Preparation method of 7075 alloy with high strength, plasticity and conductivity

Abstract

The invention relates to the technical field of aluminum alloy preparation and processing, and discloses a high-strength plasticity high-conductivity 7075 alloy preparation method which comprises the following steps: S1, two-stage soaking annealing: heating a cast ingot to a first-stage annealing temperature and preserving heat to complete first-stage soaking annealing; then the cast ingot is continuously heated to the second-stage annealing temperature, heat preservation is conducted again, second-stage soaking annealing is completed, and the cast ingot is cooled to the room temperature; the cast ingot cooled to the room temperature is heated to the hot rolling temperature for hot rolling, a plate is obtained after the cast ingot is subjected to hot rolling deformation, and the plate is cooled to the room temperature; s3, cold rolling deformation is conducted, specifically, the cooled plate is subjected to cold rolling, and the plate is subjected to cold rolling deformation; s4, carrying out two-stage solid solution treatment; s5, water quenching at room temperature; and S6, two-stage aging treatment or three-stage aging treatment. According to the 7075 aluminum alloy sheet prepared through the method, the tensile strength reaches 600 MPa, the yield strength reaches 590 MPa, the elongation reaches 12%, and the conductivity reaches 33.8% IACS. The method can utilize the existing process equipment and is suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy preparation and processing, and in particular to a method for preparing a high-strength, plasticity and high-conductivity 7075 alloy. Background Art

[0002] 7075 aluminum alloy has the characteristics of good mechanical properties, good wear resistance, corrosion resistance, high specific strength, etc. Its thin plates, forgings, profiles, etc. are mainly used as materials for important structures such as aerospace, mechanical equipment, mold processing, transportation, etc. With the continuous development of industries such as aerospace, transportation, etc., the application scope of 7075 deformed aluminum alloy is constantly expanding, and the requirements for the fracture toughness and corrosion resistance of the alloy are further improved. Studies have shown that the fracture toughness and corrosion resistance of deformed 7075 aluminum alloy are related to the impurity content of Fe and Si. The lower the impurity content, the better the strength, plasticity and corrosion resistance of the alloy. The impurity content is related to the quality of the ingot, and it is required to optimize the melting and casting process to prepare aluminum alloy ingots with lower impurity content. At the same time, the deformation heat treatment process also has a great influence on the performance of 7075 aluminum alloy. At present, the yield strength of 7075 aluminum alloy thin plate (1-3mm) is low (less than 500MPa), and the electrical conductivity is lower than 30%IACS. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for preparing a high-strength, ductile and high-conductivity 7075 alloy by regulating the deformation and heat treatment processes and optimizing the process conditions to obtain a thin plate material with high strength, ductility and high conductivity, and the plate has good rolling performance.

[0004] In order to achieve the above-mentioned purpose of the invention, the technical solution adopted by the present invention is: a method for preparing a high-strength, ductile and high-conductivity 7075 alloy, comprising the following steps:

[0005] S1, double-stage soaking annealing: the ingot is heated to the first-stage annealing temperature and kept warm to complete the first-stage soaking annealing; then the ingot is further heated to the second-stage annealing temperature and kept warm again to complete the second-stage soaking annealing, and the ingot is cooled to room temperature;

[0006] S2, hot rolling deformation: the ingot cooled to room temperature is heated to the hot rolling temperature for hot rolling, the ingot is subjected to hot rolling deformation to obtain a plate, and the plate is cooled to room temperature;

[0007] S3, cold rolling deformation: the cooled sheet is cold rolled, and the sheet undergoes cold rolling deformation;

[0008] S4, double-stage solution treatment: the cold-rolled plate is heated to the first-stage solution temperature and kept warm; the plate is further heated to the second-stage solution temperature and kept warm again to complete the double-stage solution treatment;

[0009] S5, room temperature water quenching: the plate after the double-stage solid solution treatment is water quenched at room temperature;

[0010] S6, double-stage aging or triple-stage aging treatment: The water-quenched plate is subjected to double-stage aging treatment or triple-stage aging treatment to obtain a high-strength, ductile and high-conductivity 7075 alloy.

[0011] Furthermore, in the above-mentioned method for preparing high-strength, ductility and high-conductivity 7075 alloy, the first-stage annealing temperature in S1 is 380°C to 450°C, and the holding time at the first-stage annealing temperature is 300min to 1800min; the second-stage annealing temperature is 460°C to 480°C, and the holding time at the second-stage annealing temperature is 900min to 2400min.

[0012] Furthermore, in the above-mentioned method for preparing the high-strength, ductility and high-conductivity 7075 alloy, the hot rolling temperature in S2 is 400° C. to 430° C., and the hot rolling deformation is 60% to 90%.

[0013] Furthermore, in the above-mentioned method for preparing the high-strength, ductility and high-conductivity 7075 alloy, the cold rolling deformation amount in S3 is 60% to 90%.

[0014] Furthermore, in the above-mentioned method for preparing the high-strength, ductility and high-conductivity 7075 alloy, in S4, the first-stage solid solution temperature is 430°C to 450°C, and the holding time at the first-stage solid solution temperature is 10min to 60min; the second-stage solid solution temperature is 470°C to 480°C, and the holding time at the second-stage solid solution temperature is 60min to 180min.

[0015] Furthermore, in the above-mentioned method for preparing the high-strength, ductile and high-conductivity 7075 alloy, the temperature of water during water quenching in S5 is ≤25°C, and the transition time from the end of the two-stage solid solution to the water quenching does not exceed 10 minutes.

[0016] Furthermore, in the above-mentioned method for preparing the high-strength, ductility and high-conductivity 7075 alloy, the double-stage aging treatment in S6 is specifically as follows: heating the water-quenched plate to 100°C to 125°C and keeping it warm for 300min to 600min; then heating the plate to 130°C to 170°C and continuing to keep it warm for 300min to 1800min to complete the double-stage aging treatment, and cooling the plate to room temperature to obtain the high-strength, ductility and high-conductivity 7075 alloy.

[0017] Furthermore, in the above-mentioned method for preparing the high-strength, ductility and high-conductivity 7075 alloy, the three-level aging treatment in S6 is specifically as follows: heating the water-quenched plate to 100°C to 125°C and keeping it warm for 300min to 600min; then heating the plate to 130°C to 170°C and continuing to keep it warm for 300min to 1800min; finally, restoring the heating temperature of the plate to 100°C to 125°C and keeping it warm for 1200min to 1800min, completing the three-level aging treatment, and cooling the plate to room temperature to obtain the high-strength, ductility and high-conductivity 7075 alloy.

[0018] The beneficial effects of the present invention are as follows: the present invention adopts a combination of double-stage soaking annealing, hot rolling deformation, cold rolling deformation, double-stage solution treatment, room temperature water quenching, double-stage or three-stage aging treatment, etc. Through double-stage soaking annealing, the heating rate, holding temperature, holding time and other process parameters in the soaking annealing process are controlled, so that the dendrite segregation and grain boundary non-equilibrium solidification phase in the ingot are greatly reduced, which is a high-quality ingot for subsequent rolling. The purpose of the first-stage soaking annealing is to eliminate the low-melting point non-equilibrium phase such as T (AlZnMgCu) phase in the ingot and reduce dendrite segregation. The purpose of the second-stage soaking annealing is to further reduce the number of high-melting point non-equilibrium phases such as MgZn2, Al2Cu, Al2CuMg on the grain boundary in the ingot, and accelerate the diffusion of solute elements such as Zn, Mg, Cu in the dendrite, and then control the cooling rate to prevent the dispersion and precipitation of η (MgZn2) phase in the ingot, and finally obtain a high-homogeneity ingot.

[0019] By controlling the hot rolling temperature and deformation, the annealed ingot grains are broken and a fine-grained fiber rolling structure is obtained. Cold rolling deformation provides energy storage for the plate and energy for subsequent recovery recrystallization. The purpose of the double-stage solution treatment is to further dissolve the residual crystalline phase T (AlZnMgCu) phase during the cold rolling deformation process, and the elements such as Zn, Mg, and Cu are fully dissolved into the aluminum matrix, while forming a certain volume fraction of fine recrystallization. The purpose of room temperature water quenching is to obtain the maximum supersaturation of the plate after solution treatment, and provide sufficient energy and nucleation particles for subsequent aging treatment. The purpose of double-stage or triple-stage aging treatment is to make the quenched plate discontinuously precipitate η (MgZn2) phase at the grain boundary during the aging process, reduce the potential difference between the grain boundary and the interior, and increase the grain boundary strength, thereby improving the conductivity and plasticity of the plate, and precipitate the dispersed nano-precipitation phase η' (MgZn2) phase in the crystal to improve the strength of the alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a flow chart of the preparation method. DETAILED DESCRIPTION

[0021] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0022] Examples 1 to 6 all use large-size 7075 aluminum alloy flat ingots as ingots, and the ingots are sequentially subjected to two-stage soaking annealing, hot rolling deformation, cold rolling deformation, two-stage solid solution treatment, room temperature water quenching, and two-stage or three-stage aging treatment. Figure 1 shown.

[0023] Example 1

[0024] Double-stage soaking annealing treatment: first heat the ingot to 380°C and keep it warm for 1800 min; then continue to heat the ingot to 460°C and keep it warm for 2400 min; cool the ingot after the second-stage soaking annealing treatment to room temperature.

[0025] Hot rolling and cold rolling treatment: The ingot that has undergone double-stage soaking annealing is hot rolled at 400°C into a 1mm plate with a total deformation of 60%, then cooled to room temperature and the plate is further cold rolled with a total deformation of 70%.

[0026] Two-stage solution treatment: Heat the cold-rolled plate to 430°C, keep it warm for 60 minutes, then continue to heat it to 470°C and keep it warm for 180 minutes.

[0027] Water quenching: The plate after solution treatment is water quenched to 25°C, and the transfer time from solution treatment to water quenching is 5 minutes.

[0028] Double-stage aging treatment: heat the water-quenched plate to 100°C, keep it warm for 600 minutes, then heat it to 130°C, keep it warm for 1800 minutes, and cool it to room temperature.

[0029] Example 2

[0030] Double-stage soaking annealing treatment: first heat the ingot to 380°C and keep it warm for 1800 min; then continue to heat the ingot to 460°C and keep it warm for 2400 min; cool the ingot after the second-stage soaking annealing treatment to room temperature.

[0031] Hot rolling and cold rolling treatment: The ingot that has undergone double-stage soaking annealing is hot rolled at 400°C into a 1mm plate with a total deformation of 60%, then cooled to room temperature and the plate is further cold rolled with a total deformation of 70%.

[0032] Double-stage solution treatment: Heat the cold-rolled plate to 450°C, keep it warm for 20 minutes, then continue to heat it to 480°C and keep it warm for 60 minutes.

[0033] Water quenching: The plate after solution treatment is water quenched to 20°C, and the transfer time from solution treatment to water quenching is 10 minutes.

[0034] Double-stage aging treatment: heat the water-quenched plate to 125℃ for 300min, then heat to 170℃ for 300min, and cool to room temperature.

[0035] Example 3

[0036] Double-stage soaking annealing treatment: first heat the ingot to 450°C and keep it warm for 300 minutes; then continue to heat the ingot to 480°C and keep it warm for 900 minutes; cool the ingot after the second-stage soaking annealing treatment to room temperature.

[0037] Hot rolling and cold rolling treatment: The ingot that has undergone double-stage soaking annealing is hot rolled at 430°C into a 3mm plate with a total deformation of 90%, then cooled to room temperature and the plate is further cold rolled with a total deformation of 50%.

[0038] Double-stage solution treatment: Heat the cold-rolled plate to 450°C, keep it warm for 20 minutes, then continue to heat it to 480°C and keep it warm for 60 minutes.

[0039] Water quenching: The plate after solution treatment is water quenched to 25°C, and the transfer time from solution treatment to water quenching is 1 minute.

[0040] Double-stage aging treatment: heat the water-quenched plate to 125℃ for 300min, then heat to 150℃ for 1200min, and cool to room temperature.

[0041] Example 4

[0042] Double-stage soaking annealing treatment: first heat the ingot to 420°C and keep it warm for 1200 minutes; then continue to heat the ingot to 470°C and keep it warm for 1200 minutes; cool the ingot after the second-stage soaking annealing treatment to room temperature.

[0043] Hot rolling and cold rolling treatment: The ingot that has undergone double-stage soaking annealing is hot rolled at 410°C into a 2mm plate with a total deformation of 80%, then cooled to room temperature and the plate is further cold rolled with a total deformation of 60%.

[0044] Two-stage solution treatment: Heat the cold-rolled plate to 440°C, keep it warm for 10 minutes, then continue to heat it to 470°C and keep it warm for 120 minutes.

[0045] Water quenching: The plate after solution treatment is water quenched to 25°C, and the transfer time from solution treatment to water quenching is 5 minutes.

[0046] Three-stage aging treatment: heat the water-quenched plate to 100℃ and keep it for 1200min, then heat it to 160℃ and keep it for 60min, then cool it to 100℃ and keep it for 1200min, and then cool it to room temperature.

[0047] Example 5

[0048] Double-stage soaking annealing treatment: first heat the ingot to 430°C and keep it warm for 1500 minutes; then continue to heat the ingot to 470°C and keep it warm for 1200 minutes; cool the ingot after the second-stage soaking annealing treatment to room temperature.

[0049] Hot rolling and cold rolling treatment: The ingot that has undergone double-stage soaking annealing is hot rolled at 430°C into a 3mm plate with a total deformation of 80%, then cooled to room temperature and the plate is further cold rolled with a total deformation of 50%.

[0050] Double-stage solution treatment: Heat the cold-rolled plate to 450°C, keep it warm for 30 minutes, and then continue to heat it to 475°C and keep it warm for 90 minutes.

[0051] Water quenching: The plate after solution treatment is water quenched to 25°C, and the transfer time from solution treatment to water quenching is 10 minutes.

[0052] Three-stage aging treatment: heat the water-quenched plate to 125℃ for 300min, then heat to 200℃ for 10min, cool to 100℃ for 1200min, and then cool to room temperature.

[0053] Example 6

[0054] Double-stage soaking annealing treatment: first heat the ingot to 400°C and keep it warm for 1200 minutes; then continue to heat the ingot to 480°C and keep it warm for 1500 minutes; cool the ingot after the second-stage soaking annealing treatment to room temperature.

[0055] Hot rolling and cold rolling treatment: The ingot that has undergone double-stage soaking annealing is hot rolled at 420°C into a 3mm plate with a total deformation of 90%, then cooled to room temperature and the plate is further cold rolled with a total deformation of 60%.

[0056] Double-stage solution treatment: Heat the cold-rolled plate to 440°C, keep it warm for 40 minutes, and then continue to heat it to 470°C and keep it warm for 1200 minutes.

[0057] Water quenching: The plate after solution treatment is water quenched to 20°C, and the transfer time from solution treatment to water quenching is 6 minutes.

[0058] Three-stage aging treatment: heat the water-quenched plate to 110℃ for 1500min, then heat to 180℃ for 30min, cool to 120℃ for 1200min, and then cool to room temperature.

[0059] Comparative Examples 1 to 3 all use large-size 7075 aluminum alloy flat ingots as ingots, and the ingots are sequentially subjected to single-stage soaking annealing treatment, hot rolling treatment, single-stage solution treatment, water quenching and single-stage aging treatment.

[0060] Comparative Example 1

[0061] Single-stage soaking annealing treatment: heat the ingot from 25°C to 460°C for 1200 min, then cool to room temperature.

[0062] Hot rolling treatment: The ingot is hot rolled at 430°C into 3 mm plates.

[0063] Single-stage solution treatment: The hot-rolled plate is kept at 470°C for 120 minutes.

[0064] Water quenching: quench the plate after solution treatment to 25°C, and the transfer time from solution treatment to water quenching is 5 minutes.

[0065] Single-stage aging treatment: Heat the water-quenched plate to 120°C and keep it warm for 24 hours.

[0066] Comparative Example 2

[0067] Single-stage soaking annealing treatment: heat the ingot from 25°C to 470°C for 1800 min, and then cool to room temperature.

[0068] Hot rolling treatment: The ingot is hot rolled at 420°C into 1 mm plates.

[0069] Single-stage solution treatment: The hot-rolled plate is kept at 480°C for 60 minutes.

[0070] Water quenching: quench the plate after solution treatment to 30°C, and the transfer time from solution treatment to water quenching is 10 minutes.

[0071] Single-stage aging treatment: Heat the water-quenched plate to 150°C and keep it warm for 600 minutes.

[0072] Comparative Example 3

[0073] Single-stage soaking annealing treatment: heat the ingot directly from 25°C to 470°C, keep it at this temperature for 1500 min, and then cool it to room temperature.

[0074] Hot rolling treatment: The ingot is hot rolled at 420°C into 1 mm plates.

[0075] Single-stage solution treatment: The hot-rolled plate is kept at 480°C for 60 minutes.

[0076] Water quenching: The solution-treated plate is water quenched to 20°C, and the transfer time from solution-treated to water quenching is 20 minutes.

[0077] Single-stage aging treatment: Heat the water-quenched plate to 150°C and keep it warm for 60 minutes.

[0078] The tensile properties and electrical conductivity of the plates obtained in Examples 1 to 6 and Comparative Examples 1 to 3 were tested, and the properties are shown in Table 1.

[0079] Table 1:

[0080] Example Tensile strength(MPa) Yield strength (MPa) Elongation(%) Conductivity (%IACS) Example 1 591 557 11 31 Example 2 604 546 13 32 Example 3 605 557 12 30 Example 4 612 590 10 33 Example 5 623 600 9 34 Example 6 604 567 11 33 Comparative Example 1 545 456 11 28 Comparative Example 2 556 487 12 26 Comparative Example 3 543 432 13 27

[0081] By comparing the performance parameter values ​​of the embodiments and the comparative examples, it can be seen that the tensile strength, yield strength and electrical conductivity of the 7075 alloy sheet prepared by the combined treatment of two-stage soaking annealing, hot rolling deformation, cold rolling deformation, two-stage solid solution treatment, room temperature water quenching, two-stage or three-stage aging treatment are higher than those of the comparative example alloy.

Claims

1. A method for preparing a high-strength, ductile and high-conductivity 7075 alloy, characterized in that: The following steps are involved: S1, double-stage soaking annealing: the ingot is heated to the first-stage annealing temperature and kept warm to complete the first-stage soaking annealing; then the ingot is further heated to the second-stage annealing temperature and kept warm again to complete the second-stage soaking annealing, and the ingot is cooled to room temperature; S2, hot rolling deformation: the ingot cooled to room temperature is heated to the hot rolling temperature for hot rolling, the ingot is subjected to hot rolling deformation to obtain a plate, and the plate is cooled to room temperature; S3, cold rolling deformation: the cooled sheet is cold rolled, and the sheet undergoes cold rolling deformation; S4, two-stage solution treatment: the cold-rolled plate is heated to the first-stage solution temperature and kept warm; the plate is further heated to the second-stage solution temperature and kept warm again to complete the two-stage solution treatment; S5, room temperature water quenching: the plate after double-stage solution treatment is water quenched at room temperature; S6, double-stage aging or triple-stage aging treatment: The water-quenched plate is subjected to double-stage aging treatment or triple-stage aging treatment to obtain a high-strength, ductile and high-conductivity 7075 alloy.

2. The method for preparing the high-strength, ductile and high-conductivity 7075 alloy according to claim 1, characterized in that: In the S1, the first stage annealing temperature is 380°C to 450°C, and the holding time at the first stage annealing temperature is 300min to 1800min; the second stage annealing temperature is 460°C to 480°C, and the holding time at the second stage annealing temperature is 900min to 2400min.

3. The method for preparing the high-strength, ductile and high-conductivity 7075 alloy according to claim 1, characterized in that: In the S2, the hot rolling temperature is 400°C to 430°C, and the hot rolling deformation is 60% to 90%.

4. The method for preparing the high-strength, ductile and high-conductivity 7075 alloy according to claim 1, characterized in that: The cold rolling deformation in S3 is 60% to 90%.

5. The method for preparing the high-strength, ductile and high-conductivity 7075 alloy according to claim 1, characterized in that: In the S4, the first-stage solid solution temperature is 430°C to 450°C, and the holding time at the first-stage solid solution temperature is 10min to 60min; the second-stage solid solution temperature is 470°C to 480°C, and the holding time at the second-stage solid solution temperature is 60min to 180min.

6. The method for preparing the high-strength, ductile and high-conductivity 7075 alloy according to claim 1, characterized in that: The temperature of water during water quenching in S5 is ≤25°C, and the transition time from the end of the double-stage solid solution to the water quenching does not exceed 10 minutes.

7. The method for preparing the high-strength, ductile and high-conductivity 7075 alloy according to claim 1, characterized in that: The double-stage aging treatment in S6 is specifically as follows: heating the water-quenched plate to 100°C-125°C and keeping it warm for 300min-600min; then heating the plate to 130°C-170°C and keeping it warm for 300min-1800min to complete the double-stage aging treatment, and cooling the plate to room temperature to obtain a high-strength, ductile and high-conductivity 7075 alloy.

8. The method for preparing the high-strength, ductile and high-conductivity 7075 alloy according to claim 1, characterized in that: The three-stage aging treatment in S6 is specifically as follows: heating the water-quenched plate to 100°C-125°C and keeping it warm for 300min-600min; then heating the plate to 130°C-170°C and keeping it warm for 300min-1800min; finally, restoring the heating temperature of the plate to 100°C-125°C and keeping it warm for 1200min-1800min, completing the three-stage aging treatment, and cooling the plate to room temperature to obtain a high-strength, ductile and high-conductivity 7075 alloy.

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