Preparation process and application of 7055 plate

Abstract

The invention discloses a preparation technology and application of a 7055 plate. The preparation technology comprises the following steps that S1, a 7055 aluminum alloy ingot blank prepared through a spray forming technology is preheated; s2, the preheated aluminum alloy ingot blank is subjected to hot rolling, solid solution and quenching after cooling, and the grain size of the 7055 aluminum alloy ingot blank prepared through the spray forming process is 1t; the second phase area fraction is less than lt; and 10%. According to the preparation technology of the 7055 plate, an ingot blank is prepared through a spray forming method, Fe-rich phase particles in alloy are reduced, and the ingot blank does not need to be subjected to homogenization heat treatment; equiaxed grains are formed in the solid solution process of the hot-rolled plate, so that the anisotropy of the plate is reduced, only single-stage heat treatment is needed subsequently, and two-stage or multi-stage aging heat treatment is not needed. The reduction of the Fe-rich phase and the formation of equiaxed grains play a significant role in improving the anisotropy of the alloy.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloys, and in particular to a preparation process and application of a 7055 plate. Background Art

[0002] 7055 aluminum alloy is a high alloy alloy with high specific strength, strong plastic deformation ability and good machinability, and is widely used in the aerospace industry. 7055 aluminum alloy sheet is an important product of the alloy. As a structural material, it is widely used in military and civilian equipment. It is the main material for preparing fuselage panels and wing skins of fighter jets and large passenger aircraft, and has high market demand and economic value.

[0003] At present, the main methods for preparing 7055 aluminum alloy sheets are extrusion and rolling. Among them, due to the limitations of extrusion production equipment, the width of the produced sheets is small and the thickness is large, while the rolling process can mass-produce thin sheets of large width, with a wider product size range and higher production efficiency. However, 7XXX aluminum alloy sheets produced by rolling technology often have anisotropy problems, that is, there are significant differences in the mechanical properties of the sheet in the rolling direction (0° direction), the rolling direction and the transverse centerline (45° direction) and the transverse direction (90° direction). The anisotropy of the mechanical properties of the sheet is mainly affected by factors such as texture, grain morphology, type and size of the second phase. The 7055 aluminum alloy produced by melting and casting is usually subjected to homogenization heat treatment at a temperature above 450°C and for 24 hours before hot deformation. This process will precipitate Al3Zr particles. These particles affect the subsequent recrystallization behavior of the plate by pinning dislocations, which is not conducive to complete recrystallization, resulting in obvious deformation texture in the plate and different grain sizes in all directions, which leads to differences in mechanical properties in all directions of the plate. In addition, there are more Fe-rich second phases in the 7055 aluminum alloy produced by melting and casting. These Fe-rich phases are not easy to be eliminated in subsequent heat treatment. During the rolling process, they are streamlined and distributed along the rolling direction, which also has a significant effect on the anisotropy of the rolled plate. In order to improve the anisotropy of aluminum alloy rolled plates, the methods of regulating the rolling process and optimizing the solid solution and aging heat treatment are usually adopted. For example, cross rolling can make the alloy grains small and uniform, improve the uniformity of the alloy structure and reduce anisotropy, but this method is difficult to apply to the production of large-size rolled plates; reducing the rolling deformation can also reduce the anisotropy of the mechanical properties of aluminum alloy plates, but the actual production process often requires a deformation greater than 80%, so it is also difficult to reduce anisotropy by controlling the rolling deformation. The three-stage solid solution (450℃×2h)+(465℃×1h)+(475℃×1.5h) and three-stage aging treatment (120℃×24h)+(175℃×1.5h)+(120℃×24h) method can reduce the anisotropy of 7055 aluminum alloy, but there are still many Fe-rich phases in the alloy after the three-stage solid solution, and the use of three-stage solid solution and three-stage aging heat treatment will greatly increase the process difficulty and production cost. In addition, the use of double-stage aging can reduce the difference in mechanical properties in each direction of the rolled plate, but double-stage aging will reduce the strength of the alloy, making it difficult to prepare plates with a strength greater than 600MPa.

[0004] Therefore, there is an urgent need to provide a high-strength, low-anisotropy plate process with a strength greater than 600 MPa, an elongation greater than 10%, and a plane anisotropy index IPA < 5%. Summary of the invention

[0005] The present invention aims to solve the above technical problems existing in the prior art. To this end, the present invention proposes a preparation process of 7055 plate, which adopts a spray forming method to prepare an ingot, reduces Fe-rich phase particles in the alloy, and the ingot does not need to be homogenized heat treated; the hot-rolled plate forms equiaxed grains during the solid solution process, thereby reducing the anisotropy of the plate, and only single-stage heat treatment is required subsequently, without double-stage or multi-stage aging heat treatment. The reduction of Fe-rich phase and the formation of equiaxed grains have a significant effect on improving the anisotropy of the alloy.

[0006] The invention also proposes an application of a preparation process of a 7055 plate in the preparation of aerospace components or automobile components.

[0007] According to one aspect of the present invention, a preparation process of 7055 sheet is proposed, comprising the following steps:

[0008] S1. Preheating the 7055 aluminum alloy ingot prepared by the spray forming process;

[0009] S2. The preheated aluminum alloy ingot is hot rolled, cooled, solutionized, and quenched;

[0010] The grain size of the 7055 aluminum alloy ingot prepared by the spray forming process is less than 100 μm, and the area fraction of the second phase is less than 10%.

[0011] The beneficial effects of the present invention are as follows:

[0012] The present invention adopts a spray forming process to prepare the ingot, and its cooling rate is faster than that of the traditional smelting and casting ingot, which inhibits the atomic diffusion during the solidification process, so that the area fraction of the second phase particles in the ingot is less than 10%, which is significantly reduced compared with the second phase area fraction in the traditional smelting and casting alloy ingot, and has a significant effect on improving the mechanical properties and anisotropy of the subsequent plate; the ingot does not need to be subjected to a long-term homogenization heat treatment above 450°C before hot rolling, which can effectively shorten the production process and save production costs; preheating before hot rolling allows the ingot to reach the thermal deformation temperature, which helps to eliminate the soluble second phase in the ingot and improve the thermal deformation ability of the plate; under the hot rolling condition, the temperature of the 7055 aluminum alloy is higher than the recrystallization temperature, so dynamic recrystallization occurs to form a recrystallized structure; at the same time, the method can make the plate deform by deformation Continuously generating stored energy provides a driving force for the dynamic recrystallization of the plate, thereby forming initial recrystallized grains; cooling after rolling is completed helps to inhibit the precipitation of the second phase during the cooling process of the plate, which is beneficial to obtaining a supersaturated solid solution in the subsequent solution heat treatment process; solid solution, on the one hand, can form a supersaturated solid solution, and on the other hand, can make the recrystallized grains formed during the deformation process grow and form equiaxed grains, thereby improving the anisotropy of the plate; quenching after solid solution is completed is beneficial to ensure the supersaturation of the plate, which is beneficial to the diffusion of atoms in the subsequent aging process and the formation of fine and dispersed strengthening phases, thereby achieving the effect of improving the strength; this method is suitable for the production of large-size, high-strength, low-anisotropy thin plates of 7055 aluminum alloy. The production process does not require homogenization and multi-stage aging. The process flow is simple and the cost is low, which is conducive to large-scale industrial preparation.

[0013] In some embodiments of the present invention, in step S1, a 7055 aluminum alloy ingot is prepared by a spray forming method, and the main alloy components are: Si < 0.10%, Fe < 0.15%, Cu = 2.0-2.6%, Mg = 1.8-2.3%, Zn = 7.6-8.4%, Zr = 0.08-0.25%. The smelting raw materials are high-purity Al, pure Zn, pure Mg, and intermediate alloys such as Al-Cu and Al-Zr. The ingredients are prepared according to the alloy component ratio and considering the burning loss. The smelting temperature is 700-760°C, and then the molten metal is spray-deposited, and the protective gas is industrial nitrogen. The ingot with a diameter of 25-35cm is collected on the deposition plate.

[0014] In some embodiments of the present invention, in step S1, the preheating step is to maintain the temperature at 400-450°C for 2-8 hours.

[0015] Preheating is performed at 400-450°C for a short time to allow the ingot to reach the thermal deformation temperature, which helps to eliminate the soluble second phase in the ingot and improve the thermal deformation capacity of the plate.

[0016] In some embodiments of the present invention, in step S2, the hot rolling temperature is 420-450°C.

[0017] The hot rolling temperature is maintained at 420-450°C, and the plate temperature is higher than the recrystallization temperature of the 7055 aluminum alloy, so dynamic recrystallization occurs to form a recrystallized structure; the rolling process adopts continuous multi-pass rolling, without the need for intermediate annealing and subsequent cold rolling, to ensure that the plate has good deformation ability during the deformation process. At the same time, this method can enable the plate to continuously generate energy storage through deformation, providing a driving force for the dynamic recrystallization of the plate, thereby forming initial recrystallized grains.

[0018] In some embodiments of the present invention, in step S2, the cooling method includes water cooling.

[0019] Rapid water cooling after hot rolling helps to inhibit the precipitation of the second phase during the cooling process of the plate, which is beneficial to obtaining a supersaturated solid solution in the subsequent solution heat treatment process.

[0020] In some embodiments of the present invention, in step S2, the temperature of the rolled plate after hot rolling is not less than 420°C.

[0021] In some embodiments of the present invention, in step S2, the hot rolling is performed for 7 to 9 passes.

[0022] In some embodiments of the present invention, in step S2, the deformation amount per pass is 10-15%.

[0023] In some embodiments of the present invention, in step S2, the total deformation amount of the hot rolling is 80-90%.

[0024] In some embodiments of the present invention, in step S2, the total deformation amount of the hot rolling is 85-90%.

[0025] In some embodiments of the present invention, in step S2, the temperature of the solid solution is 400-480° C., and the time of the solid solution is 1-6 hours.

[0026] By adopting solid solution at 400-480°C, on the one hand, a supersaturated solid solution can be formed, and on the other hand, the high temperature can make the recrystallized grains formed during the deformation process grow and form equiaxed grains, thereby improving the anisotropy of the plate.

[0027] In some embodiments of the present invention, in step S2, the solution temperature is 450-490° C., and the solution time is 1-3 hours.

[0028] In some embodiments of the present invention, in step S2, the quenching method includes water-cooling quenching.

[0029] In some embodiments of the present invention, in step S2, the quenching transfer time is no longer than 20 s.

[0030] After the solution treatment is completed, room temperature water quenching is used, and the quenching transfer time is controlled to be less than 20s, which is beneficial to ensure the supersaturation of the plate and to facilitate the expansion of atoms and the formation of fine and dispersed strengthening phases in the subsequent aging process, thereby improving the strength.

[0031] In some embodiments of the present invention, in step S2, aging treatment is also included after quenching.

[0032] In some embodiments of the present invention, in step S2, the temperature of the aging treatment is 100 to 130° C., and the time of the aging treatment is 16 to 28 hours.

[0033] The aging process adopts single-stage aging, and the temperature is controlled at 100-130°C, which is conducive to obtaining the highest strength. There is no need for double-stage or multi-stage aging in this process, which effectively reduces the production process and cost. This method is suitable for the production of large-size, high-strength, low-anisotropy thin plates of 7055 aluminum alloy. The production process does not require homogenization and multi-stage aging. The process flow is simple, the cost is low, and it is conducive to large-scale industrial preparation.

[0034] In some embodiments of the present invention, in step S2, the temperature of the aging treatment is 115-125° C., and the time of the aging treatment is 16-28 hours.

[0035] The sheet material prepared by the present invention has the characteristics of grain size <100 μm, and area fraction of coarse iron-rich phase particles <1%. At the same time, the sheet material prepared by the present invention has the properties of tensile strength greater than 600 MPa in the directions of 0°, 45° and 90°, elongation >10%, and plane anisotropy index IPA <5%.

[0036] According to two aspects of the present invention, a process for preparing the 7055 sheet material is proposed for use in preparing aerospace components or automobile components. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a SEM photograph of the spray-formed 7055 aluminum alloy ingot of Example 1;

[0038] Figure 2 is a SEM photograph of the ingot after being kept at 430° C. for 6 hours in Example 1;

[0039] Figure 3 This is a metallographic photograph of the hot-rolled plate after solution treatment in Example 1;

[0040] Figure 4 This is a SEM photo of the hot-rolled plate after aging treatment in Example 1;

[0041] Figure 5 This is a TEM photo of the hot-rolled plate after aging treatment in Example 1;

[0042] Figure 6 The engineering stress-strain curves of the hot-rolled plate in Example 1 stretched along the directions of 0°, 45° and 90° after aging treatment;

[0043] Figure 7 This is a TEM photo of the hot-rolled plate in Comparative Example 1 after homogenization heat treatment;

[0044] Figure 8 This is a metallographic photograph of the hot-rolled plate after solution treatment in Comparative Example 1;

[0045] Fig. 9 This is a metallographic photograph of the hot-rolled plate after solution heat treatment in Comparative Example 2;

[0046] Fig.10 This is a TEM photo of the hot-rolled plate of Comparative Example 2 after double-stage aging treatment. DETAILED DESCRIPTION

[0047] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0048] Example 1

[0049] This embodiment prepares a spray-formed 7055 aluminum alloy high-strength and low-anisotropy plate, and the specific implementation steps are as follows:

[0050] S1. A 7055 aluminum alloy ingot is prepared by a spray forming method, wherein the main alloy components are: Si < 0.10%, Fe < 0.15%, Cu = 2.0%, Mg = 1.8%, Zn = 7.8%, Zr = 0.08%, and the smelting raw materials are high-purity Al, pure Zn, pure Mg, and intermediate alloys such as Al-Cu and Al-Zr. The ingredients are prepared according to the alloy component ratio and considering the burning loss. The smelting temperature is 700-760°C, and the molten metal is then spray-deposited. The protective gas is industrial nitrogen. The 7055 aluminum alloy ingot with an average grain size of 45.8μm and a second phase area fraction of 6.2% is collected on a deposition plate with a diameter of 25-35cm;

[0051] S2. Cut the ingot with the size of 200mm*150mm*10mm, without homogenization heat treatment, and keep it at 430℃ for 6h before extrusion to reduce the residual phase particles in the ingot;

[0052] S3. The ingot after heat preservation is hot rolled, the initial rolling temperature is 450°C, and the plate is rolled from 10 mm to 2 mm in 8 passes, the deformation amount of each rolling is 10 to 20%, and the temperature after rolling is 420°C, so that the plate undergoes dynamic recrystallization during the thermal deformation process, and the hot-rolled plate is water-cooled;

[0053] S4. Use an air heating furnace to perform a solution heat treatment at 450℃ / 1h+473℃ / 1h on the hot-rolled plate, so that the plate undergoes complete recrystallization during the solution process, and then quenches in room temperature water with a quenching transfer time of 10s. After quenching, place the plate in an oil bath furnace at 120℃ for aging treatment within 1min, and the aging time is 22h;

[0054] Figure 1 The SEM photograph of the spray-formed 7055 aluminum alloy ingot used in this method shows that the average grain size is about 45.8μm and the residual phase area fraction is 6.2%.

[0055] Figure 2 This is a SEM photograph of the ingot after being kept at 430℃ for 6h. It can be seen that most of the residual phase is dissolved, leaving only a small amount of insoluble Fe-rich phase particles, with an area fraction of about 0.66%.

[0056] Figure 3 This is a metallographic photograph of the hot-rolled plate after solution treatment. It can be seen that the grains in the plate are equiaxed recrystallized grains with an average grain size of 35.8μm.

[0057] Figure 4 This is a SEM photo of the hot-rolled plate after aging treatment. It can be seen that the number of coarse second phase particles in the plate is very small, and it is fully broken after thermal deformation.

[0058] Figure 5 This is a TEM photo of the hot-rolled plate after aging treatment. It can be seen that disc-shaped strengthening phases are precipitated in the plate, with an average length of 7.1nm and an average thickness of 2.1nm. These fine and dispersed strengthening phases have a good strengthening effect and significantly improve the strength of the alloy.

[0059] Figure 6 The engineering stress-strain curves of the hot-rolled plate stretched along the 0°, 45° and 90° directions after aging treatment. It can be seen that the tensile strength of the plate in these three directions is >600MPa and the elongation is >10%.

[0060] Table 1 below shows the yield strength and tensile strength of the plate of Example 1 along the 0°, 45° and 90° directions, as well as the yield strength and tensile strength of the plate of Example 1 according to the formula IPA = (2× max -X mid -X min ) / 2X max ×100%Where X max , X min , X mid They are the maximum, minimum and middle values ​​of the mechanical performance indicators (yield strength, tensile strength and elongation) in the three directions. It can be seen that the IPA values ​​of the yield strength, tensile strength and elongation of the plate are all less than 5%.

[0061] Table 1. Yield strength, tensile strength, elongation and IPA value of the plate

[0062] Stretch direction 0° 45° 90° IPA Yield strength / MPa 560 539 547 3.0 Tensile strength / MPa 637 605 612 4.5 Elongation / % 10.8 10.2 10.5 4.2

[0063] Combination Figure 1-5 As can be seen from Table 1, the preparation method of the present invention can effectively prepare high-strength, low-anisotropy plates with tensile strength>600MPa, elongation>10%, and IPA<5%. The grains in the plates are equiaxed recrystallized grains with an average size of <50μm, the number of coarse second phases is small, and they are fully broken, so that the plates have lower anisotropy.

[0064] Example 2

[0065] This embodiment prepares a spray-formed 7055 aluminum alloy high-strength and low-anisotropy plate. The difference between this embodiment and embodiment 1 is that the temperature is kept at 450° C. for 6 hours before extrusion in S4, and the other conditions are the same.

[0066] Table 2 below shows the yield strength and tensile strength of the plate of Example 2 along the 0°, 45° and 90° directions, as well as the yield strength and tensile strength of the plate of Example 2 according to the formula IPA = (2× max -X mid -X min ) / 2X max ×100%Where X max , X min , X mid They are the maximum, minimum and middle values ​​of the mechanical performance indicators (yield strength, tensile strength and elongation) in the three directions. It can be seen that the IPA values ​​of the yield strength, tensile strength and elongation of the plate are all less than 5%.

[0067] Table 2. Yield strength, tensile strength, elongation and IPA value of the plate

[0068] Stretch direction 0° 45° 90° IPA Yield strength / MPa 563 545 550 2.8 Tensile strength / MPa 642 612 618 4.2 Elongation / % 11.0 10.6 10.5 4.1

[0069] It can be seen from Table 2 that the preparation method of the present invention can effectively prepare high-strength, low-anisotropy plates with a tensile strength of >600 MPa, an elongation of >10%, and IPA <5%. After being kept warm at 450°C / 6h before hot rolling, the effect is not much different from that of being kept warm at 430°C / 6h, indicating that the insulation effect is good in this temperature range.

[0070] Example 3

[0071] This embodiment prepares a spray-formed 7055 aluminum alloy high-strength and low-anisotropy plate. The difference between this embodiment and embodiment 1 is that the solid solution system in step S4 is 450°C / 1h+475°C / 2h, and the other conditions are the same.

[0072] Table 3 below shows the yield strength and tensile strength of the plate of Example 3 along the 0°, 45° and 90° directions, as well as the yield strength and tensile strength of the plate of Example 3 according to the formula IPA = (2× max -X mid -X min ) / 2X max ×100%Where X max , X min , X mid They are the maximum, minimum and middle values ​​of the mechanical performance indicators (yield strength, tensile strength and elongation) in the three directions. It can be seen that the IPA values ​​of the yield strength, tensile strength and elongation of the plate are all less than 5%.

[0073] Table 3. Yield strength, tensile strength, elongation and IPA value of the plate

[0074] Stretch direction 0° 45° 90° IPA Yield strength / MPa 571 550 556 3.2 Tensile strength / MPa 646 615 626 3.9 Elongation / % 11.2 10.7 10.6 4.9

[0075] As can be seen from Table 3, the preparation method of the present invention can effectively prepare high-strength, low-anisotropy plates with tensile strength>600MPa, elongation>10%, and IPA<5%. Extending the second-stage 475°C insulation time to 2h before hot rolling is beneficial to further dissolution of the coarse second phase, and increases the number of solute atoms, thereby improving the elongation and strength of the plate.

[0076] Example 4

[0077] This embodiment prepares a spray-formed 7055 aluminum alloy high-strength and low-anisotropy plate. The difference between this embodiment and embodiment 1 is that the aging system in step S4 is 110° C. / 24 h, and the other conditions are the same.

[0078] Table 4 below shows the yield strength and tensile strength of the plate of Example 4 along the 0°, 45° and 90° directions, as well as the yield strength and tensile strength of the plate of Example 4 according to the formula IPA = (2× max -X mid -X min ) / 2X max×100%Where X max , X min , X mid They are the maximum, minimum and middle values ​​of the mechanical performance indicators (yield strength, tensile strength and elongation) in the three directions. It can be seen that the IPA values ​​of the yield strength, tensile strength and elongation of the plate are all less than 5%.

[0079] Table 4. Yield strength, tensile strength, elongation and IPA value of the plate

[0080] Stretch direction 0° 45° 90° IPA Yield strength / MPa 550 531 542 2.5 Tensile strength / MPa 625 602 605 3.4 Elongation / % 11.0 10.5 10.9 2.7

[0081] It can be seen from Table 4 that the preparation method of the present invention can effectively prepare high-strength, low-anisotropy plates with tensile strength>600MPa, elongation>10%, and IPA<5%, but due to its low aging temperature, the precipitation and growth of the strengthening phase are insufficient, so the strength is slightly lower than that of other embodiments.

[0082] Comparative Example 1

[0083] The main difference between this comparative example and Example 1 is that a homogenization heat treatment of 450°C / 8h+470°C / 24h is performed before hot rolling, and the anisotropy of the alloy is more obvious. The specific implementation steps are as follows:

[0084] S1. A 7055 aluminum alloy ingot with an average grain size of 45.8 μm and a second phase area fraction of 6.2% prepared by a spray forming method.

[0085] S2. Cut ingots with a size of 200mm*150mm*10mm, and perform homogenization heat treatment at 450℃ / 6h+470℃ / 24h before hot rolling to form Al3Zr particles in the ingot.

[0086] S3. The ingot after homogenization heat treatment is hot rolled, the initial rolling temperature is 450°C, the plate is rolled from 10 mm to 2 mm in 8 passes, the deformation amount of each rolling is 10-20%, the temperature after rolling is 420°C, and the hot rolled plate is water-cooled.

[0087] S4. Use an air heating furnace to perform solution heat treatment on the hot-rolled plate at 450℃ / 1h+473℃ / 1h, then use room temperature water quenching, the quenching transfer time is 10s, and after quenching, put the plate into an oil bath furnace at 120℃ for aging treatment within 1min, the aging time is 22h.

[0088] Table 5 below shows the yield strength and tensile strength of the plate in Comparative Example 1 along the 0°, 45° and 90° directions, as well as the yield strength and tensile strength of the plate according to the formula IPA = (2× max -X mid -X min) / 2X max ×100%Where X max , X min , X mid They are the maximum, minimum and middle values ​​of the mechanical performance indicators (yield strength, tensile strength and elongation) in the three corresponding directions. It can be seen that the IPA values ​​of the yield strength and tensile strength of the plate are greater than 8%, and the IPA value of the elongation is greater than 28%, and the anisotropy is significantly increased; and the tensile strength of the sample loaded along 45° is less than 600MPa; the elongation of the sample loaded along 45° and 90° is less than 10%.

[0089] Table 5. Yield strength, tensile strength, elongation and IPA value of the plate

[0090]

[0091]

[0092] Figure 7 This is a TEM photo of the hot-rolled plate after homogenization heat treatment. It can be seen that Al3Zr particles with a size of 20-40nm are precipitated in the plate. During the subsequent hot rolling and solution heat treatment process, these particles will pin dislocations and hinder dislocation movement, thereby inhibiting recrystallization and improving the anisotropy of the plate.

[0093] Figure 8 This is a metallographic photograph of the hot-rolled plate after solution treatment. It can be seen that the grain structure of the plate is an incompletely recrystallized grain. Some of the unrecrystallized structures are strip-shaped squares along the rolling direction, which improves the anisotropy of the plate.

[0094] Comparative Example 2

[0095] The main difference between this comparative example and Example 1 is that a double-stage aging treatment of 120°C / 24h+177°C / 8h is performed after solution treatment and quenching. The alloy plate also has good anisotropy, but the strength is significantly reduced. The specific implementation steps are as follows:

[0096] S1, 7055 aluminum alloy ingot with an average grain size of 45.8 μm and a second phase area fraction of 6.2% prepared by spray forming.

[0097] S2, cut the ingot into the size of 200mm*150mm*10mm, and heat treat it at 430℃ for 4h before extrusion to reduce the residual phase particles in the ingot.

[0098] S3, hot rolling the ingot after homogenization heat treatment, the initial rolling temperature is 450℃, the plate is rolled from 10mm thickness to 2mm thickness through 8 passes, the deformation amount of each rolling is 10-20%, the temperature after rolling is 420℃, and the hot rolled plate is water-cooled.

[0099] S4, using an air heating furnace, the hot-rolled plate is subjected to a 450℃ / 1h+473℃ / 1h solid solution heat treatment, and then quenched in room temperature water with a quenching transfer time of 10s. After quenching, the plate is placed in an oil bath furnace at a temperature of 120℃ for aging treatment within 1min, and the aging time is 24h. The plate is then placed in an oil bath furnace at 177℃ for a second-level aging treatment, and the second-level aging time is 8h.

[0100] Table 6 below shows the yield strength and tensile strength of the plate in Comparative Example 2 along the 0°, 45° and 90° directions, as well as the yield strength and tensile strength of the plate according to the formula IPA = (2× max -X mid -X min ) / 2X max ×100%Where X max , X min , X mid They are the maximum, minimum and middle values ​​of the mechanical performance indicators (yield strength, tensile strength and elongation) in the three directions. It can be seen that the IPA values ​​of the yield strength, tensile strength and elongation of the plate are all less than 6%, but the strength of the plate is significantly reduced, and the tensile strength in each direction is less than 600MPa.

[0101] Table 6. Yield strength, tensile strength, elongation and IPA value of the plate

[0102] Stretch direction 0° 45° 90° IPA Yield strength / MPa 529 518 505 3.3 Tensile strength / MPa 586 567 560 3.8 Elongation / % 14.5 13.8 13.5 5.9

[0103] Fig. 9 This is a metallographic photograph of the hot-rolled plate after solution heat treatment. It can be seen that the grains in the plate are equiaxed recrystallized grains with an average grain size of 39.2μm, which is similar to Figure 3 The metallographic structure of Example 1 is similar, which shows that such equiaxed recrystallized grains are beneficial to reducing anisotropy.

[0104] Fig.10 This is a TEM photo of the hot-rolled plate after double-stage aging treatment. It can be seen that the average length of the strengthening phase particles in the plate is 12.9nm and the average width is 3.5nm. Figure 8 It can be seen that after double-stage aging, the strengthening phase in the plate coarsened and the number density decreased, resulting in a significant decrease in the alloy strength.

[0105] Comparative Example 3

[0106] The main difference between this comparative example and Example 1 is that no 430°C insulation treatment is performed before hot rolling, and the plate cracks during the rolling process. The specific implementation steps are as follows:

[0107] S1. A 7055 aluminum alloy ingot with an average grain size of 45.8 μm and a second phase area fraction of 6.2% prepared by a spray forming method.

[0108] S2. Cut ingots with a size of 200mm*150mm*10mm, heat them to the initial rolling temperature and start rolling directly. When the rolling deformation is 50%, the plate cracks and through cracks are generated in the vertical rolling direction, making it impossible to prepare the plate.

[0109] Comparative Example 3 shows that it is necessary to keep the ingot at 430°C / 6h before rolling in Example 1. This treatment can reduce the amount of residual phase and improve the thermal deformation ability of the alloy.

[0110] In combination with Example 1 and Comparative Examples 1, 2 and 3, it can be seen that the present method can effectively prepare injection-formed 7055 aluminum alloy sheets with high strength and anisotropy, and does not require homogenization heat treatment and two-stage aging heat treatment in the traditional preparation process, which can effectively shorten the process flow and reduce production costs.

[0111] Comparative Example 4

[0112] The main difference between this comparative example and Example 1 is that the 7055 aluminum alloy ingot is not prepared by the injection molding process, but is prepared by conventional crystallizer casting, the ingot grain size is ≥100 μm, the second phase area fraction is ≥10%, and the other specific implementation steps are the same as those in Example 1:

[0113] Table 7 below shows the yield strength and tensile strength of the plate in Comparative Example 4 along the 0°, 45° and 90° directions, as well as the yield strength and tensile strength of the plate according to the formula IPA = (2× max -X mid -X min ) / 2X max ×100%Where X max , X min , X mid They are the maximum, minimum and middle values ​​of the values ​​in the three directions corresponding to the mechanical properties (yield strength, tensile strength and elongation).

[0114] Table 7. Yield strength, tensile strength, elongation and IPA value of the plate

[0115] Stretch direction 0° 45° 90° IPA Yield strength / MPa 550 523 530 4.3 Tensile strength / MPa 623 576 589 6.5 Elongation / % 10.2 7.5 8.4 22.1

[0116] The ingots prepared by the smelting and casting method have a large area fraction of the second phase and more Fe-rich phases, which are difficult to eliminate without long-term homogenization. Therefore, they are retained during subsequent processing and distributed along the processing direction, causing the plate to be more prone to fracture when loaded at 45° and 90°, so the elongation is less than 10%; it is difficult to achieve the effect of the present invention by traditional smelting and casting alloys without homogenization.

[0117] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A preparation process of 7055 sheet material, characterized in that: The following steps are involved: S1. Preheating the 7055 aluminum alloy ingot prepared by the spray forming process; S2. The preheated aluminum alloy ingot is hot rolled, cooled, solutionized, and quenched; The grain size of the 7055 aluminum alloy ingot prepared by the spray forming process is less than 100 μm, and the area fraction of the second phase is less than 10%.

2. The preparation process of the 7055 sheet material according to claim 1, characterized in that: In step S1, the preheating step is to keep the temperature at 400-450°C for 2-8 hours.

3. The preparation process of the 7055 sheet material according to claim 1, characterized in that: In step S2, the hot rolling temperature is 420-450°C.

4. The preparation process of the 7055 sheet material according to claim 1, characterized in that: In step S2, the temperature of the rolled plate after hot rolling is not less than 420°C.

5. The preparation process of the 7055 sheet material according to claim 1, characterized in that: In step S2, the hot rolling is performed for 7 to 9 passes.

6. The preparation process of the 7055 sheet material according to claim 5, characterized in that: In step S2, the deformation amount of a single pass is 10-15%; and / or the total deformation amount of the hot rolling is 80-90%.

7. The preparation process of 7055 sheet material according to claim 1, characterized in that: In step S2, the solution temperature is 450-490°C, and the solution time is 1-6 hours.

8. The preparation process of 7055 sheet material according to claim 1, characterized in that: In step S2, the quenching method includes water-cooling quenching.

9. The preparation process of 7055 sheet material according to claim 1, characterized in that: In step S2, aging treatment is further included after quenching; and / or the temperature of the aging treatment is 100-130° C., and the time of the aging treatment is 16-28 hours.

10. Use of the preparation process of the 7055 plate according to any one of claims 1 to 9 in the preparation of aerospace components or automobile components.

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