A non-isothermal aging process for 7xxx aluminum alloys near curvatures

Abstract

The present application relates to the technical field of aluminum alloy heat treatment, and discloses a non-isothermal aging process for 7xxx aluminum alloy near curvature variable speed, which comprises solid solution quenching, first-stage temperature rising aging, second-stage temperature rising aging, isothermal short-time holding treatment, first-stage temperature falling aging, second-stage temperature falling aging and quenching treatment. The first-stage and second-stage temperature rising aging can make the alloy internal precipitated phase nucleate and grow, and the suitable holding time can ensure the basic performance of the metastable phase. After the aluminum alloy is treated by the improved non-isothermal aging process, the intracrystalline precipitated phase of the aluminum alloy is small and uniformly distributed, the grain boundary precipitated phase is discontinuously chain-shaped distributed, and the comprehensive performance of the aluminum alloy is reasonably controlled. The present application makes the aluminum alloy have excellent mechanical properties and corrosion resistance in a short aging process, improves the application possibility of the aluminum alloy, saves labor and machine costs, and provides a powerful choice for actual industrial production.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy heat treatment technology, specifically to a non-isothermal aging process for 7xxx aluminum alloy with near-curvature variable speed. Background Technology

[0002] 7xxx aluminum alloys, as heat-treatable wrought aluminum alloys, are widely used in aerospace and automotive parts manufacturing due to their advantages such as low density, high specific strength, excellent weldability, and good machinability. In recent years, to enable 7xxx aluminum alloys to possess both good mechanical properties and corrosion resistance, researchers have developed various aging processes, but these all have limitations in practical applications. Single-stage aging provides high strength but poor corrosion resistance, while double-stage aging requires sacrificing strength to achieve good corrosion resistance. Regression aging, although combining both, has a long processing time and strict requirements on the workpiece, significantly reducing actual production efficiency. Therefore, based on existing traditional aging technologies, it is of great significance to develop a heat treatment process that can simultaneously optimize the mechanical properties and corrosion resistance of 7xxx aluminum alloys while shortening the aging time.

[0003] To address the aforementioned issues, we propose a non-isothermal aging process for 7xxx aluminum alloys with near-curvature speed variation. Summary of the Invention

[0004] The purpose of this invention is to provide a non-isothermal aging process for near-curvature speed-changing 7xxx aluminum alloys to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a non-isothermal aging process for near-curvature variable speed aluminum alloys, comprising the following steps:

[0006] The first step is solution treatment; the alloy is placed in a temperature range of 460℃~480℃ for a period of time to form a large amount of supersaturated solid solution in the aluminum alloy matrix;

[0007] The second step is quenching treatment; the solution-treated aluminum alloy is quickly transferred for room temperature water quenching, so that the precipitated phase is fully integrated into the supersaturated solid solution;

[0008] The third step is the first-stage heating and aging treatment; the aluminum alloy is placed in an initial temperature of T. A In a constant temperature forced-air drying oven, at a rate V A From the initial temperature T A Heat to temperature T B ;

[0009] Step 4: Secondary heating and aging treatment; the constant temperature drying oven reaches temperature T. B Afterwards, the temperature inside the constant temperature drying oven increases at a rate V. B From temperature TB temperature T C ;

[0010] fifth step, the aluminum alloy is kept at temperature T C for t hours;

[0011] sixth step, primary temperature decreasing aging treatment; the aluminum alloy kept at temperature T C for t hours is decreased to temperature T B at rate V C ; B ;

[0012] seventh step, secondary temperature decreasing aging treatment; after the temperature inside the constant temperature blast drying oven is decreased to temperature T B , the aluminum alloy is continuously decreased to temperature T A at rate V B ; A ;

[0013] eighth step, quenching treatment; the aluminum alloy is transferred to a fluid to cool rapidly to room temperature, ensuring the aluminum alloy is in a state of out of furnace.

[0014] Preferably, the transfer time of the second step quenching treatment and the transfer time of the eighth step quenching treatment are both not more than 10s.

[0015] Preferably, the fluid of the second step quenching treatment and the fluid of the eighth step quenching treatment are both water or polymer organic quenching liquid.

[0016] Preferably, temperature T B in the third step primary temperature increasing aging treatment and temperature T B in the sixth step primary temperature decreasing aging treatment are both more than twice of temperature T A .

[0017] Preferably, the initial temperature T A is in the range of 20℃~40℃, and temperature T B is in the range of 95℃~105℃.

[0018] Preferably, temperature T C in the fourth step secondary temperature increasing aging treatment and temperature T C in the sixth step primary temperature decreasing aging treatment are both not more than twice of temperature T B .

[0019] Preferably, temperature T C is not more than 180℃, and t hours is in the range of 0.5h~1.5h.

[0020] Preferably, rate V A is in the range of 40℃ / h~60℃ / h, and rate VB In the range of 20℃ / h~30℃ / h.

[0021] Compared with the prior art, the present application has the beneficial effects of:

[0022] 1. The present application can reasonably regulate the behavior change of the precipitated phase in the aluminum alloy, wherein the intracrystalline precipitated phase is in large quantity and fine and dispersed, the grain boundary precipitated phase is independent and round, and is discontinuously distributed in chain shape. The cooperation of the two can make the aluminum alloy obtain high mechanical properties and high corrosion resistance at the same time.

[0023] 2. The present application can shorten the aging time, reduce the labor and machine costs, and improve the production efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 A 7xxx aluminum alloy near-curvature variable-speed non-isothermal aging process and a complete curvature process diagram are provided for the present application.

[0025] Figure 2 A columnar graph of the performance parameter values of the aluminum alloy obtained in embodiments 1-6 in the 7xxx aluminum alloy near-curvature variable-speed non-isothermal aging process provided for the present application is provided.

[0026] Figure 3 Basic parameters of the electrochemical corrosion of the aluminum alloy obtained in embodiments 1-6 in the 7xxx aluminum alloy near-curvature variable-speed non-isothermal aging process provided for the present application are provided.

[0027] Figure 4 A bright-field transmission electron microscope image of the aluminum alloy obtained in embodiment 6 in the 7xxx aluminum alloy near-curvature variable-speed non-isothermal aging process provided for the present application is provided. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings of the embodiments of the present application. Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 It should be apparent that the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0029] It should be noted that, first, the 7xxx aluminum alloy near-curvature variable-speed non-isothermal aging process provided by the present application is suitable for 7xxx aluminum alloys.

[0030] Secondly, GP zone is a kind of quasi-stable phase fine out-solution precipitate precipitated by homogeneous nucleation during out-solution of solid solution, and its crystal structure is basically the same as that of main crystal, and the two are coherent with each other;Chemical composition is between main crystal and balanced stable out-solution phase and is closer to the composition of main crystal;It is small in shape and is small in thickness (or diameter), and can only have one or several unit cell widths, and is distributed in groups and parallel to each other in the main crystal. Because their nucleation energy is much smaller than that of the balanced stable out-solution phase, they are often formed first before the stable phase is formed. Or, under the condition that the ion diffusion in the solid solution is inhibited at a lower temperature. GP zone is often seen in alloys that are quenched and then annealed, and is mainly found in pyroxene and amphibole minerals. The formation of GP zone is a homogeneous nucleation process, and the coherent relationship between the new phase and the parent phase will disappear during the process. Spinodal decomposition is a nucleation-free transformation process, in which a solid solution is decomposed into two solid solutions with the same structure and different compositions. In the spinodal decomposition process, solute atoms diffuse from low-concentration areas to high-concentration areas, and the parent phase and the new phase always maintain coherent relationship.

[0031] In addition, the η phase is a kind of intermetallic compound phase based on Ni3Ti composition, which is a close-packed hexagonal ordered phase. Its composition is fixed and not easy to solid solution with other elements. There are two kinds of shapes: grain boundary cell shape and intracrystalline sheet shape or widmanstatten shape. The strength of the alloy with η phase decreases.

[0032] 7XXX series aluminum alloy after non-isothermal aging, intracrystalline precipitated phase is mainly metastable η' phase, and is semi-coherent with matrix, so the precipitation and growth of η' phase is the main reason to improve the mechanical properties of the alloy. Secondly, the corrosion generally occurs along the grain boundary, and the continuous corrosion process of grain boundary precipitated phase is poor in corrosion resistance, and the discontinuous distribution will hinder the corrosion and improve the corrosion resistance. Grain boundary precipitated phase is mainly η phase, so the distribution of grain boundary precipitated phase is usually used as a standard to judge the good and bad of corrosion resistance.

[0033] Finally, the precipitation sequence of 7XXX series aluminum alloy is GP zone→η' phase→η phase.

[0034] Reference Figure 1 The 7xxx aluminum alloy non-isothermal aging process of the present application is provided, and the technical scheme is as follows:

[0035] The first step is solid solution treatment. The alloy is placed in the temperature range of 460 DEG C to 480 DEG C for a period of time, so that a large number of supersaturated solid solution is formed in the aluminum alloy matrix;

[0036] The second step is quenching treatment. The quenched aluminum alloy is quickly transferred to room temperature water quenching, so that the precipitated phase is fully dissolved into the supersaturated solid solution.

[0037] The third step is a first-stage temperature rising aging treatment; the aluminum alloy is placed in a constant-temperature blast drying oven with an initial temperature of T A , and is heated from the initial temperature T A to the temperature T B at a rate V A .

[0038] The fourth step is a second-stage temperature rising aging treatment; after the temperature T B is reached in the constant-temperature blast drying oven, the temperature in the constant-temperature blast drying oven is raised from the temperature T B to the temperature T C at a rate V B .

[0039] The fifth step is to place the aluminum alloy at the temperature T C for t hours.

[0040] The sixth step is a first-stage temperature falling aging treatment; the aluminum alloy placed at the temperature T C for t hours is cooled from the temperature T C to the temperature T B at a rate V B .

[0041] The seventh step is a second-stage temperature falling aging treatment; after the temperature T B is reached in the constant-temperature blast drying oven, the aluminum alloy is continuously cooled from the temperature T B to the temperature T A at a rate V A .

[0042] The eighth step is a quenching treatment; the aluminum alloy is transferred to a fluid to be rapidly cooled to room temperature, so as to ensure that the aluminum alloy is in a furnace-out state.

[0043] Figure 1 The thick solid line in the figure represents the specific process of the present application, and the thin solid line represents a non-isothermal aging process with an approximate curvature. The non-isothermal aging process with a near-curvature variable speed for the 7xxx aluminum alloy proposed by the present application has been maximized to approach a complete curvature.

[0044] Further, the transfer time of the second quenching treatment and the transfer time of the eighth quenching treatment should not exceed 10s.

[0045] Further, the fluid of the second quenching treatment and the fluid of the eighth quenching treatment are both water or a polymer organic quenching liquid.

[0046] Further, the temperature T B in the third step and the temperature T B in the sixth step are both greater than twice the temperature T A .

[0047] Further, the initial temperature T A In the range of 20℃~40℃, the temperature T B In the range of 95℃~105℃.

[0048] Further, the temperature T C In the fourth step of the secondary temperature rising aging treatment, and the temperature T C In the sixth step of the primary temperature falling aging treatment, shall not exceed twice of the temperature T B .

[0049] Further, the temperature T C Does not exceed 180℃, and t hours is in the range of 0.5h~1.5h.

[0050] Further, the rate V A Is in the range of 40℃ / h~60℃ / h, and the rate V B Is in the range of 20℃ / h~30℃ / h.

[0051] The application is described by specific examples:

[0052] The mass components of the aluminum alloy in the examples 1-6 are: Zn-5.91%, Mg-2.40%, Cu-1.5%, Cr-0.18%, Mn-0.03%, Fe-0.17%, Si-0.09%, and the balance is Al.

[0053] Example 1

[0054] In the first step of the solid solution treatment, the aluminum alloy is put into a box-type resistance furnace at 470℃ for 2h;

[0055] In the second step of the quenching treatment, the aluminum alloy after the solid solution treatment is quenched in water at room temperature, and the quenching transfer time is not more than 5s;

[0056] In the third step of the primary temperature rising aging treatment, the aluminum alloy is put into a constant temperature blast drying oven with an initial temperature of 25℃, and is raised to 100℃ at a rate of 60℃ / h;

[0057] In the fourth step of the secondary temperature rising aging treatment, the aluminum alloy is continuously raised from 100℃ to 150℃ at a rate of 20℃ / h;

[0058] In the fifth step, the aluminum alloy is kept in a constant temperature blast drying oven at 150℃ for 0.5h;

[0059] In the sixth step of the primary temperature falling aging treatment, the aluminum alloy is raised from 150℃ to 100℃ at a rate of 20℃ / h;

[0060] In the seventh step of the secondary temperature falling aging treatment, the aluminum alloy is lowered from 100℃ to 25℃ at a rate of 60℃ / h.

[0061] The eighth step is quenching, in which the aluminum alloy is transferred within 5 seconds and air-cooled.

[0062] The aluminum alloy has a surface hardness of 182.4 HV, a tensile strength of 577 MPa, and an elongation of 11.4%. Figure 2 As shown, the self-corrosion current density of the alloy is 2.11 × 10⁻⁶. -3 mA / cm -2 The corrosion rate is 0.066 mm / a.

[0063] Example 2

[0064] The first step is solution treatment, in which the aluminum alloy is placed in a box-type resistance furnace and held at 470℃ for 2 hours;

[0065] The second step is quenching. After solution treatment, the aluminum alloy is quenched at room temperature, and the quenching transfer time does not exceed 5 seconds.

[0066] The third step is the first-stage temperature rise aging treatment, in which the aluminum alloy is placed in a constant temperature forced-air drying oven with an initial temperature of 40℃ and heated to 100℃ at a rate of 60℃ / h.

[0067] The fourth step is a secondary heating and aging treatment, in which the aluminum alloy is heated from 100℃ to 150℃ at a rate of 20℃ / h.

[0068] The fifth step is to keep the aluminum alloy at a constant temperature of 150℃ in a forced-air drying oven for 0.5 hours;

[0069] The sixth step is a first-stage cooling and aging treatment, in which the aluminum alloy is cooled from 150°C to 100°C at a rate of 20°C / h.

[0070] The seventh step is a secondary cooling and aging treatment, in which the aluminum alloy is cooled from 100°C to 40°C at a rate of 60°C / h.

[0071] The eighth step is quenching, in which the aluminum alloy is transferred within 5 seconds and air-cooled to room temperature.

[0072] The alloy has a surface hardness of 184.6 HV, a tensile strength of 589 MPa, and an elongation of 11.2%. Figure 2 As shown, the self-corrosion current density of the alloy is 1.96 × 10⁻⁶. -3 mA / cm -2 The corrosion rate is 0.064 mm / a.

[0073] The GP region can precipitate at relatively low temperatures and is completely coherent with the matrix. A comparison of Examples 1 and 2 shows that increasing the initial temperature T within the range of 20°C to 40°C... A, the number of GP zones formed is relatively small when the second-stage temperature decreasing aging treatment in the seventh step of Example 2 is performed in this range, the "softening" effect on the aluminum alloy is slightly reduced, the strength and hardness are slightly increased, but the corrosion resistance does not change significantly.

[0074] Example 3

[0075] The first step of solution treatment is to place the aluminum alloy in a box-type resistance furnace at 470℃ for 2h;

[0076] The second step of quenching treatment is to quench the alloy at room temperature after solution treatment, and the quenching transfer time is not more than 5s;

[0077] The third step of first-stage temperature increasing aging treatment is to place the aluminum alloy in a constant temperature air drying oven with an initial temperature of 40℃, and increase the temperature to 100℃ at a rate of 40℃ / h;

[0078] The fourth step of second-stage temperature increasing aging treatment is to continue to increase the temperature of the aluminum alloy from 100℃ to 150℃ at a rate of 20℃ / h;

[0079] The fifth step is to keep the aluminum alloy in a constant temperature air drying oven at 150℃ for 0.5h;

[0080] The sixth step of first-stage temperature decreasing aging treatment is to decrease the temperature of the aluminum alloy from 150℃ to 100℃ at a rate of 20℃ / h;

[0081] The seventh step of second-stage temperature decreasing aging treatment is to decrease the temperature of the aluminum alloy from 100℃ to 40℃ at a rate of 40℃ / h.

[0082] The eighth step of quenching treatment is to transfer the aluminum alloy within 5s and perform air cooling treatment to cool it to room temperature.

[0083] The surface hardness of the aluminum alloy is 198.5HV, the tensile strength is 630MPa, and the elongation is 9.5%. As shown in Figure 2 , the self-corrosion current density of the alloy is 0.76×10 -3 mA / cm -2 , and the corrosion rate is 0.025mm / a.

[0084] The aluminum alloy is subjected to first-stage temperature increasing aging at a temperature increasing rate of 20℃ / h~40℃ / h to charge and precipitate GP zones in the matrix, and to ensure the conversion rate of metastable phase, thereby preparing for the following second-stage temperature increasing aging.

[0085] As can be seen from the comparison between Example 2 and Example 3, reducing the first-stage temperature increasing rate V AThis may lead to more complete nucleation and growth of the intragranular precipitates in Example 3, a slightly slower secondary precipitation process, and a stronger nucleation ability. The grain boundary precipitates are discontinuously distributed, improving the mechanical properties and corrosion resistance of the alloy.

[0086] Example 4

[0087] The first step is solution treatment, in which the aluminum alloy is placed in a box-type resistance furnace and held at 470℃ for 2 hours;

[0088] The second step is quenching. After solution treatment, the aluminum alloy is quenched at room temperature, and the quenching transfer time does not exceed 5 seconds.

[0089] The third step is the first-stage heating and aging treatment, in which the aluminum alloy is placed in a constant temperature drying oven with an initial temperature of 40℃ and heated to 100℃ at a rate of 40℃ / h.

[0090] The fourth step is a secondary heating and aging treatment, in which the aluminum alloy is heated from 100°C to 175°C at a rate of 20°C / h.

[0091] The fifth step is to keep the aluminum alloy at a constant temperature of 170℃ in a forced-air drying oven for 0.5 hours;

[0092] The sixth step is a first-stage cooling and aging treatment, in which the aluminum alloy is cooled from 175°C to 100°C at a rate of 20°C / h.

[0093] The seventh step is a secondary cooling and aging treatment, in which the aluminum alloy is cooled from 100°C to 40°C at a rate of 40°C / h.

[0094] The eighth step is quenching, in which the aluminum alloy is transferred within 5 seconds and air-cooled to room temperature.

[0095] The aluminum alloy has a surface hardness of 189.5 HV, a tensile strength of 604 MPa, and an elongation of 10.7%. Figure 2 As shown, the self-corrosion current density of the alloy is 1.49 × 10⁻⁶. -3 mA / cm -2 The corrosion rate is 0.048 mm / a.

[0096] Temperature T C The temperature should not exceed T. B This doubles the amount of η' phase, resulting in less transformation and coarsening of the η' phase, laying a good foundation for the secondary precipitation process during the cooling stage, and better controlling the changes in the precipitated phase of the alloy.

[0097] Comparing Examples 3 and 4, it can be seen that increasing the maximum temperature T C This may cause the η' phase in Example 4 to fully transform and coarsen, making the effect of the coarsening phase more pronounced. This results in poor performance of the secondary precipitates, leading to a decrease in the mechanical properties of the alloy. Grain boundary precipitation also causes coarsening, resulting in a slight decrease in corrosion resistance.

[0098] Example 5

[0099] The first step is solution treatment, in which the aluminum alloy is placed in a box-type resistance furnace and held at 470℃ for 2 hours;

[0100] The second step is quenching. After solution treatment, the aluminum alloy is quenched at room temperature, and the quenching transfer time does not exceed 5 seconds.

[0101] The third step is the first-stage heating and aging treatment, in which the aluminum alloy is placed in a constant temperature drying oven with an initial temperature of 40℃ and heated to 100℃ at a rate of 40℃ / h.

[0102] The fourth step is a secondary heating and aging treatment, in which the aluminum alloy is heated from 100°C to 150°C at a rate of 30°C / h.

[0103] The fifth step is to keep the aluminum alloy at a constant temperature of 150℃ in a forced-air drying oven for 0.5 hours;

[0104] The sixth step is a first-stage cooling and aging treatment, in which the aluminum alloy is cooled from 150°C to 100°C at a rate of 30°C / h.

[0105] The seventh step is a secondary cooling and aging treatment, in which the aluminum alloy is cooled from 100°C to 40°C at a rate of 40°C / h.

[0106] The eighth step is quenching, in which the aluminum alloy is transferred within 5 seconds and air-cooled to room temperature.

[0107] The alloy has a surface hardness of 190.3 HV, a tensile strength of 611 MPa, and an elongation of 10.6%. Figure 2 As shown, the self-corrosion current density of the alloy is 1.05 × 10⁻⁶. -3 mA / cm -2 The corrosion rate is 0.034 mm / a.

[0108] To ensure that the secondary heating rate is within the range of 20℃ / h to 30℃ / h, firstly, the GP region that was not fully transformed during the primary heating and aging stage is fully transformed at a suitable rate. Secondly, the η' phase is transformed and precipitated again without excessive coarsening. Finally, the secondary precipitated phase is reasonably precipitated and acts on the matrix.

[0109] A comparison of Examples 3 and 5 shows that increasing the aging rate VB of the secondary non-isothermal aging treatment may result in insufficient stable phase nucleation ability in Example 5, a faster secondary precipitation process, and less significant intragranular phase growth, leading to a slight decrease in the hardness and strength of the aluminum alloy. Incomplete segregation of solute atoms at grain boundaries also results in a faster corrosion rate and slightly poorer corrosion resistance.

[0110] Example 6

[0111] The first step is solution treatment, in which the aluminum alloy is placed in a box-type resistance furnace and held at 470℃ for 2 hours;

[0112] The second step is quenching. After solution treatment, the aluminum alloy is quenched at room temperature, and the quenching transfer time does not exceed 5 seconds.

[0113] The third step is the first-stage heating and aging treatment, in which the aluminum alloy is placed in a constant temperature drying oven with an initial temperature of 40℃ and heated to 100℃ at a rate of 40℃ / h.

[0114] The fourth step is a secondary heating and aging treatment, in which the aluminum alloy is heated from 100℃ to 150℃ at a rate of 20℃ / h.

[0115] The fifth step is to keep the aluminum alloy in a constant temperature drying oven at 150℃ for 1 hour;

[0116] The sixth step is a first-stage cooling and aging treatment, in which the aluminum alloy is cooled from 150°C to 100°C at a rate of 20°C / h.

[0117] The seventh step is a secondary cooling and aging treatment, in which the aluminum alloy is cooled from 100°C to 40°C at a rate of 40°C / h.

[0118] The eighth step is quenching, in which the aluminum alloy is transferred within 5 seconds and air-cooled to room temperature.

[0119] The aluminum alloy has a surface hardness of 203.2 HV, a tensile strength of 652 MPa, and an elongation of 9.2%. Figure 2 As shown, the self-corrosion current density of the aluminum alloy is 0.61 × 10⁻⁶. -3 mA / cm -2 The corrosion rate is 0.019 mm / a.

[0120] A comparison of Examples 3 and 6 shows that increasing the holding time t at the highest non-isothermal temperature may cause the intragranular GP region and metastable phase η' in Example 6 to grow sufficiently and undergo transformation, with some GP regions transforming into new fine η' phases. The metastable phase η' generated during the heating and aging stage will transform into fine stable phase η, and will not completely coarsen. Secondary precipitates will not undergo re-dissolution and will be abundant and dense. Therefore, the mechanical properties of the aluminum alloy are further improved. Solute atom segregation at grain boundaries causes grain boundary adsorption, producing PFZ. The grain boundary precipitates are independent, round, and discontinuously distributed, further improving corrosion resistance. It should be noted that PFZ refers to the grain boundary zone without precipitates in materials science and engineering.

[0121] The principle of the non-isothermal aging process of the 7xxx aluminum alloy near curvature variable speed is to further improve the comprehensive performance of the aluminum alloy by using the secondary precipitation in the high temperature aging stage. After the aluminum alloy is solution treated and quenched, the first temperature rising aging treatment is performed, in the temperature range, GP zone and eta prime phase are rapidly generated, with the aging temperature increasing to the second temperature range, the speed is reduced, the nucleation rate of the aluminum alloy is also reduced, and the precipitated phase is reduced. After the alloy is aged for a period of time, the first temperature reduction treatment is performed symmetrically, the precipitated phase is fully grown and the second phase re-dissolution process occurs. During the second temperature reduction aging, the second phase begins to precipitate, new GP zone and eta prime phase are generated again and grow up. After the non-isothermal aging treatment of the near curvature variable speed, the density of the intracrystalline precipitated phase increases, the shape is small and the distribution is uniform, and the grain boundary precipitated phase is discontinuously distributed in chain shape.

[0122] It will be obvious to a person skilled in the art that, without departing from the spirit or essential characteristics of the application, the present application can be implemented in other specific forms. The present examples are therefore to be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the specification as previously given. Thus, any and all variations which do not take away from the novel teachings provided by the application are expressly intended to come within the scope of the present application. Any reference signs in the claims should not be construed as limiting the scope of the claims.

[0123] In addition, it should be understood that, although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be combined appropriately to form other embodiments that those skilled in the art can understand.

Claims

1. A non-isothermal aging process for 7xxx aluminum alloy with near-curvature variable speed, characterized in that, Includes the following steps: The first step is solution treatment; The alloy was placed in a temperature range of 460℃~480℃ for a period of time, which caused a large amount of supersaturated solid solution to form in the aluminum alloy matrix. The second step is quenching treatment; the solution-treated aluminum alloy is quickly transferred for room temperature water quenching, so that the precipitated phase is fully integrated into the supersaturated solid solution; The third step is the first-stage heating and aging treatment; the aluminum alloy is placed in an initial temperature of T. A In a constant temperature forced-air drying oven, at a rate V A From the initial temperature T A Heat to temperature T B ; Step 4: Secondary heating and aging treatment; the constant temperature drying oven reaches temperature T. B Afterwards, the temperature inside the constant temperature drying oven increases at a rate V. B From temperature T B Heat to temperature T C ; The fifth step is to place the aluminum alloy at temperature T. C Maintain for t hours; Step 6: Level 1 cooling and aging treatment; Placed at temperature T C Keep aluminum alloy at rate V for t hours B From temperature T C Cool down to temperature T B ; Step 7: Secondary cooling and aging treatment; The internal temperature of the constant temperature drying oven drops to temperature T. B Then, continue to apply the aluminum alloy at a rate V. A From temperature T B Cool down to temperature T A ; Step 8: Quenching treatment; Transfer the aluminum alloy to a fluid and rapidly cool it to room temperature to ensure the aluminum alloy is in the correct state after exiting the furnace. The initial temperature T A Within the temperature range of 20℃ to 40℃, temperature T B Within the temperature range of 95℃ to 105℃; temperature T C Temperature not exceeding 180℃, time t per hour within the range of 0.5h to 1.5h; rate V A Within the range of 40℃ / h to 60℃ / h, the rate V B Within the range of 20℃ / h to 30℃ / h.

2. The near-curvature variable-speed non-isothermal aging process for 7xxx aluminum alloy according to claim 1, characterized in that, The transfer time of the second quenching process and the transfer time of the eighth quenching process shall not exceed 10 seconds.

3. The non-isothermal aging process for 7xxx aluminum alloy with near-curvature speed variation according to claim 1, characterized in that, The fluid used in the second quenching step and the fluid used in the eighth quenching step are both water or polymer organic quenching fluid.

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