A method of aging a 7xxx-series aluminum alloy based on precursor-induced precipitation

Abstract

The present application relates to non-ferrous metal processing technical field, specifically provide a kind of 7xxx series aluminum alloy aging method based on precursor induced precipitation.The 7xxx series aluminum alloy aging method based on precursor induced precipitation provided by the present application includes the following steps: S1.workpiece is sequentially subjected to solution treatment and quenching treatment;S2.workpiece after step S1 processing is subjected to three-stage aging treatment, and product is obtained;The three-stage aging treatment includes: first at first-stage aging temperature T1 1-6h is kept, then with 2-8 ℃ / h rate is heated to second-stage aging temperature T2, keeps 2-6h after, again at third-stage aging temperature T3 3-18h is kept;Wherein, T1 is 60-100 ℃, T2 is 110-140 ℃, T3 is 120-180 ℃, and T3>T2.The present application uses sectional type solution treatment combined with three-stage aging treatment, forms the microstructure of "intra-crystalline uniform dispersion η', η strengthening phase, grain boundary larger and intermittent distribution η phase" in aluminum alloy, can effectively improve the tensile property and fracture toughness of 7xxx series aluminum alloy.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal processing technology, and in particular to an aging method for 7xxx series aluminum alloys based on precursor-induced precipitation. Background Technology

[0002] With the increasing demand for high-strength and lightweight materials in the aerospace industry, 7xxx series aluminum alloys have been widely used due to their excellent mechanical properties. Precursor-induced precipitation aging technology is one of the main methods to optimize the microstructure and mechanical properties of 7xxx series aluminum alloys. The principle of this technology is to introduce specific precursors into the alloy, which then act as nucleation sites for precipitates during the subsequent aging process. This allows for precise control of the quantity, size, and distribution of precipitates, thereby improving the material's strength, toughness, and fatigue resistance.

[0003] However, existing precursor-induced aging technologies for 7xxx series aluminum alloys still suffer from the following problems in practical applications, severely restricting their industrial application: On the one hand, the formation of precursors in traditional processes relies on a pre-precipitation treatment step, which requires long-term holding at low temperatures. This not only prolongs the overall process cycle and increases time costs but also increases process complexity due to the additional processing step. Simultaneously, low-temperature, long-term aging requires equipment with precise temperature control capabilities over a wide temperature range, significantly increasing equipment investment costs. Furthermore, temperature control deviations can easily lead to over-aging, causing fluctuations in product performance. On the other hand, some technologies use the addition of alloying elements such as Sc and Zr to form nanoscale compounds as precipitate nuclei, but their size, morphology, and distribution density are difficult to control precisely, easily leading to uneven precipitate distribution, localized coarsening, or insufficient quantity, resulting in unstable material mechanical properties and difficulty in simultaneously improving strength and toughness. Therefore, there is an urgent need to develop an aging technology that simplifies the process, shortens the cycle, reduces equipment dependence, and simultaneously achieves precise precursor control. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides an aging method for 7xxx series aluminum alloys based on precursor-induced precipitation. The method employs a segmented solution treatment combined with a three-stage aging treatment to form a microstructure within the aluminum alloy consisting of "uniformly dispersed η' and η strengthening phases within the grains, and η phases with large and discontinuous grain boundaries." This method can effectively improve the tensile properties and fracture toughness of 7xxx series aluminum alloys.

[0005] To address the aforementioned technical problems, in a first aspect, the present invention provides an aging method for 7xxx series aluminum alloys based on precursor-induced precipitation, comprising the following steps: S1. Perform solution treatment and quenching treatment on the workpiece in sequence; S2. Perform a three-stage aging treatment on the workpiece processed in step S1 to obtain the finished product; The three-stage aging treatment includes: first, holding at the first-stage aging temperature T1 for 1-6 hours, then raising the temperature to the second-stage aging temperature T2 at a rate of 2-8℃ / h, holding for 2-6 hours, and then holding at the third-stage aging temperature T3 for 3-18 hours; wherein T1 is 60-100℃, T2 is 110-140℃, T3 is 120-180℃, and T3 > T2.

[0006] This invention achieves uniform precipitation of the strengthening phase induced by intragranular precursors and orderly evolution of the η-phase at grain boundaries through a progressive three-stage aging process from low to medium to high temperature, thereby synergistically improving the strength and toughness of the material. The first-stage aging treatment (T1 at 60-100℃) promotes the aggregation of solute atoms in the supersaturated solid solution through short-range diffusion, forming uniformly distributed GP regions and early η' precursors, providing sufficient and dispersed nucleation nuclei for subsequent strengthening phase precipitation. Subsequently, the temperature is slowly increased from the first-stage aging treatment T1 to the second-stage aging temperature T2 (110-140℃) at a rate of 2-8℃ / h. This process guides the three-phase coexistence state of the intragranular GP regions, η' phase, and α-Al matrix towards a three-phase coexistence state of η', η, and α-Al. The process involves ordered evolution of the η' strengthening phase. By controlling the directional migration rate of solute atoms, the η' strengthening phase undergoes uniform nucleation around the precursor, ultimately forming a fine and diffusely distributed strengthening phase. The third-stage aging treatment (T3 at 120-180℃, where T3 > T2) further promotes the stable growth of the η' phase within the grains and maintains its fine size to sustain high strength. Simultaneously, the low-melting-point phases (such as the η phase) in the grain boundary regions transform from continuously distributed flakes to discontinuously distributed spherical or short rod-shaped structures, reducing grain boundary brittleness and alleviating stress concentration, effectively improving fracture toughness. This invention solves the problems of uneven precipitate distribution and difficulty in balancing strength and toughness in traditional processes through an aging mechanism of "rapid nucleation-slow control-gradient optimization," significantly improving the overall mechanical properties of the alloy. Furthermore, it eliminates the need for additional pre-precipitation treatment steps, shortening the process cycle.

[0007] Preferably, the workpiece is a modified 7xxx series aluminum alloy, such as rolled sheet, extruded bar, forging or tube.

[0008] Preferably, the 7xxx series aluminum alloy is selected from 7075 aluminum alloy, 7050 aluminum alloy, 7055 aluminum alloy, 7065 aluminum alloy, 7150 aluminum alloy, 7005 aluminum alloy, 7010 aluminum alloy, 7175 aluminum alloy, 7475 aluminum alloy, etc.

[0009] Preferably, in step S1, the solution treatment is a two-stage solution treatment. The temperature of the first-stage solution treatment is 410-460℃, and the treatment time is 1-6h. The temperature of the second-stage solution treatment is 430-490℃, and the treatment time is 1-10h. More preferably, the temperature of the second-stage solution treatment is higher than the temperature of the first-stage solution treatment.

[0010] The optimized two-stage solution treatment, through stepped heating and segmented holding, improves both the solution effect and microstructure stability: the first stage of solution treatment initially dissolves the low-melting-point phase, while the low-temperature holding slows down grain growth; the second stage of solution treatment uses a higher temperature to specifically promote the full dissolution of the insoluble phase into the matrix, further eliminating component segregation and releasing internal stress. This segmented solution treatment avoids the problems of overheating and abnormal grain coarsening that can easily occur with single high-temperature solution treatment, and achieves full dissolution of solute elements through a stepped dissolution mechanism, laying a uniform and stable microstructure foundation for the uniform nucleation and orderly precipitation of strengthening phases during subsequent aging.

[0011] Preferably, in step S1, the quenching solution is selected from water, aqueous solutions, or water-soluble quenching media. Aqueous solutions are selected from, for example, aqueous solutions of polyvinyl alcohol, aqueous solutions of polyethylene glycol, aqueous solutions of polyether, aqueous solutions of polyacrylamide, etc.; water-soluble quenching media are selected from, for example, water-soluble quenching oil, etc.

[0012] Preferably, in step S1, the temperature of the quenching solution is 10-60℃ during the quenching process.

[0013] Preferably, in step S1, during the quenching process, the required volume of the quenching solution is calculated based on the workpiece mass to ensure that the temperature rise of the quenching solution is controlled within 5°C.

[0014] Preferably, in step S2, after the three-stage aging treatment is completed, the material is cooled by furnace cooling, air cooling, or air cooling.

[0015] Secondly, the present invention also provides a 7xxx series aluminum alloy, which is prepared by the above-mentioned aging method of 7xxx series aluminum alloy based on precursor-induced precipitation.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention proposes an aging technology for 7xxx series aluminum alloys based on precursor-induced uniform precipitation. It employs a segmented solution treatment combined with a three-stage aging process to form a microstructure within the aluminum alloy consisting of uniformly dispersed intragranular η' and η-strengthening phases, and η phases with relatively large and discontinuous grain boundaries. This effectively improves the tensile properties and fracture toughness of 7xxx series aluminum alloys, achieving a synergistic enhancement of strength and toughness. Compared with traditional processes, this invention eliminates the need for a low-temperature pre-precipitation treatment step by precisely controlling the temperature (e.g., stepped solution temperature, gradient aging temperature) and time parameters at each stage, saving time in low-temperature aging. Simultaneously, it simplifies the process flow, reduces the stringent temperature control requirements on equipment, and is more conducive to industrial application. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the aging temperature curve of the three-stage aging process in Embodiment 1 of the present invention. Detailed Implementation

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the specific embodiments will be briefly introduced below. Obviously, the embodiments described below are some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these embodiments without creative effort.

[0019] Where specific experimental steps or conditions are not specified in the embodiments, they can be performed according to the conventional experimental steps or conditions described in the literature in this field. All raw materials or instruments used are commercially available conventional products, including but not limited to those used in the embodiments of this application.

[0020] Example 1 This embodiment provides an aging method for 7075 aluminum alloy based on precursor-induced precipitation, including the following steps: (1) The 7075 aluminum alloy rolled plate with a thickness of 5mm was subjected to two-stage solution treatment. First, it was kept at 430℃ for 3h and then at 460℃ for 5h. Then, the solution-treated rolled plate was placed in water at 25℃ for quenching treatment, and the temperature rise of the quenching solution was controlled within 5℃ (the actual temperature after quenching was 26℃). (2) The quenched rolled plate is subjected to a three-stage aging treatment. First, it is held at 80℃ for 4 hours, then the temperature is increased to 120℃ at a rate of 4℃ / h, held for 4 hours, and then held at 140℃ for 8 hours. The aging temperature curve during the entire three-stage aging treatment is shown in the figure. Figure 1 As shown; after aging, air cooling is used to obtain the finished 7075 aluminum alloy rolled plate.

[0021] Example 2 This embodiment provides an aging method for 7050 aluminum alloy based on precursor-induced precipitation, including the following steps: (1) The 7050 aluminum alloy extrusion bar with a diameter of 20mm was subjected to two-stage solution treatment. First, it was kept at 440℃ for 2h, and then kept at 470℃ for 6h. Then, the solution-treated plate was placed in water at 40℃ for quenching treatment, and the temperature rise of the quenching solution was controlled within 5℃ (the actual temperature after quenching was 42℃). (2) The quenched rolled plate is subjected to three-stage aging treatment. First, it is held at 90℃ for 3 hours, then heated to 130℃ at a rate of 6℃ / h, held for 5 hours, and then held at 160℃ for 12 hours. After aging, it is cooled by air cooling to obtain the finished 7050 aluminum alloy extrusion bar.

[0022] Example 3 This embodiment provides an aging method for 7055 aluminum alloy based on precursor-induced precipitation, including the following steps: (1) A 100kg 7055 aluminum alloy forging was subjected to two-stage solution treatment. First, it was kept at 420℃ for 4h, and then at 480℃ for 8h. Then, the solution-treated rolled plate was placed in water at 50℃ for quenching treatment, and the temperature rise of the quenching solution was controlled within 5℃ (the actual temperature after quenching was 54℃). (2) The quenched rolled plate is subjected to three-stage aging treatment. First, it is held at 70℃ for 5 hours, then heated to 110℃ at a rate of 3℃ / h, held for 4 hours, and then held at 155℃ for 10 hours. After aging, it is cooled by air cooling to obtain the finished 7055 aluminum alloy forging.

[0023] Example 4 This embodiment provides an aging method for 7065 aluminum alloy based on precursor-induced precipitation, including the following steps: (1) A 7065 aluminum alloy thick-walled tube with an outer diameter of 100 mm and a wall thickness of 10 mm was subjected to two-stage solution treatment. First, it was kept at 450℃ for 1.5 h, and then kept at 490℃ for 7 h. Then, the solution-treated rolled plate was placed in water at 10℃ for quenching treatment, and the temperature rise of the quenching solution was controlled within 5℃ (the actual temperature after quenching was 12℃). (2) The quenched rolled plate is subjected to three-stage aging treatment. First, it is held at 65℃ for 6 hours, then the temperature is increased to 115℃ at a rate of 2℃ / h, held for 6 hours, and then held at 180℃ for 15 hours. After aging, it is cooled by air cooling to obtain the finished 7065 aluminum alloy thick-walled tube.

[0024] Comparative Example 1 This comparative example provides an aging method for 7075 aluminum alloy, including the following steps: (1) A 7075 aluminum alloy rolled plate with a thickness of 5 mm was subjected to solution treatment and kept at 460℃ for 8 hours; then the plate after solution treatment was placed in water at a temperature of 25℃ for quenching treatment, and the temperature rise of the quenching solution was controlled within 5℃ (the actual temperature after quenching was 26℃). (2) The quenched rolled plate is subjected to aging treatment and held at 140℃ for 10h; after aging, it is cooled by air cooling to obtain the finished 7075 aluminum alloy rolled plate.

[0025] Comparative Example 2 This comparative example provides an aging method for 7075 aluminum alloy, including the following steps: (1) The 7075 aluminum alloy rolled plate with a thickness of 5mm was subjected to two-stage solution treatment. First, it was kept at 430℃ for 3h and then at 460℃ for 5h. Then, the solution-treated rolled plate was placed in water at 25℃ for quenching treatment, and the temperature rise of the quenching solution was controlled within 5℃ (the actual temperature after quenching was 26℃). (2) The quenched rolled plate is subjected to a two-stage aging treatment. First, it is held at 120℃ for 8 hours, and then the temperature is increased to 140℃ at a rate of 200℃ / h and held for 8 hours. After aging, it is cooled by air cooling to obtain the finished 7075 aluminum alloy rolled plate.

[0026] Comparative Example 3 This comparative example provides an aging method for 7075 aluminum alloy, including the following steps: (1) The 7075 aluminum alloy rolled plate with a thickness of 5mm was subjected to two-stage solution treatment. First, it was kept at 430℃ for 3h and then at 460℃ for 5h. Then, the solution-treated rolled plate was placed in water at 25℃ for quenching treatment, and the temperature rise of the quenching solution was controlled within 5℃ (the actual temperature after quenching was 26℃). (2) The quenched rolled plate is subjected to three-stage aging treatment. First, it is held at 80℃ for 4 hours, then the temperature is increased to 120℃ at a rate of 200℃ / h, held for 4 hours, and then held at 140℃ for 8 hours. After aging, it is cooled by air cooling to obtain the finished 7075 aluminum alloy rolled plate.

[0027] Performance testing The performance of the 7xxx series aluminum alloy products prepared in Examples 1-4 and Comparative Examples 1-3 was tested. The test standards for tensile strength, yield strength, elongation and fracture toughness were in accordance with GB / T 16865-2013. The equipment was EMSYS electronic universal testing machine. The test environment was 23.7℃ and 45.0%RH. The results are shown in Table 1 below.

[0028] Table 1 As can be seen from Table 1, the present invention, through the "two-stage solution treatment + three-stage aging" process, improves the tensile strength and yield strength of 7xxx series aluminum alloys while maintaining good elongation and fracture toughness, effectively solving the problem of difficulty in balancing strength and toughness in traditional processes.

[0029] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An aging method for 7xxx series aluminum alloys based on precursor-induced precipitation, characterized in that, Includes the following steps: S1. Perform solution treatment and quenching treatment on the workpiece in sequence; S2. Perform a three-stage aging treatment on the workpiece processed in step S1 to obtain the finished product; The three-stage aging treatment includes: first, holding at the first-stage aging temperature T1 for 1-6 hours, then raising the temperature to the second-stage aging temperature T2 at a rate of 2-8℃ / h, holding for 2-6 hours, and then holding at the third-stage aging temperature T3 for 3-18 hours; wherein T1 is 60-100℃, T2 is 110-140℃, T3 is 120-180℃, and T3 > T2.

2. The aging method for 7xxx series aluminum alloys based on precursor-induced precipitation as described in claim 1, characterized in that, The workpiece is a modified 7xxx series aluminum alloy.

3. The aging method for 7xxx series aluminum alloys based on precursor-induced precipitation as described in claim 1, characterized in that, In step S1, the solution treatment is a two-stage solution treatment.

4. The aging method for 7xxx series aluminum alloys based on precursor-induced precipitation as described in claim 3, characterized in that, In the solution treatment, the temperature of the first stage solution treatment is 410-460℃ and the treatment time is 1-6h; the temperature of the second stage solution treatment is 430-490℃ and the treatment time is 1-10h.

5. The aging method for 7xxx series aluminum alloys based on precursor-induced precipitation as described in claim 3 or 4, characterized in that, In the solution treatment, the temperature of the second-stage solution treatment is higher than the temperature of the first-stage solution treatment.

6. The aging method for 7xxx series aluminum alloys based on precursor-induced precipitation as described in claim 1, characterized in that, In step S1, the quenching solution in the quenching process is selected from water, aqueous solutions, or water-soluble quenching media.

7. The aging method for 7xxx series aluminum alloys based on precursor-induced precipitation as described in claim 1, characterized in that, In step S1, the temperature of the quenching solution during the quenching process is 10-60℃.

8. The aging method for 7xxx series aluminum alloys based on precursor-induced precipitation as described in claim 1, characterized in that, In step S1, during the quenching process, the temperature rise of the quenching solution is controlled within 5°C.

9. The aging method for 7xxx series aluminum alloys based on precursor-induced precipitation as described in claim 1, characterized in that, In step S2, after the three-stage aging process is completed, the material is cooled by furnace cooling, air cooling, or air cooling.

10. A 7xxx series aluminum alloy, characterized in that, It is prepared by the aging method of 7xxx series aluminum alloy based on precursor-induced precipitation as described in any one of claims 1-9.

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