A method for simultaneously improving strength and ductility of aluminum alloys

Abstract

The application provides a method for simultaneously improving strength and plasticity of aluminum alloy, and belongs to the field of aluminum alloy processing.The method comprises the following steps: sequentially performing homogenization treatment and hot extrusion on as-cast aluminum alloy to obtain an extruded rod; sequentially performing solid solution treatment, quenching and double-stage aging treatment on the obtained extruded rod to obtain an aluminum alloy; the double-stage aging treatment comprises sequentially performing first-stage aging and second-stage aging; the holding temperature of the first-stage aging is 110-130 DEG C, and the holding time of the first-stage aging is 60-180 min; the holding temperature of the second-stage aging is 170-200 DEG C, and the holding time of the second-stage aging is 420-480 min.The method can directly use ordinary as-cast aluminum alloy as raw material, and does not need to strictly control alloy components and repeatedly perform heat treatment and plasticity processing, so that the prepared aluminum alloy has high strength and plasticity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum alloy processing, and particularly relates to a method for simultaneously improving strength and plasticity of aluminum alloy. BACKGROUND

[0002] As an important structural material widely used in the field of aerospace, aluminum alloy not only needs to retain the original lightweight characteristics, but also needs to have certain strength and plasticity. However, the strength and plasticity of aluminum alloy are often difficult to improve simultaneously, and the strength and plasticity are in a state of mutual restriction, and the plasticity will decrease when the strength is improved. Therefore, it is difficult for aluminum alloy to simultaneously obtain high strength and plasticity.

[0003] At present, the methods for improving the mechanical properties of aluminum alloy mainly include adjusting alloy composition, plastic deformation and heat treatment. Among them, when adjusting the alloy composition, rare earth and other modifiers are often used, which not only has high cost, but also is difficult to obtain the aluminum alloy with the target component content, and it is difficult to obtain the aluminum alloy meeting the use requirements; the plastic deformation is generally combined with heat treatment, but the steps of plastic deformation and heat treatment are complex, and the parameters are difficult to control, so it is difficult to effectively improve the performance of aluminum alloy. For example, the patent “CN108220699A” discloses a preparation method of high-strength and high-plasticity aluminum alloy double-layer composite plate for vehicle body structural parts. Although the aluminum alloy in the patent has high strength and plasticity, the preparation of the aluminum alloy not only depends on strict control of the composition of the aluminum alloy, but also needs a series of complicated processing steps such as preheating, hot rolling, cold rolling, intermediate annealing, solid solution treatment, quenching and aging treatment, and the process is extremely complex. The patent “CN114318183A” discloses a high-plasticity aluminum alloy part and a preparation method thereof. Although the aluminum alloy prepared by the patent does not need strict control of the composition of the aluminum alloy and complex processing steps, the aluminum alloy to be treated needs to be refined, deslagged and added with rare earth intermediate alloy as a modifier, that is, the initial performance of the aluminum alloy to be treated has high requirements, and the tensile strength of the final prepared aluminum alloy product is less than 300 MPa, and the elongation is less than 10%, and the strength and plasticity of the aluminum alloy are not improved simultaneously.

[0004] Therefore, it is urgent to provide a method which can improve the strength and plasticity of aluminum alloy simultaneously and has simple process. SUMMARY

[0005] The present application aims to provide a method for simultaneously improving the strength and plasticity of aluminum alloy. The method provided by the present application can directly use ordinary as-cast aluminum alloy as raw material, does not need to strictly control the alloy composition and repeatedly perform heat treatment and plastic processing, and can make the prepared aluminum alloy have high strength and plasticity.

[0006] To achieve the above object, the present application provides the following technical solutions.

[0007] The present application provides a method for simultaneously improving the strength and plasticity of an aluminum alloy, comprising the following steps:

[0008] (1) sequentially performing homogenization treatment and hot extrusion on the as-cast aluminum alloy to obtain an extruded rod;

[0009] (2) sequentially performing solid solution treatment, quenching and double-stage aging treatment on the extruded rod obtained in step (1) to obtain an aluminum alloy; the double-stage aging treatment comprises sequentially performing first-stage aging and second-stage aging; the holding temperature of the first-stage aging is 110-130℃, and the holding time of the first-stage aging is 60-180min; the holding temperature of the second-stage aging is 170-200℃, and the holding time of the second-stage aging is 420-480min.

[0010] Preferably, the heating rate from the holding temperature of the first-stage aging to the holding temperature of the second-stage aging in step (2) is 1-3℃ / min.

[0011] Preferably, the holding temperature of the solid solution treatment in step (2) is 490-500℃, and the holding time of the solid solution treatment is 60-70min.

[0012] Preferably, the heating rate from the holding temperature of the first-stage aging to the holding temperature of the second-stage aging in step (2) is 1-3℃ / min.

[0013] Preferably, the quenching process in step (2) comprises: being transferred to a cooling medium of a polyethylene oxide aqueous solution within 10s at the holding temperature of the solid solution treatment and being cooled to room temperature.

[0014] Preferably, the mass concentration of the polyethylene oxide in the polyethylene oxide aqueous solution is 0.1-0.15%, and the relative molecular mass of the polyethylene oxide is 4.5×10 6 -5.5×10 6 .

[0015] Preferably, the holding temperature of the homogenization treatment in step (1) is 483-503℃, and the holding time of the homogenization treatment is 16-18h.

[0016] Preferably, the temperature of the hot extrusion in step (1) is 350-450℃.

[0017] Preferably, the extrusion ratio of the hot extrusion in step (1) is (14-18):1, the extrusion speed of the hot extrusion is 1.5-2.5mm / s, and the direction of the hot extrusion is positive extrusion.

[0018] Preferably, the grade of the as-cast aluminum alloy in step (1) comprises 2024, 2124 or 2219 aluminum alloy.

[0019] The method for simultaneously improving the strength and plasticity of aluminum alloy provided by the present application comprises the following steps: sequentially performing homogenization treatment and hot extrusion on an as-cast aluminum alloy to obtain an extruded rod; sequentially performing solid solution treatment, quenching and double-stage aging treatment on the obtained extruded rod to obtain an aluminum alloy; the double-stage aging treatment comprises sequentially performing first-stage aging and second-stage aging; the holding temperature of the first-stage aging is 110-130℃, and the holding time of the first-stage aging is 60-180min; the holding temperature of the second-stage aging is 170-200℃, and the holding time of the second-stage aging is 420-480min. The as-cast aluminum alloy is first subjected to homogenization treatment in the present application, which can effectively improve the segregation in the as-cast aluminum alloy, making the element distribution more uniform and more conducive to subsequent plastic deformation; the present application combines deformation strengthening and phase transformation strengthening by adopting plastic deformation of hot extrusion and combining with subsequent solid solution treatment and double-stage aging heat treatment process, utilizes the dislocation network introduced by plastic deformation to promote the uniform distribution of precipitated phases, effectively improves the strength and plasticity of the aluminum alloy; and in the first-stage aging of the double-stage aging, the present application generates dense and uniform GP zones at a lower holding temperature, these nanophases can become the nucleation sites of S phases in the aluminum alloy matrix, break the continuous precipitation of the second phase at the grain boundaries of single-stage aging, and at the same time, the S phase size is increased and the distribution is wider under the condition of the second-stage aging at a temperature higher than that of the first-stage aging, so as to simultaneously improve the strength and plasticity of the aluminum alloy, and the aluminum alloy also has good corrosion resistance, which can meet various requirements in the fields of aerospace, industrial manufacturing and the like.

[0020] The results of the embodiments show that the aluminum alloy obtained by the method for simultaneously improving the strength and plasticity of aluminum alloy provided by the present application has a tensile strength of 400-426MPa, a yield strength of 329-342MPa, an elongation of 15.1-16.1%, and a Vickers hardness of 133.7-138.3HV; the aluminum alloy prepared by Comparative Example 1 adopting single-stage aging has a tensile strength of 394MPa, a yield strength of 315MPa, an elongation of 14.7%, and a Vickers hardness of 124.7HV. It can be seen that the method provided by the present application can directly use ordinary as-cast aluminum alloy as raw material, without the need for strict control of alloy composition and repeated heat treatment and plastic processing, so as to make the prepared aluminum alloy have both high strength and plasticity. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 An optical micrograph of the aluminum alloy ingot after homogenization treatment in Example 1 of the present application;

[0022] Figure 2Optical micrograph of the extruded bar after hot extrusion of step (1) of Example 1 of the present application;

[0023] Figure 3 Optical micrograph of the aluminum alloy finally prepared in Example 2 of the present application. DETAILED DESCRIPTION

[0024] The present application provides a method for simultaneously improving the strength and plasticity of an aluminum alloy, comprising the following steps:

[0025] (1) sequentially subjecting an as-cast aluminum alloy to homogenization treatment and hot extrusion to obtain an extruded bar;

[0026] (2) sequentially subjecting the extruded bar obtained in step (1) to solution treatment, quenching and double-stage aging treatment to obtain an aluminum alloy; the double-stage aging treatment comprises sequentially performing first-stage aging and second-stage aging; the holding temperature of the first-stage aging is 110-130℃, and the holding time of the first-stage aging is 60-180min; the holding temperature of the second-stage aging is 170-200℃, and the holding time of the second-stage aging is 420-480min.

[0027] The present application sequentially subjects an as-cast aluminum alloy to homogenization treatment and hot extrusion to obtain an extruded bar.

[0028] In the present application, the grade of the as-cast aluminum alloy is preferably selected from 2024, 2124 or 2219 aluminum alloy. By treating the above-mentioned types of aluminum alloy, the present application can effectively improve the strength and plasticity thereof, and make it better suitable for various requirements in the fields of aerospace, industrial manufacturing and the like.

[0029] In the present application, the holding temperature of the homogenization treatment is preferably 483-503℃, and the holding time of the homogenization treatment is preferably 16-18h. By controlling the holding temperature and holding time of the homogenization treatment within the above-mentioned ranges, the present application can effectively improve the segregation in the as-cast aluminum alloy, and make the element distribution more uniform, which is more conducive to subsequent plastic deformation.

[0030] In the present application, the heating rate for heating to the holding temperature of the homogenization treatment is preferably 8-12℃ / min, and more preferably 10℃ / min. By controlling the heating rate of the homogenization treatment within the above-mentioned range, the present application can uniformly heat the as-cast aluminum alloy, so that it is fully homogenized.

[0031] In the present application, the cooling mode of the homogenization treatment is preferably air cooling to room temperature. By selecting the above-mentioned cooling mode, the present application can be cooled to room temperature more quickly, and reduce the influence of the residual temperature of the homogenization treatment on the alloy structure.

[0032] The product of the homogenization treatment is preferably sequentially subjected to end cutting, face milling and oiling to obtain a homogenized ingot. In the present application, the reagent used for the oiling is preferably graphite oil. The present application does not have special requirements for the specific operation of the end cutting, face milling and oiling, and the conventional operation known in the art can be used. The present application can make the surface of the aluminum alloy more flat and remove the oxide layer through the end cutting and face milling, and can avoid the re-oxidation of the surface of the aluminum alloy caused by the heat treatment through the oiling.

[0033] The present application preferably simultaneously preheats the extrusion die and the homogenized ingot before the hot extrusion. In the present application, the holding temperature of the preheating is preferably the temperature of the hot extrusion, and the holding time of the preheating is preferably 0.5-1.5 h. The present application can make the homogenized ingot and the extrusion die simultaneously at the temperature of the hot extrusion before the hot extrusion through the preheating, thereby reducing the heat loss of the ingot during the hot extrusion.

[0034] In the present application, the temperature of the hot extrusion is preferably 350-450℃. The present application can effectively reduce the resistance to plastic deformation, promote the recrystallization during the hot extrusion, effectively refine the grains, and more favorably improve the strength and plasticity of the aluminum alloy by controlling the temperature of the hot extrusion within the above range.

[0035] In the present application, the extrusion ratio of the hot extrusion is preferably (14-18):1, and more preferably 16:1; the extrusion speed of the hot extrusion is preferably 1.5-2.5 mm / s, and more preferably 2 mm / s; and the direction of the hot extrusion is preferably positive extrusion. The present application can make the aluminum alloy sufficiently deform, effectively close the shrinkage and other casting curves in the as-cast aluminum alloy, and accumulate dislocations and refine grains during the hot extrusion by controlling the extrusion ratio and the extrusion speed of the hot extrusion within the above range.

[0036] The present application preferably cuts the product after the hot extrusion to obtain an extruded bar. The present application does not have special requirements for the specific operation of the cutting, and the conventional operation known in the art can be used. The present application can remove the head and tail portions of the extruded bar to obtain a bar with a proper size through the cutting.

[0037] After obtaining the extruded bar, the present application sequentially subjects the obtained extruded bar to solid solution treatment, quenching and double-stage aging treatment to obtain an aluminum alloy.

[0038] In the present application, the holding temperature of the solid solution treatment is preferably 490-500℃, and the holding time of the solid solution treatment is preferably 60-70 min. The present application can make the second phase particles precipitated in the extruded bar dissolve in the matrix to obtain a solid solution structure, thereby preparing the structure for the subsequent aging of the fine and dispersed phase by controlling the holding temperature and the holding time of the solid solution treatment within the above range.

[0039] In the present application, the heating rate for heating to the holding temperature of the solution treatment is preferably 2-3℃ / min. The present application is more conducive to uniform heating of the hot-extruded rod and ensures that the second-phase particles are fully re-dissolved in the matrix by controlling the heating rate of the solution treatment within the above range.

[0040] In the present application, the quenching process preferably comprises cooling to room temperature in the cooling medium of the polyethylene oxide aqueous solution within 10s at the holding temperature of the solution treatment. The present application can ensure that the aluminum alloy after the solution treatment is rapidly cooled to room temperature by using the above quenching method, so that the second phase in the aluminum alloy does not have time to precipitate, thereby obtaining a saturated solid solution structure.

[0041] In the present application, the mass concentration of polyethylene oxide in the polyethylene oxide aqueous solution is preferably 0.1-0.15%, and more preferably 1%; the relative molecular mass of the polyethylene oxide is preferably 4.5×10 6 -5.5×10 6 , and more preferably 5×10 6 . The present application can ensure that the aluminum alloy after the solution treatment is rapidly cooled to room temperature without cracking by selecting the above cooling medium for quenching treatment.

[0042] In the present application, the two-stage aging comprises sequentially performed first-stage aging and second-stage aging; the holding temperature of the first-stage aging is 110-130℃, and is preferably 120℃; the holding time of the first-stage aging is 60-180min, and is preferably 100-150min. In the present application, the holding temperature of the second-stage aging is 170-200℃, and is preferably 180-190℃; the holding time of the second-stage aging is 420-480min, and is preferably 430-470min. The present application can simultaneously improve the strength and plasticity of the aluminum alloy and also enable the aluminum alloy to have good corrosion resistance by using the heat treatment method of two-stage aging and controlling the parameters of the first-stage aging and the second-stage aging within the above range during the two-stage aging process, i.e., first generating dense and uniform GP zones at a lower holding temperature, which can become the nucleation sites of S phase in the aluminum alloy matrix, and then breaking the continuous precipitation of the second phase at the grain boundaries of the single-stage aging, and subsequently increasing the size of the S phase and making the distribution wider at a temperature higher than that of the first-stage aging.

[0043] In the present application, the heating rate for heating from the holding temperature of the first-stage aging to the holding temperature of the second-stage aging is preferably 1-3℃ / min. The present application can ensure uniform heating of the aluminum alloy by controlling the heating rate from the first-stage aging to the second-stage aging within the above range.

[0044] In the present application, the cooling mode of the second aging is preferably air cooling to room temperature. The present application can reduce the influence of the residual temperature of the second aging on the aluminum alloy structure by selecting the above cooling mode.

[0045] The method provided by the present application can directly use common as-cast aluminum alloy as raw material, does not need to strictly control alloy components and repeatedly perform heat treatment and plastic processing, and can make the prepared aluminum alloy have high strength and plasticity, and the method is simple and the parameters are easy to control.

[0046] The technical solutions in the present application will be clearly and completely described below in combination with the embodiments in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0047] Embodiment 1

[0048] A method for simultaneously improving the strength and plasticity of an aluminum alloy, specifically comprising the following steps:

[0049] (1) sequentially performing homogenization treatment, head cutting, face milling and oiling on as-cast aluminum alloy to obtain a homogenization ingot, then simultaneously preheating an extrusion die and the homogenization ingot to a hot extrusion temperature, then performing hot extrusion and cutting off the head and tail portions to obtain an extruded rod; specifically: the as-cast aluminum alloy is 2024 cast aluminum alloy, the 2024 cast aluminum alloy is placed in a box-type resistance furnace and heated at a heating rate of 10 ℃ / min to 493 ℃ for homogenization treatment for 18 h, and then sequentially subjected to head cutting, face milling and oiling after air cooling to room temperature to obtain a homogenization ingot; the reagent used for oiling is graphite oil; then the extrusion die and the homogenization ingot are placed in a heat treatment furnace for preheating for 1 h to reach a hot extrusion temperature of 410 ℃, and then hot extrusion is performed; the hot extrusion ratio is 16:1, the direction is forward extrusion, and the extrusion speed is 2 mm / s; after the hot extrusion is completed, air cooling is performed to room temperature, and finally the head and tail portions are cut off to obtain a 2024 aluminum alloy extruded rod with a diameter of 15 mm.

[0050] (2) sequentially performing solid solution treatment, quenching and double-stage aging treatment on the extruded rod obtained in the step (1) to obtain an aluminum alloy; specifically: the extruded rod obtained in the step (1) is placed in a heat treatment furnace for 500 ℃ solid solution treatment for 70 min, then transferred to a polyethylene oxide aqueous solution within 10 s to cool to room temperature; then placed in a heat treatment furnace and heated to 110 ℃ for 2 h for first-stage aging; after the first-stage aging is completed, continue to heat at a heating rate of 2 ℃ / min to 170 ℃ for 8 h for second-stage aging, and then air cool to room temperature after the heat preservation is completed to obtain an aluminum alloy.

[0051] Example 2

[0052] The holding temperature of the second aging in step (2) of Example 1 is replaced by 180℃, and the remaining steps are the same as those of Example 1.

[0053] Example 3

[0054] The holding temperature of the second aging in step (2) of Example 1 is replaced by 190℃, and the remaining steps are the same as those of Example 1.

[0055] Comparative Example 1

[0056] The double aging in step (2) of Example 1 is replaced by a single aging, the holding temperature of the single aging is 190℃, and the holding time is 10h, and the remaining steps are the same as those of Example 1.

[0057] The microstructure of the aluminum alloy ingot after the homogenization treatment in step (1) of Example 1 is observed by an optical microscope, and the optical micrograph obtained by the observation is as shown in Figure 1 .

[0058] It can be seen from Figure 1 that the microstructure of the aluminum alloy ingot after the homogenization treatment is relatively uniform, the grain boundary is clear, and the grain size is relatively small, but there is still some segregation in the microstructure.

[0059] The microstructure of the extruded rod after the hot extrusion in step (1) of Example 1 is observed by an optical microscope, and the optical micrograph obtained by the observation is as shown in Figure 2 .

[0060] It can be seen from Figure 2 that the composition segregation in the microstructure of the extruded rod after the hot extrusion is effectively improved, the originally coarse grains are crushed, the grain size is further reduced, and the second phase is more uniformly distributed, which indicates that the extruded rod has high strength and hardness.

[0061] The microstructure of the aluminum alloy prepared in Example 2 is observed by an optical microscope, and the optical micrograph obtained by the observation is as shown in Figure 3 .

[0062] It can be seen from Figure 3 that the grain size is further reduced compared with the extruded rod, and the second phase is more uniformly distributed, and in addition, the second phase particles are obviously reduced, which indicates that the plasticity of the aluminum alloy is improved.

[0063] The mechanical properties of the aluminum alloys prepared in Examples 1-3 and Comparative Example 1 are tested at room temperature according to GB / T228.1-2010 tensile test and GB / T4340.1-2009 Vickers hardness test, and the test results are shown in Table 1.

[0064] Table 1 mechanical property test results of the aluminum alloys of Examples 1-3 and Comparative Example 1

[0065]

[0066] The aluminum alloy prepared by the method for simultaneously improving strength and plasticity of the present application has a tensile strength of 400-426 MPa, a yield strength of 329-342 MPa, an elongation of 15.1-16.1%, and a Vickers hardness of 133.7-138.3 HV. The aluminum alloy prepared by Comparative Example 1 using single-stage aging has a tensile strength of 394 MPa, a yield strength of 315 MPa, an elongation of 14.7%, and a Vickers hardness of 124.7 HV.

[0067] The mechanical properties of the aluminum alloys of Examples 1-3 are significantly better than those of Comparative Example 1.

[0068] In summary, the method of the present application can directly use ordinary as-cast aluminum alloy as raw material, without the need for strict control of alloy composition and repeated heat treatment and plastic processing, so that the prepared aluminum alloy has both high strength and plasticity.

[0069] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the protection scope of the present application.

Claims

1. A method for simultaneously improving strength and ductility of an aluminum alloy, characterized by, The method comprises the following steps: (1) homogenizing and hot extruding the as-cast aluminum alloy in sequence to obtain an extruded rod; (2) solid solution treating, quenching and double-stage aging the extruded rod obtained in step (1) in sequence to obtain the aluminum alloy; the double-stage aging comprises first-stage aging and second-stage aging in sequence; the holding temperature of the first-stage aging is 110-130 DEG C, and the holding time of the first-stage aging is 60-180 min; the holding temperature of the second-stage aging is 170-200 DEG C, and the holding time of the second-stage aging is 420-480 min; the heating rate from the holding temperature of the first-stage aging to the holding temperature of the second-stage aging is 1-3 DEG C / min.

2. The method of claim 1, wherein, The holding temperature of the solid solution treatment in step (2) is 490-500 DEG C, and the holding time of the solid solution treatment is 60-70 min.

3. The method of claim 2, wherein, The heating rate to the holding temperature of the solid solution treatment is 2-3 DEG C / min.

4. The method of claim 1, wherein, The quenching process in step (2) comprises: transferring to a cooling medium of polyethylene oxide aqueous solution within 10 s at the holding temperature of the solid solution treatment to cool to room temperature.

5. The method of claim 4, wherein, The mass concentration of polyethylene oxide in the polyethylene oxide aqueous solution is 0.1-0.15%, and the relative molecular mass of the polyethylene oxide is 4.5×10 6 ~5.5×10 6 .

6. The method of claim 1, wherein, The holding temperature of the homogenization treatment in step (1) is 483-503 DEG C, and the holding time of the homogenization treatment is 16-18 h.

7. The method of claim 1, wherein, The temperature of the hot extrusion in step (1) is 350-450 DEG C.

8. The method of claim 1 or 7, wherein, The extrusion ratio of the hot extrusion in step (1) is (14-18):1, the extrusion speed of the hot extrusion is 1.5-2.5 mm / s, and the direction of the hot extrusion is positive extrusion.

9. The method of claim 1, wherein, The grade of the as-cast aluminum alloy in step (1) comprises 2024, 2124 or 2219 aluminum alloy.

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