heat-treatable strengthening aluminum alloy, and has a wide application in the field of aerospace due to its high strength, corrosion resistance, thermal stability and forgeability, and is usually used as a structural part such as a plane joint and a plane hub. With the increasing demand for lightweight and high-mechanical-property materials in the automobile industry and the aerospace industry, the high-strength mass ratio, strong corrosion resistance and low cost of aluminum alloy make it more and more widely used in the above-mentioned industries; although the use of composite materials reduces the use of aluminum alloy in the plane structure, high-strength aluminum alloy is still an important plane material.

[0003] For the Al-Cu-Mg-Si alloy, although it has the advantages of excellent formability, corrosion resistance and low cost, it mainly faces the following problems in the application of the plane structure: the matching degree of strength and toughness, corrosion resistance is insufficient, and the thermal stability needs to be improved due to the use scene. If the strength and thermal stability of the Al-Cu-Mg-Si alloy can be greatly improved without reducing the toughness and corrosion resistance, the application scene and application range of the alloy will be greatly improved, and it is expected to replace some non-critical super-high-strength steel structural parts in the aerospace industry, thereby realizing the lightweight of the aerospace. Based on this, the present application studies a high-strength and high-thermal-stability Al-Cu-Mg-Si alloy and a preparation method thereof. SUMMARY

[0004] To solve the above technical problems, the present application provides a high-strength and high-thermal-stability Al-Cu-Mg-Si alloy and a preparation method thereof.

[0005] The technical scheme of the present application is as follows:

[0006] One of the purposes of the present application is to provide a high-strength and high-thermal-stability Al-Cu-Mg-Si alloy, and the chemical composition and mass percentage of the alloy are as follows: Si 0.5-0.9%, Fe≤0.5%, Cu 3.9-5.0%, Mn 0.4-1.2%, Mg 0.2-0.8%, Zr 0.15-0.2%, Cr 0.1-0.2%, Ni≤0.1%, Zn≤0.25%, Ti≤0.15%, the content of a single impurity is≤0.05%, the total content of impurities is≤0.15%, and Al is the balance.

[0007] Further, the chemical composition and mass percentage of the alloy are as follows: Si 0.6-0.8%, Fe≤0.3%, Cu 4.4-4.8%, Mn 0.8-1.1%, Mg 0.45-0.6%, Zr 0.15-0.18%, Cr 0.1-0.15%, Ni≤0.1%, Zn≤0.2%, Ti≤0.1%, and the Cu / Mg ratio is 8-10, the Fe / Ni ratio is≤2.5, the single impurity content is≤0.05%, the total impurity content is≤0.15%, and Al is the balance.

[0008] Further, the yield strength of the Al-Cu-Mg-Si alloy is≥475 MPa, the tensile strength is≥540 MPa, and the elongation after fracture is≥12%; and after exposure at 200℃ for 100h, the tensile strength is≥210 MPa, the yield strength is≥188 MPa, and the exfoliation corrosion rating is EB.

[0009] The second object of the present application is to provide a preparation method of the high-strength and high-thermal-stability Al-Cu-Mg-Si alloy, comprising the following steps:

[0010] S1, the chemical composition range of the Al-Cu-Mg-Si alloy is preset, then the relationship between the chemical composition ratio and the performance is simulated by using the Jmatpro software, and the optimal chemical composition range of the Al-Cu-Mg-Si alloy is determined according to the matching degree of strength, toughness and corrosion resistance and thermal stability;

[0011] S2, according to the chemical composition range determined in step S1, the raw materials are melted and cast to obtain the Al-Cu-Mg-Si alloy ingot;

[0012] S3, the Al-Cu-Mg-Si alloy ingot is subjected to homogenization treatment;

[0013] S4, the Al-Cu-Mg-Si alloy ingot after homogenization treatment is sawn into aluminum rods and subjected to hot extrusion to obtain extruded profiles;

[0014] S5, the extruded profiles are subjected to solid solution treatment at a solid solution temperature, and then quenched to room temperature after the solid solution treatment is completed;

[0015] S6, the extruded profiles after the solid solution treatment and quenching treatment are subjected to tensile straightening treatment;

[0016] S7, the extruded profiles after stretching are subjected to aging treatment, and then air-cooled to room temperature to obtain the Al-Cu-Mg-Si alloy profiles.

[0017] Further, the step S2 controls the melt temperature to be ≤745℃ during smelting, and the melt temperature in the smelting furnace before the melt is transferred from the smelting furnace to the refining furnace is 740±5℃; the melt temperature reaching 700℃ is taken as the start time of the melt staying in the smelting furnace, the start time of the converter is taken as the end time of the melt staying in the smelting furnace, and the staying time of the melt in the smelting furnace is controlled to be not more than 8 hours, and if the time exceeds the specified time, the melt is re-stirred and sampled;

[0018] During the casting process, the casting water temperature is 18-23℃, the starting casting temperature is 735-745℃, the casting temperature is 685-705℃, the casting speed is 31-35mm / min, the water flow is 34-40m 3 / h, and the molten aluminum temperature at the outlet of the holding furnace is controlled to be ≤750℃ during the casting process, and the casting temperature at the hot end of the flow disc is 695±10℃.

[0019] Further, in the step S3, the homogenization treatment adopts a two-stage homogenization process, the first-stage homogenization is heated to 485±5℃ at a heating rate of 35-50℃ / h and is kept for 10-12h, and the second-stage homogenization is heated to 495±5℃ at a heating rate of 15-25℃ / h and is kept for 5-8h.

[0020] Further, in the hot extrusion of the step S4, the mold temperature is set to be 385-415℃, the holding time is 4-36h, the inner layer of the extrusion cylinder is heated to 405-435℃, the aluminum rod is kept at 370-400℃, the extrusion rod speed is 0.2-0.6mm / s, the single speed-up amount is 0.05mm / s, and the speed-up completion time is ≤3min.

[0021] Further, in the step S5, the solid solution treatment adopts a two-stage solid solution process, the first-stage initial solid solution temperature is 495±5℃, and the solid solution time is 4-6h; the second-stage strengthening solid solution temperature is 505±5℃, and the solid solution time is 6-8h.

[0022] After the solid solution treatment is completed, the quenching delay time is controlled to be ≤150s during the quenching process, and the water temperature before and after the quenching is not more than 25℃.

[0023] Further, in the step S6, the time interval from the completion of the quenching to the completion of the stretching is ≤6h.

[0024] Further, in the step S7, the aging temperature is 175-195℃, and the aging time is 12h.

[0025] Compared with the prior art, the application has the beneficial effects that:

[0026] (1) The application provides a high-strength and high-thermal-stability Al-Cu-Mg-Si alloy, from the perspective of dispersion strengthening and precipitation strengthening, by controlling the contents of Cu and Mg and adjusting the Cu / Mg ratio, the alloy generates S phase as much as possible; in addition, in order to prevent the decrease of corrosion resistance caused by too high Mg content, the application reduces the Mg content and increases the Mn content, so as to ensure the strength of the alloy while ensuring the corrosion resistance; the application also adds elements such as Cr and Zr, the Zr element can form Al3Zr to provide nucleation sites and play a role in refining grains, thereby achieving the effect of fine-grain strengthening, the Cr element forms (CrFe)Al7 and (CrMn)Al 12 compounds in aluminum, which can hinder the nucleation and growth process of recrystallization and has a certain strengthening effect on the alloy, and can also improve the toughness of the alloy and reduce the stress corrosion cracking sensitivity; at the same time, the application also controls the addition amount and ratio of Mg, Cu, Fe and Ni, controls the formation of more heat-resistant phases Al2CuMg phase and FeNiAl9 phase, and ensures that the alloy has good thermal stability, so as to ensure that the aluminum alloy has high strength and thermal stability while maintaining high corrosion resistance and toughness;

[0027] (2) The application provides a high-strength and high-thermal-stability Al-Cu-Mg-Si alloy and a preparation method thereof, by adjusting and optimizing the chemical composition of the Al-Cu-Mg-Si alloy, the strength and thermal stability are improved under the premise of ensuring toughness and corrosion resistance, the yield strength is greater than or equal to 475 MPa, the tensile strength is greater than or equal to 540 MPa, the elongation after fracture is greater than or equal to 12%, and after exposure at 200℃ for 100h, the tensile strength is greater than or equal to 210 MPa, the yield strength is greater than or equal to 188 MPa, and the exfoliation corrosion rating is EB. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description, and obviously, other drawings can also be obtained by those skilled in the art without creative labor.

[0029] Figure 1 The equilibrium phase and corresponding precipitation temperature of the Al-Cu-Mg-Si alloy in Example 1 during solidification;

[0030] Figure 2 The precipitation temperature and precipitation amount change trend diagram of the Al6Mn phase in Example 1 during solidification under different Cu element contents;

[0031] Figure 3The figure of the change trend of the precipitation temperature and the precipitation amount of the Al2Cu phase in the solidification process under different Cu element contents in the embodiment 1;

[0032] Figure 4 The metallographic structure photo of the Al-Cu-Mg-Si alloy profile prepared in the embodiment 2;

[0033] Figure 5 The transmission electron microscope photo of the Al-Cu-Mg-Si alloy in the solid solution state prepared in the embodiment 2. DETAILED DESCRIPTION

[0034] In order to make the personnel in the technical field better understand the technical solutions in the present application, the technical solutions of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by the personnel in the field without creative labor should belong to the protection scope of the present application.

[0035] Embodiment 1

[0036] In order to solve the problems of the insufficient matching degree of the strength and the toughness, the poor corrosion resistance and the poor thermal stability of the Al-Cu-Mg-Si alloy profile for the aviation, the present embodiment optimizes the types and the contents of the alloy elements by using the numerical simulation method, that is, the chemical composition range of the Al-Cu-Mg-Si alloy is set in advance, then the relationship between the chemical composition ratio and the performance is simulated by using the Jmatpro software, and the optimal chemical composition range of the Al-Cu-Mg-Si alloy is determined according to the matching degree of the strength, the toughness, the corrosion resistance and the thermal stability; the specific steps are as follows:

[0037] (1) On the basis of analyzing the role of each alloying element in the Al-Cu-Mg-Si alloy and the role of each equilibrium phase, the types of alloying elements of the alloy are adjusted, and a relatively wide chemical composition range of the Al-Cu-Mg-Si alloy is set in advance, i.e. Si 0.5-0.9%, Fe≤0.5%, Cu 3.9-5.0%, Mn 0.4-1.2%, Mg 0.2-0.8%, Zr 0.15-0.2%, Cr 0.1-0.2%, Ni≤0.1%, Zn≤0.25%, Ti≤0.15%, and the content of each impurity is ≤0.05%, and the total content of impurities is ≤0.15%, and the balance is Al; a certain chemical composition is selected from the range, such as Si 0.6%, Fe 0.2%, Cu 4.6%, Mn 1.0%, Mg 0.5%, Zr 0.16%, Cr 0.15%, Ni 0.1%, Zn 0.2%, and Ti 0.1%, the Jmatpro software is used for simulation, the initial temperature is set to 700°C, and the end temperature is set to 100°C, the equilibrium phase and the corresponding precipitation temperature of the Al-Cu-Mg-Si alloy during the solidification process are obtained, and the performance of the Al-Cu-Mg-Si alloy is obtained.

[0038] (2) On the basis of the above ratio, other elements are fixed, only the Cu element is adjusted, the content of the Cu element is taken as different values within 3.9%-5.0%, the Jmatpro software is used for simulation again, the equilibrium phase and the corresponding precipitation temperature of the alloy with different Cu element contents are studied, and the performance of the alloy with different Cu element contents is obtained; in addition, one or more equilibrium phases can be extracted from the simulation results to study the change trend of the equilibrium phase under different Cu element contents;

[0039] (3) Repeat step (2), adjust other main alloying elements such as Mg and Mn in turn, study the equilibrium phase and the corresponding precipitation temperature of the alloy under different contents of other main elements, and obtain the corresponding performance;

[0040] (4) Analyze the relationship between the obtained different chemical composition ratios and the performance, determine the appropriate chemical composition ratio according to the change of each phase and the performance change trend, and conduct several groups of tests according to the determined chemical composition ratio, and sample detection of mechanical properties, corrosion resistance and thermal stability, and determine the optimal chemical composition range of the Al-Cu-Mg-Si alloy according to the matching degree of strength, toughness, corrosion resistance and thermal stability.

[0041] Reference Figures 1-3 The simulation results of the above embodiment 1 are described, Figure 1 the equilibrium phase and the corresponding precipitation temperature of the Al-Cu-Mg-Si alloy during the solidification process, Figure 2Figures showing the change trend of the precipitation temperature and the precipitation amount of the Al6Mn phase in the solidification process under different Cu element contents, Figure 3 Figures showing the change trend of the precipitation temperature and the precipitation amount of the Al2Cu phase in the solidification process under different Cu element contents. Figure 1 From the above, the equilibrium phase types that can be precipitated in the solidification process of the Al-Cu-Mg-Si alloy can be obtained, and the corresponding precipitation temperatures of the equilibrium phases are obtained. On this basis, the equilibrium phases that mainly affect the performance of the Al-Cu-Mg-Si alloy can be analyzed, and the main equilibrium phases, such as the Al6Mn phase and the Al2Cu phase, can be further studied. Figure 2 Figure 3 From the above, the change trend of the precipitation temperature and the precipitation amount of the Al6Mn phase and the Al2Cu phase in the solidification process under different Cu element contents can be obtained. Specifically, from the above, Figure 2 It can be seen that when the Cu content continuously increases, with the continuous decrease of the temperature, the change trend of the Al6Mn precipitated phase in the non-equilibrium solidification process presents a trend of first increasing, then decreasing, and finally instantaneously increasing to a maximum value and then tending to be balanced. There is a non-precipitation zone between 610℃ and 140℃. When the Cu content is 3.9-5.0%, the change trend is consistent, and there is a rapid increase region of the Al6Mn precipitated phase between 140℃ and 100℃. Figure 3 It can be seen that when the Cu content continuously increases, with the continuous decrease of the temperature, the change trend of the Al2Cu precipitated phase in the non-equilibrium solidification process presents a continuous increase state, and the increase speed presents a state of first fast and then slow. Finally, it instantaneously increases to a maximum value and then tends to be balanced. When the Cu content is in the interval of 3.9-5.0%, Al2Cu is precipitated in the interval of 520-100℃, and the precipitation rate is basically consistent. However, with the increase of the Cu content from 3.9% to 4.8%, the Al2Cu precipitation amount also gradually increases. When the Cu content is 5.0%, the Al2Cu precipitation amount slightly decreases.

[0042] In addition, the change trend of the mechanical properties under different Cu element contents can also be obtained by using the Jmatpro software. When the Mg content is constant, with the increase of the Cu content in the range of 3.9-5.0%, the tensile strength of the alloy increases, and the elongation rate does not change significantly. However, if the amount of Cu element is too high, it will promote the precipitation of Al2Cu and AlCuMgMn phases, thereby increasing the potential difference between the matrix and the second phase, and leading to the decrease of the corrosion resistance. In order to obtain the alloy element range with good strength, toughness, corrosion resistance and thermal stability, further pilot tests are carried out to obtain the actual mechanical properties, corrosion resistance and thermal stability data, and a more optimal alloy element range is obtained.

[0043] ​This embodiment takes the variation of Cu element content as an example. Based on the above simulation, several representative alloy ranges are selected, as shown in Table 1 below. The corresponding alloys are prepared through pilot-scale experiments using the same casting, homogenization, and extrusion processes, and their mechanical properties, corrosion resistance, and thermal stability are obtained, as shown in Table 2.

[0044] Table 1

[0045]

[0046]

[0047] Table 2

[0048]

[0049] The experimental results and simulation results show a consistent trend. Although the strength increases with increasing Cu content, the corrosion resistance decreases significantly. Therefore, the preferred range for Cu content is 4.4% to 4.8%.

[0050] Based on the technical problem to be solved by this invention, this embodiment, in analyzing the above numerical simulation results, namely the precipitation amount and performance change trend of the equilibrium phase under different chemical compositions, mainly considers increasing the content of the S phase (Al2CuMg) as much as possible to ensure its high strength and toughness, while reducing the content of precipitated phases such as Al2Cu and AlCuMnSi to reduce the potential difference between the second phase and the matrix, thereby ensuring its corrosion resistance; at the same time, the changes of the Al3Zr precipitated phase are analyzed, with the aim of utilizing the Al3Zr precipitated phase to refine the grain structure and achieve the effect of fine grain strengthening; and (CrFe)Al7 and (CrMn)Al are also analyzed. 12 The precipitation of intermetallic compounds, such as (CrFe)Al7 and (CrMn)Al, is utilized to achieve the desired effect. 12 This hinders the nucleation and growth processes of recrystallization, improves the microstructure, enhances the toughness of the alloy, and reduces the susceptibility to stress corrosion cracking. In addition, this embodiment also needs to obtain good thermal stability. The main heat-resistant phases in this type of alloy are S(Al2CuMg) phase and FeNiAl9 phase. In order to obtain high thermal stability, it is necessary to control the formation of S(Al2CuMg) phase and FeNiAl9 phase.

[0051] This embodiment analyzes the numerical simulation results and the roles of major alloying elements in the Al-Cu-Mg-Si alloy. Combined with pilot-scale experimental data, the chemical composition range of the alloy is determined, specifically:

[0052] Cu element as an important alloying element, the effect on strength, toughness is mainly related to the strengthening phase Al2Cu, Al2CuMg, in addition, the content of Cu element on the size of Vickers hardness is more obvious. When the Cu / Mg ratio is constant, the tensile strength and hardness of the alloy increase significantly with the increase of Cu, Mg content, the elongation decreases slightly; when the Mg content is constant, the tensile strength and hardness of the alloy increase significantly with the increase of Cu / Mg, the elongation has no obvious change, but the amount of Cu element is too high, which will promote the precipitation of Al2Cu and AlCuMgMn phase, thereby increasing the potential difference between the matrix and the second phase, resulting in the decrease of corrosion resistance. Combined with the simulation results and the test data of pilot experiment, the range of Cu element is selected as 3.9-5.0%, preferably 4.4-4.8%; in addition, the Cu / Mg ratio needs to be controlled at 8.0-10.0 to promote the precipitation of Al2CuMg and reduce the precipitation of Al2Cu and AlCuMgMn;

[0053] Mg element as an important strengthening element, is particularly significant for improving the aging mechanical properties of Al-Cu-Mg alloy, but at the same time it will reduce the elongation of the alloy. Mg element has a more obvious effect on the as-cast structure, when the Mg, Zn content is too high, it will form more dendritic structure in the matrix, which is difficult to eliminate by subsequent homogenization annealing. At the same time, Mg element as an important component of strengthening phase has a certain influence on the mechanical properties and electrical conductivity of as-cast aluminum alloy. From the perspective of dispersion strengthening and precipitation strengthening, it is necessary to make the alloy generate strengthening phase S as much as possible to improve its aging strength. However, Mg≥0.6% will promote the formation of residual crystalline phase and Cu-rich aging precipitates, increase the width of PFZ, and increase the potential difference between the cathode and the anode, accelerating the corrosion. Combined with the simulation results of this embodiment, with the increase of Mg element content, the mechanical properties of Al-Cu-Mg-Si alloy show a trend of first increasing and then decreasing, therefore we use Mn element to supplement part of the strengthening effect, which can reduce the content of Mg element, so as to ensure the toughness and corrosion resistance of the alloy; in addition, the main heat-resistant phase in this kind of alloy is S(Al2CuMg) phase, in order to obtain good thermal stability, the Mg content cannot be too low, and the appropriate increase of Mg content makes the alloy composition fall within the α(Al)+S+Al2Cu three-phase region in the Al-Cu-Mg ternary equilibrium diagram, and as much as possible to ensure the S(Al2CuMg) phase. Therefore, the content of Mg element is selected as 0.2-0.8%, the content of Mn element is selected as 0.4-1.2%, preferably, the content of Mg element is selected as 0.46-0.6%, and the content of Mn element is selected as 0.8-1.1%;

[0054] Fe, Si impurity elements are generally unavoidable, and are easy to form coarse, insoluble phases such as Al7Cu2Fe, Mg2Si, etc. Especially in the alloy with high Cu element, Fe, Si generally exist in these two forms, and a part of strengthening elements are consumed in the forming process of these two phases, so Fe, Si have great influence on the strength, plasticity, toughness, electrical conductivity, quenching sensitivity of the alloy, especially on the strength and plasticity of large wall thickness. However, Si element can promote the formation of Q phase in the Al-Cu-Mg-Si alloy. In combination with the actual production cost, numerical simulation results and pilot test data, the selected Fe is ≤0.5%, the Si content is 0.5-0.9%, the preferred Fe is ≤0.3%, and the Si content is 0.6-0.8%;

[0055] In the alloy, Fe and Ni have good influence on the heat resistance of the alloy, but the addition of iron and nickel alone will reduce the heat resistance of the alloy, and the appropriate addition of nickel can prevent the formation of Cu2FeAl2, CuFeAl3 phases, but excessive addition will form AlCu x Ni y By controlling Fe / Ni≤2.5, the FeNiAl9 phase with good heat resistance is finally formed by combining Fe and Ni, so that a large amount of S(Al2CuMg) phase can be formed in Cu in the alloy, thereby ensuring that the alloy has good thermal stability;

[0056] Ti is a commonly used additive element in aluminum alloy, which is added in the form of Al-Ti or Al-Ti-B intermediate alloy. Ti forms TiAl2 phase with Al, becomes a non-spontaneous core during crystallization, and plays a role in refining the casting structure;

[0057] Zr element and Cr element are also added in the embodiment, wherein the Zr element can form Al3Zr to provide nucleation sites and play a role in refining the grain, but if the Zr content is too high, coarse Al3Zr primary phase will be precipitated, thereby reducing the Zr content dissolved in the matrix during alloy solidification, and thereby reducing the beneficial effect of Zr. In combination with the numerical simulation results, the selected range of Zr element is 0.15-0.2%, and the preferred range is 0.15-0.18%. The Cr element forms (CrFe)Al7 and (CrMn)Al 12 compounds in aluminum, which can hinder the nucleation and growth process of recrystallization, has a certain strengthening effect on the alloy, and can also improve the toughness of the alloy and reduce the stress corrosion cracking sensitivity. However, the calculation results show that the addition amount should not exceed 0.35%, and if the addition amount exceeds this content, coarse Cr-containing compounds will be formed, which will reduce the plasticity and formability of the alloy. Therefore, the selected range of Cr element is 0.1-0.2%, and the preferred range is 0.1-0.15%.

[0058] By analyzing the above numerical simulation results, and analyzing the role of each main alloying element in the Al-Cu-Mg-Si alloy, the chemical composition range of the Al-Cu-Mg-Si alloy is obtained: Si 0.5-0.9%, Fe≤0.5%, Cu 3.9-5.0%, Mn 0.4-1.2%, Mg 0.2-0.8%, Zr 0.15-0.2%, Cr 0.1-0.2%, Ni≤0.1%, Zn≤0.25%, Ti≤0.15%, single impurity content≤0.05%, total impurity content≤0.15%, and Al as the balance; preferably Si 0.6-0.8%, Fe≤0.3%, Cu 4.4-4.8%, Mn 0.8-1.1%, Mg 0.45-0.6%, Zr 0.15-0.18%, Cr 0.1-0.15%, Ni≤0.1%, Zn≤0.2%, Ti≤0.1%, single impurity content≤0.05%, total impurity content≤0.15%, and Al as the balance.

[0059] The simulation results of chemical composition-performance obtained by numerical simulation calculation in the embodiment can save a large amount of trial and error time and cost in the early stage of composition design. The Al-Cu-Mg-Si alloy with high strength and high thermal stability is obtained by optimizing and adjusting the chemical composition of the alloy. The alloy has high strength and high thermal stability while ensuring toughness and corrosion resistance. The yield strength of the alloy is≥475 MPa, the tensile strength is≥540 MPa, and the elongation after fracture is≥12%. After exposure at 200℃ for 100h, the tensile strength is≥210 MPa, the yield strength is≥188 MPa, and the exfoliation corrosion rating is EB.

[0060] Embodiment 2

[0061] On the basis of the chemical composition range of the Al-Cu-Mg-Si alloy determined in embodiment 1, the Al-Cu-Mg-Si alloy profile is prepared in the embodiment, and performance detection is carried out.

[0062] The chemical composition of the Al-Cu-Mg-Si alloy in the embodiment is: Si 0.6%, Fe 0.3%, Cu 4.4%, Mn 0.8%, Mg 0.45%, Zr 0.15%, Cr 0.1%, Ni 0.08%, Zn 0.17%, Ti 0.09%, and the balance is Al.

[0063] The preparation method of the Al-Cu-Mg-Si alloy in the embodiment comprises the following steps:

[0064] S1, according to the chemical composition of Al-Cu-Mg-Si alloy ratio of pure Al, Cu plate, Mg ingot, Al-Si intermediate alloy, Al-Mn intermediate alloy, Al-Zr intermediate alloy, Al-Cr, Al-Ti intermediate alloy and Al-Ni as raw material;

[0065] S2, the above raw materials are smelted and cast, wherein the furnace chamber of the smelting furnace is set to a temperature setting value ≤ 1060℃, and the electromagnetic stirring is started when the smelting temperature of the furnace charge reaches 700℃. After the raw materials in the smelting furnace are completely melted, the melt temperature is measured and slagging, Mg ingot adding, stirring, slagging and sampling are carried out. The melt stays in the smelting furnace for 5h to obtain an aluminum alloy smelting liquid. Then the melt is transferred from the smelting furnace to the refining furnace. At this time, the melt temperature in the smelting furnace is 744℃. After refining is completed, casting is carried out under the following casting process parameters: casting water temperature is 19℃, casting temperature is 700℃, casting speed is 33mm / min, water flow is 37 / m3 / h, and flow disc hot end casting temperature is 697℃. A large-size ingot with a diameter of φ600mm and a length of 12m is obtained.

[0066] S3, the Al-Cu-Mg-Si alloy ingot is subjected to homogenization treatment. The homogenization treatment adopts a two-stage homogenization process, and the stacking direction of the ingot is consistent with the circulating air direction of the soaking furnace. Specifically, the first-stage homogenization is heated to 485℃ at a heating rate of 40℃ / h and kept for 12h. The second-stage homogenization is heated to 495℃ at a heating rate of 20℃ / h and kept for 5h, and then air-cooled to room temperature after being discharged. The two-stage homogenization treatment can make the intracrystalline coarse precipitates dissolve more thoroughly, and the size and quantity of intracrystalline eutectic phase are further reduced, so that the structure is more uniform, and the performance of the material is improved. The first-stage homogenization is mainly used to eliminate segregation and prevent local overburning. The second-stage homogenization can fully eliminate composition segregation and maximize the dissolution of micron-sized phases.

[0067] S4, the Al-Cu-Mg-Si alloy ingot after homogenization treatment is sawn into aluminum rods, and hot extrusion is carried out to obtain an extruded profile. In the hot extrusion, the extrusion cylinder diameter is 600mm, the extrusion cylinder setting temperature is 420℃, the temperature of the inner layer 1-4 zone is controlled at 410-421℃, the die heat preservation temperature is 400℃, the heat preservation time is 5h, the aluminum rod heat preservation temperature is 380℃, the extrusion rod speed is 0.4mm / s, the single speed-up amount is 0.05mm / s, and the speed-up completion time is 159s. An extruded profile with a wall thickness of 150mm is obtained by extrusion.

[0068] S5. The extruded profile is solution treated at the solution temperature, and then quenched to room temperature after the solution treatment. The solution treatment adopts a two-stage solution treatment process. The initial solution temperature of the first stage is 495℃ and the solution time is 4h. The strengthening solution temperature of the second stage is 505℃ and the solution time is 7h. After the solution treatment, it is water quenched to room temperature. The quenching delay time is ≤85s. The water temperature before and after the solution quenching does not exceed 25℃.

[0069] S6. The extruded profiles after solution treatment and quenching are subjected to stretching and straightening treatment. The stretching rate is set to 2.0%, the stretching speed is 120 mm / s, the clamping force is 100 t, and the time interval between the completion of quenching and the completion of stretching is ≤6 h.

[0070] S7. The stretched extruded profile is subjected to aging treatment at a temperature of 180℃ for 12 hours, followed by air cooling to room temperature to obtain Al-Cu-Mg-Si alloy profile.

[0071] The Al-Cu-Mg-Si alloy profile tested to have a yield strength of 482 MPa, a tensile strength of 545 MPa, and an elongation after fracture of 12.5%. After being exposed to 200°C for 100 hours, the profile had a tensile strength of 222 MPa, a yield strength of 189 MPa, and an exfoliation corrosion rating of EB.

[0072] In addition, metallographic analysis was performed on samples of the Al-Cu-Mg-Si alloy profiles prepared in this embodiment, such as... Figure 4 As shown, from Figure 4 It can be seen that the alloy has a uniform grain structure and no large-sized second phase, voids, or microporous defects were found.

[0073] In addition, samples of the Al-Cu-Mg-Si alloy prepared in this embodiment were taken in the solid solution state and examined using transmission electron microscopy, such as... Figure 5 As shown, from Figure 5 As can be seen, the S phase is fully dissolved in the Al matrix in the solid state. At the same time, except for a small number of large-sized S phases that are not re-dissolved, the rest of the second phases are also fully dissolved into the Al matrix within the grains and at the grain boundaries. This lays a good foundation for subsequent aging strengthening and overall material development.

[0074] Example 3

[0075] The chemical composition of the Al-Cu-Mg-Si alloy in this embodiment is as follows: Si 0.6%, Fe 0.3%, Cu 4.4%, Mn 0.8%, Mg 0.45%, Zr 0.15%, Cr 0.1%, Ni 0.08%, Zn 0.17%, Ti 0.09%, with the balance being Al.

[0076] The preparation method of the Al-Cu-Mg-Si alloy in the embodiment comprises the following steps:

[0077] S1, pure Al, Cu plate, Mg ingot, Al-Si intermediate alloy, Al-Mn intermediate alloy, Al-Zr intermediate alloy, Al-Cr, Al-Ti intermediate alloy and Al-Ni are weighed as raw materials according to the chemical component proportion of the Al-Cu-Mg-Si alloy;

[0078] S2, the raw materials are subjected to melting and casting, wherein the temperature setting value of the hearth in the melting furnace is ≤1060℃, after the raw materials in the melting furnace are completely melted, the melt temperature is measured, and slagging, Mg ingot adding, stirring, slagging and sampling are performed, the melt stays in the melting furnace for 5h, and an aluminum alloy melting liquid is obtained; then the melt is transferred from the melting furnace to a refining furnace, at this time, the melt temperature in the melting furnace is 745℃, after the refining is completed, casting is performed under the casting process parameters that the water temperature is 22℃, the starting casting temperature is 739℃, the casting temperature is 698℃, the casting speed is 31mm / min, the water flow is 36 / m 3 / h and the flow disc hot end casting temperature is 700℃, and a large-size ingot with a diameter of φ600mm and a length of 11.7m is obtained;

[0079] S3, the Al-Cu-Mg-Si alloy ingot is subjected to homogenization treatment, the homogenization treatment adopts a two-stage homogenization process, and the stacking direction of the ingot is consistent with the circulating air direction of the soaking furnace; specifically, the first-stage homogenization is heated to 485℃ at a heating rate of 40℃ / h and is kept for 11h; the second-stage homogenization is heated to 494℃ at a heating rate of 20℃ / h and is kept for 6h, and is air-cooled to room temperature after being discharged; the two-stage homogenization treatment can make the intracrystalline coarse precipitates more completely dissolved, the size and quantity of the intracrystalline eutectic phase are further reduced, so that the structure is more uniform, and the performance of the material is further improved, wherein the first-stage homogenization is mainly used for eliminating segregation and preventing local overburning, and the second-stage homogenization can sufficiently eliminate composition segregation and maximally dissolve micron-sized phases;

[0080] S4, the Al-Cu-Mg-Si alloy ingot after the homogenization treatment is sawn into aluminum rods, and is subjected to hot extrusion, and an extruded profile is obtained; in the hot extrusion, the extrusion cylinder has a diameter of 600mm, the set temperature of the extrusion cylinder is 420℃, the temperature of the inner layer 1-4 is controlled to be 408-423℃, the die heat preservation temperature is 385℃, the heat preservation time is 18h, the aluminum rod heat preservation temperature is 400℃, the extrusion rod speed is 0.4mm / s, the single speed-up amount is 0.05mm / s, the speed-up completion time is 128s, and an extruded profile with a wall thickness of 150mm is obtained through the extrusion;

[0081] S5, solution treatment of the extruded profile at a solution temperature, and quenching to room temperature after the solution treatment is completed; the solution treatment adopts a two-stage solution process, the initial solution temperature of the first stage is 495℃, and the solution time is 5h; the strengthening solution temperature of the second stage is 505℃, and the solution time is 8h; after the solution treatment is completed, water quenching to room temperature, and the quenching delay time is ≤93s, and the water temperature before and after the solution quenching is not more than 25℃;

[0082] S6, the extruded profile after the solution treatment and the quenching treatment is subjected to a tensile straightening treatment, the tensile rate is set to 2.0%, the tensile speed is 120mm / s, the clamping force is 100t, and the time interval between the completion of the quenching and the completion of the tensile is ≤6h;

[0083] S7, the extruded profile after the tensile is subjected to an aging treatment, the aging treatment temperature is 190℃, the holding time is 10h, and then air cooling to room temperature, to obtain an Al-Cu-Mg-Si alloy profile.

[0084] It is detected that the yield strength of the above-mentioned Al-Cu-Mg-Si alloy profile is 490MPa, the tensile strength is 542MPa, and the elongation after fracture is 12.0%, and after the profile is exposed at 200℃ for 100h, the tensile strength is 222MPa, the yield strength is 191MPa, and the exfoliation corrosion grade is EB.

[0085] Example 4

[0086] The difference between this embodiment and Example 2 is that the chemical composition of the Al-Cu-Mg-Si alloy in this embodiment is: Si 0.8%, Fe 0.3%, Cu 4.8%, Mn 1.1%, Mg 0.6%, Zr 0.18%, Cr 0.15%, Ni 0.08%, Zn 0.20%, Ti 0.09%, and the balance is Al.

[0087] The preparation method of the Al-Cu-Mg-Si alloy in this embodiment includes the following steps:

[0088] S1, according to the chemical composition ratio of the Al-Cu-Mg-Si alloy, pure Al, Cu plate, Mg ingot, Al-Si intermediate alloy, Al-Mn intermediate alloy, Al-Zr intermediate alloy, Al-Cr, Al-Ti intermediate alloy and Al-Ni are weighed as raw materials;

[0089] S2, the raw materials are smelted and cast, wherein the temperature setting value of the hearth of the smelting furnace is ≤1060℃, after the raw materials in the smelting furnace are completely melted, the melt temperature is measured and slagging, Mg ingot adding, stirring, slagging and sampling are performed, the melt stays in the smelting furnace for 5h, and an aluminum alloy smelting liquid is obtained; then the melt is transferred from the smelting furnace to a refining furnace, at this time, the melt temperature in the smelting furnace is 745℃, after the refining is completed, casting is performed under the casting process parameters that the water temperature is 22℃, the starting casting temperature is 739℃, the casting temperature is 698℃, the casting speed is 31mm / min, the water flow is 36 / m 3 / h, and the flow disc hot end casting temperature is 700℃, to obtain a large-size ingot with a diameter of φ600mm and a length of 12.0m;

[0090] S3, the Al-Cu-Mg-Si alloy ingot is subjected to homogenization treatment, the homogenization treatment adopts a two-stage homogenization process, and the stacking direction of the ingot is consistent with the circulating air direction of the soaking furnace; specifically, the first-stage homogenization is heated to 485℃ at a heating rate of 40℃ / h and is kept for 11h; the second-stage homogenization is heated to 494℃ at a heating rate of 20℃ / h and is kept for 6h, and is air-cooled to room temperature after being discharged; the two-stage homogenization treatment adopted in this embodiment can make the intracrystalline coarse precipitates more completely dissolved, the size and quantity of the intracrystalline eutectic phase are further reduced, so that the structure is more uniform, and the performance of the material is further improved, wherein the first-stage homogenization is mainly used to eliminate segregation and prevent local overburning, and the second-stage homogenization can fully eliminate composition segregation and maximally dissolve micron-sized phases;

[0091] S4, the Al-Cu-Mg-Si alloy ingot after the homogenization treatment is sawn into aluminum rods, and is subjected to hot extrusion to obtain an extruded profile; in the hot extrusion, the extrusion cylinder has a diameter of 600mm, the set temperature of the extrusion cylinder is 420℃, the temperature of the inner layer 1-4 is controlled to be 408-423℃, the die heat preservation temperature is 415℃, the heat preservation time is 36h, the aluminum rod heat preservation temperature is 435℃, the extrusion rod speed is 0.4mm / s, the single speed-up amount is 0.05mm / s, the speed-up completion time is 130s, and an extruded profile with a wall thickness of 150mm is obtained through the extrusion;

[0092] S5, the extruded profile is subjected to solid solution treatment at a solid solution temperature, and is quenched to room temperature after the solid solution treatment is completed; the solid solution treatment adopts a two-stage solid solution process, the initial solid solution temperature of the first stage is 495℃, and the solid solution time is 5h; the strengthening solid solution temperature of the second stage is 505℃, and the solid solution time is 8h; after the solid solution treatment is completed, the water quenching is performed to room temperature, the quenching delay time is ≤93s, and the water temperature before and after the solid solution quenching does not exceed 25℃;

[0093] S6, the extruded profile after the solid solution treatment and quenching treatment is subjected to a tension straightening treatment, the tension rate is set to 2.0%, the tension speed is 120 mm / s, the clamping force is 100 t, and the time interval between the completion of quenching and the completion of tension is ≤6 h;

[0094] S7, the extruded profile after the tension is subjected to an aging treatment, the aging treatment temperature is 190℃, the holding time is 10 h, and then air cooling to room temperature to obtain the Al-Cu-Mg-Si alloy profile.

[0095] It is detected that the yield strength of the above-mentioned Al-Cu-Mg-Si alloy profile is 485 MPa, the tensile strength is 546 MPa, the elongation after fracture is 12.5%, after the profile is exposed at 200℃ for 100 h, the tensile strength is 219 MPa, the yield strength is 193 MPa, and the exfoliation corrosion rating is EB.

[0096] Comparative Example 1

[0097] The difference between the present comparative example and Example 2 is that the chemical composition of the Al-Cu-Mg-Si alloy in the present comparative example is: Si 0.9%, Fe 0.3%, Cu 5.2%, Mn 1.2%, Mg 0.3%, Cr 0.1%, Zn 0.17%, Ti 0.09%, and the balance is Al.

[0098] It is detected that the yield strength of the above-mentioned Al-Cu-Mg-Si alloy profile is 505 MPa, the tensile strength is 578 MPa, the elongation after fracture is 12%, after the profile is exposed at 200℃ for 100 h, the tensile strength is 220 MPa, the yield strength is 198 MPa, and the exfoliation corrosion rating is ED.

[0099] It should be noted that the parts not mentioned in the present application can be realized by using or referring to the existing technology.

[0100] Of course, the above description is not a limitation of the present application, and the present application is not limited to the above examples, and the changes, modifications, additions or replacements made by the person skilled in the art within the essential scope of the present application should also belong to the protection scope of the present application.

Claims

1. A method of producing a high-strength high-thermal-stability Al-Cu-Mg-Si alloy, characterized by, The method comprises the steps of: S1, presetting the chemical composition range of the Al-Cu-Mg-Si alloy, and then simulating the relationship between the chemical composition ratio and the performance by using the Jmatpro software, and determining the optimal chemical composition range of the Al-Cu-Mg-Si alloy according to the matching degree of strength, toughness, corrosion resistance and thermal stability; S2, according to the chemical composition range determined in step S1, the raw materials are melted and cast to obtain Al-Cu-Mg-Si alloy ingots; S3, the Al-Cu-Mg-Si alloy ingots are subjected to homogenization treatment; S4, the Al-Cu-Mg-Si alloy ingots after homogenization treatment are sawn into aluminum rods and subjected to hot extrusion to obtain extruded profiles; S5, the extruded profiles are subjected to solid solution treatment at a solid solution temperature, and then quenched to room temperature after the solid solution treatment is completed; S6, the extruded profiles after the solid solution treatment and quenching treatment are subjected to tensile straightening treatment; S7, the extruded profiles after stretching are subjected to aging treatment, and then air-cooled to room temperature to obtain Al-Cu-Mg-Si alloy profiles; The chemical composition and mass percentage of the Al-Cu-Mg-Si alloy are as follows: Si 0.6-0.8%, Fe≤0.3%, Cu 4.4-4.8%, Mn 0.8-1.1%, Mg 0.45-0.6%, Zr 0.15-0.18%, Cr 0.1-0.15%, Ni≤0.1%, Zn≤0.2%, Ti≤0.1%, single impurity content≤0.05%, total impurity content≤0.15%, and Al is the balance; The Cu / Mg ratio is 8.0-10.0 to promote the precipitation of Al2CuMg, reduce the precipitation of Al2Cu and AlCuMgMn, and make the Fe and Ni elements in the alloy combine to form the FeNiAl9 phase with good heat resistance, and make the Cu in the alloy fully form the Al2CuMg phase; The homogenization treatment in step S3 adopts a two-stage homogenization process, the first-stage homogenization is heated to 485±5℃ at a heating rate of 35-50℃ / h and is kept for 10-12h, and the second-stage homogenization is heated to 495±5℃ at a heating rate of 15-25℃ / h and is kept for 5-8h; The solid solution treatment in step S5 adopts a two-stage solid solution process, the first-stage initial solid solution temperature is 495±5℃, and the solid solution time is 4-6h; the second-stage strengthening solid solution temperature is 505±5℃, and the solid solution time is 6-8h; After the solid solution treatment is completed, the quenching delay time is controlled to be ≤150s, and the water temperature before and after quenching does not exceed 25℃; The time interval between the completion of quenching and the completion of stretching in step S6 is ≤6h.

2. The method for preparing a high-strength, high-thermal-stability Al-Cu-Mg-Si alloy according to claim 1, characterized in that, The Al-Cu-Mg-Si alloy obtained in step S7 has a yield strength of ≥475MPa, a tensile strength of ≥540MPa, and an elongation after fracture of ≥12%; and after being exposed at 200℃ for 100h, the tensile strength is ≥210MPa, the yield strength is ≥188MPa, and the exfoliation corrosion rating is EB.

3. The method for preparing a high-strength, high-thermal-stability Al-Cu-Mg-Si alloy according to claim 1, characterized in that, The step S2 controls the melt temperature to be less than or equal to 745 DEG C during smelting, and the melt temperature in the smelting furnace before the melt is transferred from the smelting furnace to the refining furnace is 740±5 DEG C; the melt temperature reaching 700 DEG C is taken as the start time of the melt staying in the smelting furnace, the start time of the converter is taken as the end time of the melt staying in the smelting furnace, and the staying time of the melt in the smelting furnace is controlled to be less than or equal to 8 hours; if the staying time exceeds the specified time, the melt is re-stirred and sampled; In the casting process, the casting water temperature is 18-23℃, the starting casting temperature is 735-745℃, the casting temperature is 685-705℃, the casting speed is 31-35mm / min, the water flow is 34-40m 3 / h; and the casting process controls the holding furnace outlet liquid aluminum temperature ≤750℃, and the flow disc hot end casting temperature is 695±10℃.

4. The method for preparing a high-strength, high-thermal-stability Al-Cu-Mg-Si alloy according to claim 1, characterized in that, In the hot extrusion, the mold insulation temperature is set to 385-415 DEG C, the insulation time is 4-36 h, the inner layer heating temperature of the extrusion cylinder is 405-435 DEG C, the aluminum rod insulation temperature is 370-400 DEG C, the extrusion rod speed is 0.2-0.6 mm / s, the single speed-up amount is 0.05 mm / s, and the speed-up completion time is less than or equal to 3 min.

5. The method for preparing a high-strength, high-thermal-stability Al-Cu-Mg-Si alloy according to claim 1, characterized in that, In the aging process, the aging temperature is 175-195 DEG C, and the aging time is 12 h.

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