Preparation method for improving mechanical property of 7-series aluminum alloy thick plate
By employing large-reduction rolling and a reasonable heat treatment process, the problem of insufficient core deformation in 7-series aluminum alloy thick plates was solved, thereby improving the mechanical properties of the plates and increasing production efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-23
- Publication Date
- 2026-03-20
AI Technical Summary
The existing rolling process for 7-series aluminum alloy thick plates is unreasonable, resulting in insufficient core deformation, low degree of residual phase fragmentation, impact on mechanical properties, low production efficiency, and long process flow.
By adopting a large reduction rolling method, combined with two-stage or multi-stage homogenization treatment, hot rolling treatment, solution treatment and two-stage aging treatment, and adjusting the hot rolling regime, the reduction per pass is gradually increased to promote the crushing and uniform distribution of residual phases and improve the degree of plastic deformation of the plate.
By using large-reduction rolling and reasonable heat treatment processes, the plastic deformation of the core of the plate is improved, the residual phase is more fully dissolved in the solution treatment, and more strengthening phase is precipitated, which significantly improves the mechanical properties and production efficiency of the plate.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of aluminum alloy deformation processing, in particular to a hot rolling and heat treatment method of 7-series aluminum alloy (Al-Zn-Mg-Cu series). BACKGROUND
[0002] 7-series (Al-Zn-Mg-Cu series) high-strength aluminum alloy is widely used in the fields of aerospace and rail transportation as a key structural material due to its high specific strength and specific stiffness, good plasticity, and low density.
[0003] With the large-scale and integration of aerospace vehicle structures, there is an increasing demand for high-strength 7-series aluminum alloy thick plates with excellent comprehensive performance. The preparation of thick plates is mainly completed by hot rolling. The traditional hot rolling process has a small pass reduction, and plastic deformation is mainly concentrated in the surface region of the plate, which cannot effectively penetrate into the interior of the plate, the core deformation is insufficient, the broken degree of residual phase is low, and the performance difference between the surface region and the core of the plate is large. In order to reduce the unevenness of the structure and performance, the total deformation amount usually needs to reach more than 80%. The 7-series aluminum alloy has high alloying degree, and as the thickness of the ingot increases, the risk of cracking increases. Under the existing casting technology conditions, the thickness of the ingot is difficult to increase significantly, and the thickness of the ingot is further reduced after milling, which leads to the problem of insufficient deformation when preparing thick plates, resulting in low core deformation of the plate, incomplete breaking of residual phase, and performance gap with the surface.
[0004] Therefore, in the prior art, the 7-series aluminum alloy thick plate has unreasonable rolling schedule, multiple rolling passes, long process flow, low production efficiency, and insufficient deformation in the core of the plate. The broken degree of residual phase (mainly S phase) after soaking is low, which leads to insufficient re-dissolution during solid solution treatment, affects the precipitation of strengthening phase during aging treatment, and further affects the mechanical properties of the finished plate.
[0005] Therefore, in the prior art, the 7-series aluminum alloy thick plate has unreasonable rolling schedule, multiple rolling passes, long process flow, low production efficiency, and insufficient deformation in the core of the plate. The broken degree of residual phase (mainly S phase) after soaking is low, which leads to insufficient re-dissolution during solid solution treatment, affects the precipitation of strengthening phase during aging treatment, and further affects the mechanical properties of the finished plate. SUMMARY
[0006] In order to solve the technical problem that the rolling process in the prior art is unreasonable, the degree of cumulative plastic deformation and the degree of structural fragmentation in the core of the plate are insufficient, and it is difficult to effectively improve the mechanical properties of the plate, the present invention provides a preparation method for improving the mechanical properties of 7-series aluminum alloy thick plates.
[0007] A method for improving the mechanical properties of 7-series aluminum alloy thick plates, specifically comprising the following steps:
[0008] Step 1: Based on the composition of 7-series aluminum alloys, aluminum ingots, Zn ingots, Mg ingots, cathode copper, AlZr3 master alloy, AlCu40 master alloy, AlMn20 master alloy, AlTi5B0.2A master alloy and AlTi6A master alloy are used as alloy raw materials for smelting and casting to obtain ingots.
[0009] Step 2: Homogenize the ingot described in Step 1 and mill its surface to obtain a homogenized ingot;
[0010] Step 3: Hot-roll the homogenized ingot from Step 2 to obtain the first plate with a thickness of 76mm~152mm;
[0011] Step 4: Perform solution treatment and pre-stretching treatment on the first sheet material from Step 3 to obtain the second sheet material;
[0012] Step 5: Perform aging treatment on the second sheet material from Step 4 to obtain a 7-series aluminum alloy thick plate, thus completing the process.
[0013] Furthermore, the homogenization process described in step two is a two-stage homogenization process, which includes a first-stage homogenization process performed sequentially at a temperature of 460℃~470℃ for 3h~6h and a second-stage homogenization process performed sequentially at a temperature of 475℃~480℃ for 15h~25h.
[0014] Furthermore, the two-stage homogenization process includes a first-stage homogenization process performed sequentially at a temperature of 468℃~470℃ for 4h~5h and a second-stage homogenization process performed at a temperature of 478℃~480℃ for 19h~21h.
[0015] Furthermore, the hot rolling process described in step three is carried out at a temperature of 420℃~450℃. The reduction per hot rolling pass increases with the number of passes. The deformation per single pass in the first 5 passes is 10mm~30mm, and the deformation per single pass from the 6th to the last pass is 30mm~50mm.
[0016] By increasing the reduction per pass, plastic deformation can penetrate deeper into the sheet metal, breaking down residual phases during the homogenization process, while simultaneously shortening the number of rolling passes and the overall process flow.
[0017] Furthermore, the hot rolling process described in step three is carried out at a temperature of 440℃~450℃.
[0018] Furthermore, the solution treatment in step four is a single-stage solution treatment, with a treatment temperature of 475℃~480℃ and a time of 3h~12h.
[0019] Furthermore, the deformation amount of the pre-stretching treatment in step four is 1%~3%, and the stretching speed is 10mm / s.
[0020] Furthermore, the aging process described in step five is a two-stage aging process, which includes a first-stage aging process with a temperature of 119℃~125℃ and a time of 4h~6h, and a second-stage aging process with a temperature of 161℃~165℃ and a time of 24h~30h.
[0021] Furthermore, the two-stage aging process includes a first-stage aging process performed sequentially at a temperature of 121℃~123℃ for 4h~6h and a second-stage aging process performed at a temperature of 162℃~163℃ for 24h~26h.
[0022] Furthermore, step five yields a 7-series aluminum alloy thick plate with a tensile strength of 500MPa~540MPa, a yield strength of 430MPa~480MPa, and an elongation of 10%~15%.
[0023] Beneficial effects of this invention:
[0024] This invention employs a high reduction rolling method, which effectively breaks down and evenly distributes the residual phase during the homogenization process, allowing for more complete redissolution during solution heat treatment. This increases the quantity and density of the strengthening phase (MgZn2) precipitated during aging heat treatment, thereby improving the mechanical properties of the sheet material.
[0025] By applying the technical solution of this invention, the hot rolling process is adjusted so that the reduction per pass gradually increases with the number of passes. In the first five passes, a smaller reduction (not exceeding 30 mm) is used to transform the casting structure in the billet into a deformed structure, improving the formability of the sheet and preventing cracking. As the casting structure transforms into a deformed structure, the sheet's machinability improves. From the sixth pass to the final pass, the reduction per pass gradually increases (30 mm to 50 mm), coupled with a smaller sheet thickness. The deformation rate increases with the number of rolling passes, effectively accumulating plastic deformation in the core of the sheet, resulting in a fully deformed structure, while simultaneously breaking down residual phases. The more thoroughly broken residual phases are smaller and more dispersed, leading to more complete re-dissolution of the residual phases (mainly S phase) during solution treatment. This increases the supersaturation of the sheet, promoting the precipitation of strengthening phases during aging treatment and improving the sheet's mechanical properties. By combining a higher initial rolling temperature with a larger single-pass reduction to generate more deformation heat, the sheet metal maintains a higher temperature during rolling, reducing temperature drop and promoting dynamic recrystallization and recovery. This releases stored deformation energy and helps suppress dynamic recrystallization during solution treatment, thereby improving sheet metal performance. This invention fully considers the deformation characteristics of 7-series aluminum alloy thick plates and the method's industrial applicability, making it highly operable and effective.
[0026] This invention is used to improve the mechanical properties of 7-series aluminum alloy thick plates. Attached Figure Description
[0027] Figure 1 This is a SEM image of the core structure of the aged sheet material in Example 2;
[0028] Figure 2 Here is a SEM image of the core structure of the aged sheet material in Comparative Example 2;
[0029] Figure 3 Metallographic photograph of the Cr acid core of the aged plate in Example 5;
[0030] Figure 4 This is a metallographic photograph of the Cr acid core of the aged plate in Example 2. Detailed Implementation
[0031] Specific Implementation Method 1: This implementation method describes a preparation method for improving the mechanical properties of 7-series aluminum alloy thick plates, specifically carried out according to the following steps:
[0032] Step 1: Based on the composition of 7-series aluminum alloys, aluminum ingots, Zn ingots, Mg ingots, cathode copper, AlZr3 master alloy, AlCu40 master alloy, AlMn20 master alloy, AlTi5B0.2A master alloy and AlTi6A master alloy are used as alloy raw materials for smelting and casting to obtain ingots.
[0033] Step 2: Homogenize the ingot described in Step 1 and mill its surface to obtain a homogenized ingot;
[0034] Step 3: Hot-roll the homogenized ingot from Step 2 to obtain the first plate with a thickness of 76mm~152mm;
[0035] Step 4: Perform solution treatment and pre-stretching treatment on the first sheet material from Step 3 to obtain the second sheet material;
[0036] Step 5: Perform aging treatment on the second sheet material from Step 4 to obtain a 7-series aluminum alloy thick plate, thus completing the process.
[0037] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the homogenization process in step two is a two-stage homogenization process. The two-stage homogenization process includes a first-stage homogenization process performed sequentially at a temperature of 460℃~470℃ for 3h~6h, and a second-stage homogenization process performed at a temperature of 475℃~480℃ for 15h~25h. Everything else is the same as in Specific Implementation Method One.
[0038] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the two-stage homogenization process includes a first-stage homogenization process performed sequentially at a temperature of 468℃~470℃ for 4h~5h, and a second-stage homogenization process performed at a temperature of 478℃~480℃ for 19h~21h. Everything else is the same as in Specific Implementation Method One or Two.
[0039] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the hot rolling process described in step three is carried out at a temperature of 420℃~450℃. The reduction per hot rolling pass increases with the number of passes. The deformation per pass in the first 5 passes is 10mm~30mm, and the deformation per pass from the 6th to the last pass is 30mm~50mm. Everything else is the same as in Specific Implementation Methods One to Three.
[0040] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the hot rolling process described in step three is carried out at a temperature of 440℃~450℃. Everything else is the same as in Specific Implementation Methods One to Four.
[0041] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the solution treatment in step four is a single-stage solution treatment, with a treatment temperature of 475℃~480℃ and a time of 3h~12h. Everything else is the same as in Specific Implementation Methods One to Five.
[0042] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the deformation amount of the pre-stretching treatment in step four is 1% to 3%, and the stretching speed is 10 mm / s. Everything else is the same as in Specific Implementation Methods One to Six.
[0043] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the aging process described in step five is a two-stage aging process. The two-stage aging process includes a first-stage aging process performed sequentially at a temperature of 119℃~125℃ for 4h~6h, and a second-stage aging process performed at a temperature of 161℃~165℃ for 24h~30h. Everything else is the same as in Specific Implementation Methods One to Seven.
[0044] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the two-stage aging process includes a first-stage aging process at a temperature of 121℃~123℃ for 4h~6h, followed by a second-stage aging process at a temperature of 162℃~163℃ for 24h~26h. Everything else is the same as in Specific Implementation Methods One to Eight.
[0045] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that the tensile strength of the 7-series aluminum alloy thick plate obtained in step five is 500MPa~540MPa, the yield strength is 430MPa~480MPa, and the elongation is 10%~15%. Everything else is the same as in Specific Implementation Methods One to Nine.
[0046] The scope of this invention is not limited to the above-described embodiments; a combination of one or more specific embodiments can also achieve the purpose of the invention.
[0047] Example 1:
[0048] This embodiment describes a method for improving the mechanical properties of 7050 aluminum alloy thick plates, which is carried out according to the following steps:
[0049] Step 1: Based on the alloy composition, 99.95 grade aluminum ingots, Zn ingots, Mg ingots, cathode copper, AlZr3 master alloy, AlCu40 master alloy, AlMn20 master alloy, AlTi5B0.2A master alloy and AlTi6A master alloy are used as alloy raw materials for smelting and casting to obtain ingots.
[0050] Step 2: The ingot described in Step 1 is subjected to a two-stage homogenization treatment under slow heating conditions. The first stage homogenization treatment temperature is 470℃ and the time is 5h; the second stage homogenization treatment temperature is 480℃ and the time is 20h. After the homogenization treatment is completed, the ingot is removed from the furnace and air-cooled. After natural cooling, the surface is milled to 480mm to obtain a homogenized ingot.
[0051] Step 3: Heat the homogenized ingot from Step 2 to 440℃ and hold for 8 hours. Then hot roll it. During the rolling process, the reduction per pass gradually increases to obtain the first plate with a thickness of 152mm. The specific rolling process is shown in Table 1.
[0052] Step 4: The first plate from Step 3 is subjected to solution treatment at a temperature of 477℃ for 6.5 hours, followed immediately by quenching. The solution treatment and quenching are performed in a roller hearth furnace with water as the quenching medium. The plate after solution and quenching is then subjected to pre-stretching at a deformation rate of 2% and a stretching speed of 10 mm / s to obtain the second plate.
[0053] Step 5: Perform a two-stage aging treatment on the second plate material from Step 4. The first stage of aging treatment is carried out at a temperature of 121℃ for 5 hours; the second stage of aging treatment is carried out at a temperature of 163℃ for 24 hours, resulting in a 7050-T7451 aluminum alloy thick plate, thus completing the process.
[0054] Example 2:
[0055] This embodiment describes a method for improving the mechanical properties of 7050 aluminum alloy thick plates, which is carried out according to the following steps:
[0056] Step 1: Based on the alloy composition, 99.95 grade aluminum ingots, Zn ingots, Mg ingots, cathode copper, AlZr3 master alloy, AlCu40 master alloy, AlMn20 master alloy, AlTi5B0.2A master alloy and AlTi6A master alloy are used as alloy raw materials for smelting and casting to obtain ingots.
[0057] Step 2: The ingot described in Step 1 is subjected to a two-stage homogenization treatment under slow heating conditions. The first stage homogenization treatment temperature is 470℃ and the time is 5h; the second stage homogenization treatment temperature is 480℃ and the time is 25h. After the homogenization treatment is completed, the ingot is removed from the furnace and air-cooled. After natural cooling, the surface is milled to 480mm to obtain a homogenized ingot.
[0058] Step 3: Heat the homogenized ingot from Step 2 to 430℃ and hold for 6 hours. Then hot roll it. During the rolling process, the reduction per pass gradually increases to obtain the first plate with a thickness of 127mm. See Table 1 for the specific rolling process.
[0059] Step 4: The first plate from Step 3 is subjected to solution treatment at a temperature of 479°C for 8 hours, followed immediately by quenching. The solution treatment and quenching are performed in a roller hearth furnace with water as the quenching medium. The plate after solution and quenching is then subjected to pre-stretching at a deformation rate of 2% and a stretching speed of 10 mm / s to obtain the second plate.
[0060] Step 5: Perform a two-stage aging treatment on the second plate material from Step 4. The first stage of aging treatment is carried out at a temperature of 121℃ for 5 hours; the second stage of aging treatment is carried out at a temperature of 163℃ for 24 hours, resulting in a 7050-T7451 aluminum alloy thick plate, thus completing the process.
[0061] Example 3:
[0062] This embodiment describes a method for improving the mechanical properties of 7050 aluminum alloy thick plates, which is carried out according to the following steps:
[0063] Step 1: Based on the alloy composition, 99.95 grade aluminum ingots, Zn ingots, Mg ingots, cathode copper, AlZr3 master alloy, AlCu40 master alloy, AlMn20 master alloy, AlTi5B0.2A master alloy and AlTi6A master alloy are used as alloy raw materials for smelting and casting to obtain ingots.
[0064] Step 2: The ingot described in Step 1 is subjected to a two-stage homogenization treatment under slow heating conditions. The first stage homogenization treatment temperature is 470℃ and the time is 5h; the second stage homogenization treatment temperature is 480℃ and the time is 25h. After the homogenization treatment is completed, the ingot is removed from the furnace and air-cooled. After natural cooling, the surface is milled to 440mm to obtain a homogenized ingot.
[0065] Step 3: Heat the homogenized ingot from Step 2 to 440℃ and hold for 8 hours. Then hot roll it. During the rolling process, the reduction per pass gradually increases to obtain the first plate with a thickness of 76mm. See Table 1 for the specific rolling process.
[0066] Step 4: The first plate from Step 3 is subjected to solution treatment at a temperature of 479℃ for 6.3 hours, followed immediately by quenching. The solution treatment and quenching are performed in a roller hearth furnace with water as the quenching medium. The plate after solution and quenching is then subjected to pre-stretching at a deformation rate of 2% and a stretching speed of 10 mm / s to obtain the second plate.
[0067] Step 5: Perform a two-stage aging treatment on the second plate material from Step 4. The first stage of aging treatment is carried out at a temperature of 121℃ for 6 hours; the second stage of aging treatment is carried out at a temperature of 162℃ for 28 hours, resulting in a 7050-T7451 aluminum alloy thick plate, thus completing the process.
[0068] Example 4:
[0069] The difference between this embodiment and Embodiment 2 is that step five, the two-stage aging treatment, is as follows: the first-stage aging treatment temperature is 121℃ and the time is 6 hours; the second-stage aging treatment temperature is 163℃ and the time is 24 hours, resulting in a 7050-T7451 aluminum alloy thick plate. The other steps are the same as in Embodiment 2.
[0070] Example 5:
[0071] The difference between this embodiment and embodiment 2 is that:
[0072] Step 3: Heat the homogenized ingot from Step 2 to 440℃ and hold for 8 hours. Then hot roll it. During the rolling process, the reduction per pass gradually increases to obtain the first plate with a thickness of 127mm. See Table 1 for the specific rolling process.
[0073] Step 4: The first plate from Step 3 is subjected to solution treatment at a temperature of 477℃ for 8 hours, followed immediately by quenching. The solution treatment and quenching are carried out in a roller hearth furnace with water as the quenching medium. The plate after solution treatment and quenching is then subjected to pre-stretching at a deformation rate of 2% and a stretching speed of 10 mm / s to obtain the second plate.
[0074] The other steps are the same as in Example 2.
[0075] Comparative Example 1
[0076] A method for preparing 7050 aluminum alloy thick plates, the process steps are as follows:
[0077] Step 1: Based on the alloy composition, 99.95 grade aluminum ingots, Zn ingots, Mg ingots, cathode copper, AlZr3 master alloy, AlCu40 master alloy, AlMn20 master alloy, AlTi5B0.2A master alloy and AlTi6A master alloy are used as alloy raw materials for smelting and casting to obtain ingots.
[0078] Step 2, Homogenization Treatment of Ingots: Under slow heating conditions, the ingots obtained in Step 1 are subjected to three-stage homogenization treatment. The first stage homogenization treatment temperature is 400℃ and the time is 12h; the second stage homogenization treatment temperature is 470℃ and the time is 40h; the third stage homogenization treatment temperature is 480℃ and the time is 20h. After the homogenization treatment is completed, the ingots are removed from the furnace and air-cooled. After natural cooling, the surface is milled to 485mm to obtain homogenized ingots.
[0079] Step 3, Plate rolling: The homogenized ingot is heated to 420℃ and held for 6 hours, and then hot rolled. The reduction per pass during the rolling process is shown in Table 1. The first plate with a thickness of 152mm is obtained.
[0080] Step 4: Solution quenching and pre-stretching: The first plate is solution quenched at 479℃ for 9 hours, followed immediately by quenching. The solution quenching and pre-stretching are carried out in a roller hearth furnace with water as the quenching medium. The plate after solution quenching is then pre-stretched with a pre-stretching deformation of 2% and a stretching speed of 10 mm / s to obtain the second plate.
[0081] Step 5, Aging Treatment: The second plate is subjected to a two-stage aging treatment. The first stage of aging treatment is carried out at a temperature of 121℃ for 4 hours; the second stage of aging treatment is carried out at a temperature of 163℃ for 24 hours, resulting in 7050-T7451 pre-stretched thick plate.
[0082] Comparative Example 2
[0083] A method for preparing 7050 aluminum alloy thick plates, the process steps are as follows:
[0084] Step 1: Based on the alloy composition, 99.95 grade aluminum ingots, Zn ingots, Mg ingots, cathode copper, AlZr3 master alloy, AlCu40 master alloy, AlMn20 master alloy, AlTi5B0.2A master alloy and AlTi6A master alloy are used as alloy raw materials for smelting and casting to obtain ingots.
[0085] Step 2, Homogenization Treatment of Ingots: Under slow heating conditions, the ingots obtained in Step 1 are subjected to three-stage homogenization treatment. The first stage homogenization treatment temperature is 400℃ and the time is 12h; the second stage homogenization treatment temperature is 470℃ and the time is 40h; the third stage homogenization treatment temperature is 480℃ and the time is 20h. After the homogenization treatment is completed, the ingots are removed from the furnace and air-cooled. After natural cooling, the surface is milled to 485mm to obtain homogenized ingots.
[0086] Step 3, Plate rolling: The homogenized ingot is heated to 430℃ and held for 8 hours, and then hot rolled. The reduction per pass during the rolling process is shown in Table 1. The first plate with a thickness of 127mm is obtained.
[0087] Step 4: Solution quenching and pre-stretching treatment: The first plate is solution quenched at 477℃ for 8 hours, followed immediately by quenching. The solution quenching and quenching treatments are carried out in a roller hearth furnace with water as the quenching medium. The plate after solution quenching is then pre-stretched with a pre-stretching deformation of 2% and a stretching speed of 10 mm / s to obtain the second plate.
[0088] Step 5, Aging Treatment: The second plate is subjected to a two-stage aging treatment. The first stage of aging treatment is carried out at a temperature of 120℃ for 3 hours; the second stage of aging treatment is carried out at a temperature of 165℃ for 19 hours, resulting in 7050-T7451 pre-stretched thick plate.
[0089] Comparative Example 3
[0090] A method for preparing 7050 aluminum alloy thick plates:
[0091] The difference between this comparative example and Example 3 is:
[0092] Step 2, Homogenization Treatment of Ingots: Under slow heating conditions, the ingots obtained in Step 1 are subjected to three-stage homogenization treatment. The first stage homogenization treatment temperature is 400℃ and the time is 12h; the second stage homogenization treatment temperature is 470℃ and the time is 40h; the third stage homogenization treatment temperature is 480℃ and the time is 20h. After the homogenization treatment is completed, the ingots are removed from the furnace and air-cooled. After natural cooling, the surface is milled to 485mm to obtain homogenized ingots.
[0093] Step 3, Plate rolling: The homogenized ingot is heated to 440℃ and held for 8 hours, and then hot rolled. The reduction per pass during the rolling process is shown in Table 1. The first plate with a thickness of 76mm is obtained.
[0094] The other steps are the same as in Example 3.
[0095] Table 1
[0096]
[0097] The mechanical properties of the plates were sampled from the core of the plates. The longitudinal mechanical properties (yield strength, tensile strength and elongation) of the aluminum alloy thick plates obtained in each example and comparative example were tested in accordance with GB / T 228.1-2010 "Metallic materials - Tensile testing - Part 1: Test method at room temperature". The test results are shown in Table 2.
[0098] Table 2
[0099]
[0100] Figure 1 This is a SEM image of the core structure of the aged sheet material in Example 2; Figure 2 The image shows the SEM microstructure of the core of the aged sheet in Comparative Example 2. It can be seen that after using the large-scale hot rolling process with reduced pressure, the residual phase in the sheet is fully broken down, and the re-dissolution during the solution treatment process is more complete. The residual phase content and size in this example are superior to those in the comparative example, resulting in more complete aging of the final sheet and achieving better mechanical properties.
[0101] Figure 3 Metallographic photograph of the Cr acid core of the aged plate in Example 5; Figure 4 The image shows a metallographic photograph of the Cr acid core of the aged sheet material in Example 2. It can be seen that after employing the hot rolling process with this reduction, the residual phase is more thoroughly broken down, and the number of coarse residual phases serving as nucleation sites for recrystallization is reduced, which is beneficial for recrystallization control.
[0102] As can be seen from the above description, for plates with thicknesses of 76mm, 127mm and 152mm, the hot rolling process of the above embodiments of the present invention has a large single-pass deformation, a shorter rolling process, and a lower temperature drop after rolling, which improves rolling efficiency and enhances the core mechanical properties of the plate.
Claims
1. A method for preparing thick plates of 7-series aluminum alloy with improved mechanical properties, characterized in that... This method is specifically carried out in the following steps: Step 1: Based on the composition of 7-series aluminum alloys, aluminum ingots, Zn ingots, Mg ingots, cathode copper, AlZr3 master alloy, AlCu40 master alloy, AlMn20 master alloy, AlTi5B0.2A master alloy and AlTi6A master alloy are used as alloy raw materials for smelting and casting to obtain ingots. Step 2: Homogenize the ingot described in Step 1 and mill its surface to obtain a homogenized ingot; Step 3: Hot-roll the homogenized ingot from Step 2 to obtain the first plate with a thickness of 76mm~152mm; Step 4: Perform solution treatment and pre-stretching treatment on the first sheet material from Step 3 to obtain the second sheet material; Step 5: Perform aging treatment on the second sheet material from Step 4 to obtain a 7-series aluminum alloy thick plate, thus completing the process.
2. The method for preparing a thick plate of 7-series aluminum alloy with improved mechanical properties according to claim 1, characterized in that... The homogenization process described in step two is a two-stage homogenization process, which includes a first-stage homogenization process performed at a temperature of 460℃~470℃ for 3h~6h and a second-stage homogenization process performed at a temperature of 475℃~480℃ for 15h~25h.
3. The method for preparing a thick plate of 7-series aluminum alloy with improved mechanical properties according to claim 2, characterized in that... The two-stage homogenization process includes a first-stage homogenization process performed at a temperature of 468℃~470℃ for 4h~5h, followed by a second-stage homogenization process performed at a temperature of 478℃~480℃ for 19h~21h.
4. The preparation method for improving the mechanical properties of 7-series aluminum alloy thick plates according to claim 1, characterized in that... The hot rolling process described in step three is carried out at a temperature of 420℃~450℃. The reduction per hot rolling pass increases with the number of passes. The deformation per single pass in the first 5 passes is 10mm~30mm, and the deformation per single pass from the 6th to the last pass is 30mm~50mm.
5. The method for preparing a thick plate of 7-series aluminum alloy with improved mechanical properties according to claim 4, characterized in that... The hot rolling process described in step three is carried out at a temperature of 440℃~450℃.
6. The method for preparing a thick plate of 7-series aluminum alloy with improved mechanical properties according to claim 1, characterized in that... Step four involves a single-stage solution treatment at a temperature of 475℃ to 480℃ for 3 to 12 hours.
7. The method for preparing a thick plate of 7-series aluminum alloy with improved mechanical properties according to claim 1, characterized in that... The deformation amount of the pre-stretching treatment in step four is 1%~3%, and the stretching speed is 10mm / s.
8. The method for preparing a thick plate of 7-series aluminum alloy with improved mechanical properties according to claim 1, characterized in that... The aging process described in step five is a two-stage aging process, which includes a first-stage aging process with a temperature of 119℃~125℃ and a time of 4h~6h, and a second-stage aging process with a temperature of 161℃~165℃ and a time of 24h~30h.
9. A method for preparing thick plates of 7-series aluminum alloys with improved mechanical properties according to claim 8, characterized in that... The two-stage aging process includes a first-stage aging process with a temperature of 121℃~123℃ and a time of 4h~6h, followed by a second-stage aging process with a temperature of 162℃~163℃ and a time of 24h~26h.
10. The method for preparing a thick plate of 7-series aluminum alloy with improved mechanical properties according to claim 1, characterized in that... Step 5 yields a 7-series aluminum alloy thick plate with a tensile strength of 500MPa~540MPa, a yield strength of 430MPa~480MPa, and an elongation of 10%~15%.