Variable-temperature creep age forming method of high-strength heat-resistant aluminum alloy profile

Abstract

The invention provides a variable-temperature creep age forming method of a high-strength heat-resistant aluminum alloy profile. The forming method comprises the following steps: firstly, carrying out solution treatment and quenching treatment; then fixing the mold; then, the aluminum alloy profile and the mold are subjected to variable-temperature creep aging heat treatment together; and the aluminum alloy profile and the mold are taken out, unloaded and air-cooled to the room temperature. Wherein the variable-temperature creep aging heat treatment adopts any one of the following two processes: (1) heating from 100 DEG C to 240 DEG C at a constant speed M1 DEG C / h, wherein M1 is more than or equal to 20 and less than or equal to 70; and (2) cooling to 100 DEG C from 240 DEG C at a constant speed M2 DEG C / h, wherein M2 is greater than or equal to 20 and less than or equal to 70. According to the method, the Al-Cu-Mg-Ag series aluminum alloy material is formed while being subjected to heat treatment, and bending forming integrated manufacturing of the high-strength heat-resistant aluminum alloy material can be achieved. The method is simple in process and convenient to operate, the production period can be greatly shortened, and the manufacturing cost is reduced; the method has great application potential in the field of aerospace vehicle preparation.

Description

Technical Field

[0001] The invention relates to the technical field of profile forming and processing, in particular to a variable temperature creep aging forming method for high-strength heat-resistant aluminum alloy profiles. Background Art

[0002] In recent years, creep aging forming technology has been developed for the forming of large aluminum alloy profiles with complex external structures and integral wall panels; it has the advantages of less residual stress and short production cycle. Usually, creep aging forming is carried out at a constant temperature. For example, the invention patents with publication numbers CN108486508B and CN103422035B have developed a single-stage creep aging forming process suitable for Al-Cu and Al-Cu-Mg aluminum alloy sheets; it first pre-deforms the quenched aluminum alloy, then performs aging treatment at a constant temperature, and loads a certain stress at the same time to improve and enhance the mechanical properties of the alloy. For Al-Zn-Mg-Cu alloys, the invention patent with publication number CN102978544B discloses a multi-stage creep aging forming process. Through multi-stage constant temperature aging, the morphology of the creep aging strengthening phase of the alloy can be effectively regulated, the mechanical properties and creep forming properties of the alloy can be improved, the residual stress of the alloy sheet can be reduced, and the exfoliation corrosion resistance of the alloy can be improved.

[0003] During the heat treatment process of large aluminum alloy profiles, due to the different temperature history of the profile surface and the core, it is difficult for the temperature of each part of the profile to be consistent, and the profile actually undergoes a non-isothermal aging process. In recent years, with the maturity of non-isothermal aging heat treatment technology, non-isothermal (variable temperature) creep aging forming has also been developed one after another. In the variable temperature creep aging forming process, the profile is heated and (or) cooled at a certain temperature change rate within the temperature range. Variable temperature aging treatment can greatly reduce the heat treatment time of the profile, save energy, and improve production efficiency. However, the currently available literature shows that the non-isothermal creep aging forming process is mainly used for Al-Zn-Mg-Cu aluminum alloys; it includes at least two stages of heating and cooling aging, and the process is relatively complicated. The invention patent with publication number CN106862377B proposes a non-isothermal vacuum creep forming method for aluminum alloy plates, which states that vacuum creep forming of 2524 aluminum alloy or 7B04 aluminum alloy can be achieved by controlling the heating rate, target temperature and cooling rate. First, the aluminum alloy profile is placed on the mold surface, and then the temperature of the profile is raised to the target temperature (100-340°C) at a heating rate of 0.5-10°C / min, and the target temperature is kept constant for a period of time, and then the profile is cooled at a cooling rate of 1-10°C / min to obtain the formed aluminum alloy profile. It includes three stages: heating, constant temperature and cooling aging, and the aluminum alloy material is not subjected to solid solution treatment and quenching treatment before creep aging; this process is mainly aimed at the forming of aluminum alloy profiles, and the improvement of mechanical properties is limited, and the process is also complicated.

[0004] Creep aging forming is an integrated forming technology developed to meet the processing needs of high-strength aluminum alloy profiles for large integral wall panels for aerospace vehicles. As an aging-strengthened aluminum alloy material, Al-Cu-Mg-Ag aluminum alloy has excellent heat resistance, mechanical properties and fatigue resistance, and is suitable for use as profile materials such as skins and wall panels of aerospace vehicles. Therefore, it is necessary to develop a new, efficient, variable temperature creep aging forming method suitable for Al-Cu-Mg-Ag aluminum alloy, which has broad application prospects. Summary of the invention

[0005] In order to address the deficiencies in the prior art, the present invention provides a variable temperature creep aging forming method for high-strength and heat-resistant aluminum alloy profiles. Through this forming method, the material has excellent mechanical properties while greatly shortening the preparation time of the profiles, thereby improving the production efficiency of the profiles. The method is suitable for preparing large aluminum alloy profiles with high requirements on the strength and heat resistance of the material and with a certain curvature. The method has potential application in the integrated forming preparation of aerospace vehicle profiles.

[0006] In order to achieve the above object, the specific scheme adopted by the present invention is: A variable temperature creep aging forming method for a high-strength heat-resistant aluminum alloy profile, comprising: Step S1, performing solution treatment and quenching treatment on the aluminum alloy profile; Step S2, fixing the aluminum alloy profile using a mold; Step S3, placing the aluminum alloy profile and the mold together in a heat treatment furnace for variable temperature creep aging heat treatment; Step S4, taking out the aluminum alloy profile and the mold, unloading, and air cooling to room temperature; Among them, in step S3, the variable temperature creep aging heat treatment adopts any one of the following two processes: (i) Starting from 100°C, the temperature is raised to 240°C at a constant rate of M1°C / h, 20≤M1≤70; (ii) Cool down from 240°C to 100°C at a constant rate of M2°C / h, 20≤M2≤70.

[0007] Furthermore, in step S1, the solution treatment and quenching treatment process is: after keeping at 510-530° C. for 1-3 hours, immediately quench in water at room temperature.

[0008] Furthermore, the aluminum alloy profile after water quenching at room temperature must be fixed in a mold within a time not exceeding 1 hour.

[0009] Furthermore, in step S2, the mold is a single-curvature surface mold with a surface curvature radius of 500 to 800 mm.

[0010] Furthermore, the aluminum alloy profile is an Al-Cu-Mg-Ag aluminum alloy, wherein the content of the Ag element is 0.1 to 1.0 wt.%.

[0011] Furthermore, the aluminum alloy profile obtained through the temperature-varying creep aging heat treatment has a tensile strength of 520-560 MPa, a yield strength of 470-520 MPa, and an elongation of 7.0%-10.0%.

[0012] The technical principles of the present invention are as follows:

[0013] As an aging-strengthened aluminum alloy, the excellent room temperature and high temperature mechanical properties of Al-Cu-Mg aluminum alloys are mainly derived from the nano heat-resistant strengthening phase particles precipitated during the aging process. For Al-Cu-Mg aluminum alloys containing trace Ag elements, a large number of dispersed nano-sized disc-shaped Ω and θ′ precipitation phases will precipitate during the aging process; as a heat-resistant aluminum alloy, its aging temperature is relatively high, and a higher aging temperature is more conducive to the rapid precipitation of strengthening phases. In the creep aging forming process of Al-Cu-Mg-Ag aluminum alloy, the aluminum alloy material is firstly subjected to sufficient solid solution treatment and quenching treatment, which increases the content of solutes such as Cu, Mg, and Ag in the aluminum matrix, which can effectively promote the precipitation of strengthening phases in the subsequent variable temperature creep aging process. Then it is fixed in a single curvature shaped surface mold with a certain curvature radius (500-800mm) for variable temperature aging forming. During the bending and fixing process, due to the small curvature of the curved surface, the load applied to the aluminum alloy material is less than its yield strength, and the material undergoes elastic deformation, which can reduce the impact of subsequent creep aging forming and is easy to regulate the rebound of the material. In the subsequent variable temperature aging process, the higher aging temperature (100-240°C) and the temperature change rate (20-70°C / h) can enable the material to undergo rapid hardening and forming, avoiding the adverse effects of low temperature (less than 100°C) aging on the aluminum alloy material, while not causing the Ω and θ′ strengthening phase particles to coarsen rapidly, so that it can effectively shorten the forming time of the material and improve the mechanical properties of the material. The present invention can not only enable the material to have excellent mechanical properties, but also enable rapid integrated forming by precisely regulating the variable temperature creep aging process parameters of the Al-Cu-Mg-Ag aluminum alloy material.

[0014] Compared with the prior art, the present invention has the following technical advantages:

[0015] (1) Compared with the traditional method of processing and forming materials after aging heat treatment, the variable temperature creep aging forming process of the present invention can simultaneously process the forming and shaping of aluminum alloy materials, reduce the residual stress of the materials, shorten the production cycle, and save costs. It has important application and economic value in the preparation process of high-performance aluminum alloy products. (2) Compared with other creep aging forming methods, the variable temperature creep aging forming process of the present invention only needs to control the lifting and lowering rate within the temperature range. The method is simple to operate and convenient to adjust parameters, and is more suitable for industrial large-scale production.

[0016] In summary, the present invention treats Al-Cu-Mg-Ag aluminum alloy material, after solution treatment and quenching treatment, and then fixes it on a single-curvature profile mold for variable temperature creep aging heat treatment, and finally unloads it from the mold and air cools it to room temperature, thereby obtaining a single-curved profile with high mechanical properties. During the variable temperature creep aging heat treatment process, the stress in the material is released, and a large number of nano-sized disk-shaped strengthening phase particles are precipitated in the alloy, and the material is formed and formed simultaneously, which reduces the production process and production cycle, saves costs, and is convenient for industrial-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the change of aging temperature with time during the variable temperature creep aging forming process of the present invention.

[0018] Figure 2 This is a TEM image of the product obtained in Example 1.

[0019] Figure 3 This is the TEM image of the product obtained in Comparative Example 1. DETAILED DESCRIPTION

[0020] The present invention discloses a temperature-variable creep aging forming method for a high-strength heat-resistant aluminum alloy profile. The aluminum alloy is an Al-Cu-Mg-Ag series aluminum alloy, and the content of the Ag element is 0.1-1.0wt.%. The specific steps of the forming process are: Step S1, subjecting the Al-Cu-Mg-Ag aluminum alloy material to a solution heat treatment at 510-530° C. for 1-3 hours, and then immediately quenching in water at room temperature; Step S2, fixing the quenched aluminum alloy material into a single curvature shaped surface mold with a curvature radius of 500 to 800 mm; Step S3, placing the aluminum alloy material and the forming mold together into a heat treatment furnace for variable temperature creep aging heat treatment, the aging temperature range is 100-240°C, and the temperature change rate is 20-70°C / h; wherein the quenched aluminum alloy material is kept at room temperature for less than 1 hour; Step S4, unloading the aluminum alloy material from the mold and air cooling it to room temperature.

[0021] It should be noted that the variable temperature creep aging heat treatment in step S3 adopts any one of the following two processes: (i) starting from 100°C and heating to 240°C at a constant rate of M1°C / h, 20≤M1≤70; (ii) Cool from 240°C to 100°C at a constant rate of M2°C / h, 20≤M2≤70.

[0022] After the above-mentioned temperature-variable creep aging treatment, the aluminum alloy profile has a tensile strength of 520-560 MPa, a yield strength of 470-520 MPa, and an elongation of 7.0%-10.0%.

[0023] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0024] Example 1

[0025] This embodiment uses a 3.5 mm thick hot-rolled Al-4.5Cu-1.5Mg-0.1Ag aluminum alloy sheet. The alloy is an Al-Cu-Mg-Ag aluminum alloy prepared by adding 0.1wt.% of Ag element to 2024 aluminum alloy. The temperature-varying creep aging forming process of the aluminum alloy is as follows: Step S1, subjecting the Al-Cu-Mg-Ag aluminum alloy material to a solution heat treatment at 530° C. for 1 h, and then immediately quenching in water at room temperature; Step S2, the aluminum alloy profile after room temperature water quenching is fixed in a single curvature surface mold with a curvature radius of 800 mm within a time not exceeding 1 hour; Step S3, placing the aluminum alloy material and the forming mold together into a heat treatment furnace for variable temperature creep aging heat treatment, starting from 100°C and increasing the temperature to 240°C at a constant rate of 20°C / h; Step S4, taking out the aluminum alloy profile and the mold, unloading the aluminum alloy material from the mold, and air cooling it to room temperature. Finally, a high-strength and heat-resistant aluminum alloy single-curved profile is obtained.

[0026] Example 2

[0027] This embodiment uses a 3.5 mm thick hot-rolled Al-4.5Cu-1.5Mg-1.0Ag aluminum alloy sheet. The alloy is an Al-Cu-Mg-Ag aluminum alloy prepared by adding 1.0 wt.% of Ag element to 2024 aluminum alloy. The temperature-varying creep aging forming process of the aluminum alloy is as follows: Step S1, keeping the Al-Cu-Mg-Ag aluminum alloy material at 520° C. for 2 hours for solution heat treatment, and then immediately quenching with water at room temperature; Step S2, the aluminum alloy profile after room temperature water quenching is fixed in a single curvature surface mold with a curvature radius of 600 mm within a time not exceeding 1 hour; Step S3, placing the aluminum alloy material and the forming mold together into a heat treatment furnace for variable temperature creep aging heat treatment, heating from 100°C to 240°C at a constant rate of 70°C / h; Step S4, taking out the aluminum alloy profile and the mold, unloading the aluminum alloy material from the mold, and air cooling it to room temperature. Finally, a high-strength and heat-resistant aluminum alloy single-curved profile is obtained.

[0028] Example 3

[0029] This embodiment uses a 3.5 mm thick hot-rolled Al-4.5Cu-1.5Mg-0.5Ag aluminum alloy sheet. The alloy is an Al-Cu-Mg-Ag aluminum alloy prepared by adding 0.5wt.% of Ag element to 2024 aluminum alloy. The temperature-varying creep aging forming process of the aluminum alloy is as follows: Step S1, keeping the Al-Cu-Mg-Ag aluminum alloy material at 530° C. for 1 hour for solution heat treatment, and then immediately quenching with water at room temperature; Step S2, the aluminum alloy profile after room temperature water quenching is fixed in a single curvature surface mold with a curvature radius of 700 mm within a time not exceeding 1 hour; Step S3, placing the aluminum alloy material and the forming mold together into a heat treatment furnace for variable temperature creep aging heat treatment, cooling from 240°C to 100°C at a constant rate of 20°C / h; Step S4, taking out the aluminum alloy profile and the mold, unloading the aluminum alloy material from the mold, and air cooling it to room temperature. Finally, a high-strength and heat-resistant aluminum alloy single-curved profile is obtained.

[0030] Example 4

[0031] This embodiment uses a 3.5 mm thick hot-rolled Al-4.5Cu-1.5Mg-0.8Ag aluminum alloy sheet. The alloy is an Al-Cu-Mg-Ag aluminum alloy prepared by adding 0.8 wt.% of Ag element to 2024 aluminum alloy. The temperature-variable creep aging forming process of the aluminum alloy is as follows: Step S1, subjecting the Al-Cu-Mg-Ag aluminum alloy material to a solution heat treatment at 520° C. for 3 h, and then immediately water quenching at room temperature; Step S2, the aluminum alloy profile after room temperature water quenching is fixed in a single curvature surface mold with a curvature radius of 500 mm within a time not exceeding 1 hour; Step S3, placing the aluminum alloy material and the forming mold together into a heat treatment furnace for variable temperature creep aging heat treatment, cooling from 240°C to 100°C at a constant rate of 70°C / h; Step S4, taking out the aluminum alloy profile and the mold, unloading the aluminum alloy material from the mold, and air cooling it to room temperature. Finally, a high-strength and heat-resistant aluminum alloy single-curved profile is obtained.

[0032] Comparative Example 1

[0033] This embodiment uses a 3.5 mm thick hot-rolled Al-4.5Cu-1.5Mg-0.5Ag aluminum alloy sheet. The alloy is an Al-Cu-Mg-Ag aluminum alloy prepared by adding 0.5wt.% of Ag element to 2024 aluminum alloy. The aging forming process of the aluminum alloy is as follows: Step S1, subjecting the Al-Cu-Mg series aluminum alloy material to a solution heat treatment at 520° C. for 2 hours, and then immediately water quenching at room temperature; Step S2, subjecting the aluminum alloy material to a 3% pre-stretching deformation treatment; Step S3, placing the aluminum alloy material into a heat treatment furnace and performing isothermal aging heat treatment at 160° C. for 16 hours; finally, obtaining a T8 aluminum alloy material.

[0034] Effect analysis

[0035] 1) Microstructure analysis

[0036] The microstructure of Al-Cu-Mg-Ag aluminum alloy after temperature-varying creep aging forming treatment and isothermal aging heat treatment was observed and analyzed; Figure 2 is a TEM image of the Al-Cu-Mg-Ag alloy after temperature-variable creep aging treatment in Example 1, Figure 3 This is a TEM image of the Al-Cu-Mg-Ag alloy after isothermal aging treatment in Comparative Example 1. Figure 2 and Figure 3 It can be seen that after the present invention performs temperature-variable creep aging forming treatment on the Al-Cu-Mg aluminum alloy containing Ag, denser and finer Ω and θ′ strengthening phase particles are precipitated in the alloy, which makes the alloy show higher mechanical properties.

[0037] 2) Analysis of mechanical properties and aging forming time

[0038] The Vickers hardness and room temperature tensile properties of the Al-Cu-Mg-Ag aluminum alloy materials prepared in Examples 1-4 and Comparative Example 1 were tested, and the aging forming time was recorded, and the results are shown in Table 1. Among them, the room temperature tensile test in each embodiment adopts GB / T 228.1-2010, and the tensile direction of the sample is along the rolling direction of the plate; the Vickers hardness test adopts GB / T4340.4-2009.

[0039] Table 1 Performance test results of aluminum alloy profiles obtained in Examples 1-4 and Comparative Example 1

[0040] As can be seen from Table 1, compared with Comparative Example 1, Examples 1-4 use Figure 1The Al-Cu-Mg-Ag aluminum alloy profiles prepared by the variable temperature creep aging forming method shown in each embodiment maintain the excellent mechanical properties of the material on the basis of greatly reducing the total creep aging forming time.

[0041] In summary, the present invention improves the mechanical properties of the alloy by performing variable temperature creep aging forming treatment on the Al-Cu-Mg-Ag aluminum alloy and regulating the variable temperature creep aging forming process parameters of the alloy. At the same time, the creep forming time of the profile is greatly reduced, the production efficiency of the profile is improved, and the production cost of the profile is reduced, thereby realizing the integrated forming and forming of high-strength and heat-resistant aluminum alloy profiles.

[0042] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Any equivalent changes or modifications made according to the essence of the present invention should be included in the protection scope of the present invention.

Claims

1. A temperature-variable creep aging forming method for high-strength heat-resistant aluminum alloy profiles, characterized in that: include: Step S1, performing solution treatment and quenching treatment on the aluminum alloy profile; Step S2, fixing the aluminum alloy profile using a mold; Step S3, placing the aluminum alloy profile and the mold together in a heat treatment furnace for variable temperature creep aging heat treatment; Step S4, taking out the aluminum alloy profile and the mold, unloading, and air cooling to room temperature; Among them, in step S3, the variable temperature creep aging heat treatment adopts any one of the following two processes: (i) Starting from 100 °C, the temperature is raised to 240 °C at a constant rate of M1 °C / h, 20≤M1≤70; (ii) Start cooling from 240 ℃ to 100 ℃ at a constant rate of M2 ℃ / h, 20≤M2≤70.

2. The temperature-variable creep aging forming method for a high-strength heat-resistant aluminum alloy profile according to claim 1, characterized in that: In step S1, the solution treatment and quenching treatment process is: keep at 510-530 °C for 1-3 h, and then immediately quench in water at room temperature.

3. The temperature-variable creep aging forming method for a high-strength heat-resistant aluminum alloy profile according to claim 2, characterized in that: After room temperature water quenching, the aluminum alloy profile must be fixed in the mold within no more than 1 hour.

4. The temperature-variable creep aging forming method for a high-strength heat-resistant aluminum alloy profile according to claim 1, characterized in that: In step S2, the mold is a single-curvature surface mold with a surface curvature radius of 500-800 mm.

5. The temperature-variable creep aging forming method for a high-strength heat-resistant aluminum alloy profile according to claim 1, characterized in that: The aluminum alloy profile is an Al-Cu-Mg-Ag aluminum alloy, wherein the content of the Ag element is 0.1-1.0 wt.%.

6. The temperature-variable creep aging forming method for high-strength heat-resistant aluminum alloy profiles according to claim 1, characterized in that: The tensile strength of the aluminum alloy profile obtained after temperature-varying creep aging heat treatment is 520~560 MPa, the yield strength is 470~520 MPa, and the elongation is 7.0%~10.0%.

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